Merge pull request #315 from Psychotoxical/feat/waveform-loudness-cache

feat(playback): waveform loudness cache (EBU R128 + persistent analysis)

src-tauri/Cargo.lock

@@ -944,6 +944,15 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "dasp_frame"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2a3937f5fe2135702897535c8d4a5553f8b116f76c1529088797f2eee7c5cd6"
+dependencies = [
+ "dasp_sample",
+]
+
 [[package]]
 name = "dasp_sample"
 version = "0.11.0"
@@ -1169,6 +1178,18 @@ version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d0881ea181b1df73ff77ffaaf9c7544ecc11e82fba9b5f27b262a3c73a332555"
 
+[[package]]
+name = "ebur128"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e227cc62d64d6fe01abbef48134b9c1f17d470cef1e7a56337ad05b1f81df7f9"
+dependencies = [
+ "bitflags 1.3.2",
+ "dasp_frame",
+ "dasp_sample",
+ "smallvec",
+]
+
 [[package]]
 name = "either"
 version = "1.15.0"
@@ -1302,6 +1323,18 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "af9673d8203fcb076b19dfd17e38b3d4ae9f44959416ea532ce72415a6020365"
 
+[[package]]
+name = "fallible-iterator"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2acce4a10f12dc2fb14a218589d4f1f62ef011b2d0cc4b3cb1bba8e94da14649"
+
+[[package]]
+name = "fallible-streaming-iterator"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7360491ce676a36bf9bb3c56c1aa791658183a54d2744120f27285738d90465a"
+
 [[package]]
 name = "fastrand"
 version = "1.9.0"
@@ -1908,6 +1941,15 @@ version = "0.17.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4f467dd6dccf739c208452f8014c75c18bb8301b050ad1cfb27153803edb0f51"
 
+[[package]]
+name = "hashlink"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7382cf6263419f2d8df38c55d7da83da5c18aef87fc7a7fc1fb1e344edfe14c1"
+dependencies = [
+ "hashbrown 0.15.5",
+]
+
 [[package]]
 name = "heck"
 version = "0.4.1"
@@ -2548,6 +2590,17 @@ dependencies = [
  "redox_syscall 0.7.4",
 ]
 
+[[package]]
+name = "libsqlite3-sys"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "133c182a6a2c87864fe97778797e46c7e999672690dc9fa3ee8e241aa4a9c13f"
+dependencies = [
+ "cc",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.3.8"
@@ -3657,6 +3710,7 @@ version = "1.43.0"
 dependencies = [
  "biquad",
  "discord-rich-presence",
+ "ebur128",
  "futures-util",
  "id3",
  "libc",
@@ -3665,6 +3719,7 @@ dependencies = [
  "reqwest 0.12.28",
  "ringbuf",
  "rodio",
+ "rusqlite",
  "serde",
  "serde_json",
  "souvlaki",
@@ -4116,6 +4171,20 @@ dependencies = [
  "thiserror 1.0.69",
 ]
 
+[[package]]
+name = "rusqlite"
+version = "0.37.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "165ca6e57b20e1351573e3729b958bc62f0e48025386970b6e4d29e7a7e71f3f"
+dependencies = [
+ "bitflags 2.11.1",
+ "fallible-iterator",
+ "fallible-streaming-iterator",
+ "hashlink",
+ "libsqlite3-sys",
+ "smallvec",
+]
+
 [[package]]
 name = "rustc-hash"
 version = "2.1.2"
@@ -6115,6 +6184,12 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "vcpkg"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
+
 [[package]]
 name = "version-compare"
 version = "0.2.1"

src-tauri/Cargo.toml

@@ -49,6 +49,8 @@ lofty = "0.22"
 sysinfo = { version = "0.33", default-features = false, features = ["disk"] }
 id3 = "1.16.4"
 symphonia-adapter-libopus = "0.2.7"
+rusqlite = { version = "0.37", features = ["bundled"] }
+ebur128 = "0.1"
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"

src-tauri/patches/cpal-0.15.3/src/host/alsa/mod.rs

@@ -1063,10 +1063,11 @@ fn set_hw_params_from_format(
             hw_params.set_buffer_size(v as alsa::pcm::Frames)?;
         }
         BufferSize::Default => {
-            // These values together represent a moderate latency and wakeup interval.
+            // Larger buffer than upstream cpal default: after Symphonia seeks or CPU
-            // Without them, we are at the mercy of the device
+            // spikes (analysis, demux) the mixer needs more margin before ALSA underruns.
-            hw_params.set_period_time_near(25_000, alsa::ValueOr::Nearest)?;
+            // ~40 ms period, ~200 ms total buffer (device may round to nearest supported).
-            hw_params.set_buffer_time_near(100_000, alsa::ValueOr::Nearest)?;
+            hw_params.set_period_time_near(40_000, alsa::ValueOr::Nearest)?;
+            hw_params.set_buffer_time_near(200_000, alsa::ValueOr::Nearest)?;
         }
     }
 

src-tauri/src/analysis_cache.rs

@@ -0,0 +1,824 @@
+use std::path::PathBuf;
+use std::io::Cursor;
+use std::sync::Mutex;
+use std::time::{Instant, SystemTime, UNIX_EPOCH};
+
+use ebur128::{EbuR128, Mode as Ebur128Mode};
+use rusqlite::{params, Connection, OptionalExtension};
+use symphonia::core::audio::SampleBuffer;
+use symphonia::core::codecs::{CODEC_TYPE_NULL, DecoderOptions};
+use symphonia::core::errors::Error as SymphoniaError;
+use symphonia::core::formats::FormatOptions;
+use symphonia::core::io::MediaSourceStream;
+use symphonia::core::meta::MetadataOptions;
+use symphonia::core::probe::Hint;
+use tauri::Manager;
+
+pub const WAVEFORM_ALGO_VERSION: i64 = 3;
+pub const LOUDNESS_ALGO_VERSION: i64 = 1;
+
+#[derive(Debug, Clone)]
+pub struct TrackKey {
+    pub track_id: String,
+    pub md5_16kb: String,
+}
+
+#[derive(Debug, Clone)]
+pub struct WaveformEntry {
+    pub bins: Vec<u8>,
+    pub bin_count: i64,
+    pub is_partial: bool,
+    pub known_until_sec: f64,
+    pub duration_sec: f64,
+    pub updated_at: i64,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Clone)]
+pub struct LoudnessEntry {
+    pub integrated_lufs: f64,
+    pub true_peak: f64,
+    pub recommended_gain_db: f64,
+    pub target_lufs: f64,
+    pub updated_at: i64,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Clone)]
+pub struct LoudnessSnapshot {
+    pub integrated_lufs: f64,
+    pub true_peak: f64,
+    pub recommended_gain_db: f64,
+    pub target_lufs: f64,
+    pub updated_at: i64,
+}
+
+pub struct AnalysisCache {
+    conn: Mutex<Connection>,
+}
+
+/// Ranged HTTP seeding uses `stream:<subsonicId>` (see `playback_identity`); backfill
+/// and IPC often use the bare `<subsonicId>`. Rows may exist under either key.
+fn track_id_cache_variants(id: &str) -> Vec<String> {
+    let mut out = vec![id.to_string()];
+    if let Some(bare) = id.strip_prefix("stream:") {
+        if !bare.is_empty() {
+            out.push(bare.to_string());
+        }
+    } else {
+        out.push(format!("stream:{id}"));
+    }
+    out
+}
+
+impl AnalysisCache {
+    pub fn init(app: &tauri::AppHandle) -> Result<Self, String> {
+        let db_path = analysis_db_path(app)?;
+        if let Some(parent) = db_path.parent() {
+            std::fs::create_dir_all(parent).map_err(|e| e.to_string())?;
+        }
+        let conn = Connection::open(db_path).map_err(|e| e.to_string())?;
+        configure_connection(&conn).map_err(|e| e.to_string())?;
+        migrate_schema(&conn).map_err(|e| e.to_string())?;
+        Ok(Self { conn: Mutex::new(conn) })
+    }
+
+    /// Remove all `loudness_cache` rows for this logical track (bare id and `stream:` variant).
+    pub fn delete_loudness_for_track_id(&self, track_id: &str) -> Result<u64, String> {
+        if track_id.trim().is_empty() {
+            return Ok(0);
+        }
+        let conn = self
+            .conn
+            .lock()
+            .map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        let mut total: u64 = 0;
+        for tid in track_id_cache_variants(track_id) {
+            let n = conn
+                .execute("DELETE FROM loudness_cache WHERE track_id = ?1", params![tid])
+                .map_err(|e| e.to_string())?;
+            total = total.saturating_add(n as u64);
+        }
+        Ok(total)
+    }
+
+    /// Remove all cached waveform rows across all tracks/variants.
+    pub fn delete_all_waveforms(&self) -> Result<u64, String> {
+        let conn = self
+            .conn
+            .lock()
+            .map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        let n = conn
+            .execute("DELETE FROM waveform_cache", [])
+            .map_err(|e| e.to_string())?;
+        Ok(n as u64)
+    }
+
+    pub fn touch_track_status(&self, key: &TrackKey, status: &str) -> Result<(), String> {
+        let now = now_unix_ts();
+        let conn = self.conn.lock().map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        conn.execute(
+            r#"
+            INSERT INTO analysis_track (
+                track_id, md5_16kb, status, waveform_algo_version, loudness_algo_version, updated_at
+            ) VALUES (?1, ?2, ?3, ?4, ?5, ?6)
+            ON CONFLICT(track_id, md5_16kb) DO UPDATE SET
+                status = excluded.status,
+                waveform_algo_version = excluded.waveform_algo_version,
+                loudness_algo_version = excluded.loudness_algo_version,
+                updated_at = excluded.updated_at
+            "#,
+            params![
+                key.track_id,
+                key.md5_16kb,
+                status,
+                WAVEFORM_ALGO_VERSION,
+                LOUDNESS_ALGO_VERSION,
+                now
+            ],
+        )
+        .map_err(|e| e.to_string())?;
+        Ok(())
+    }
+
+    pub fn upsert_waveform(&self, key: &TrackKey, entry: &WaveformEntry) -> Result<(), String> {
+        let conn = self.conn.lock().map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        conn.execute(
+            r#"
+            INSERT INTO waveform_cache (
+                track_id, md5_16kb, bins, bin_count, is_partial, known_until_sec, duration_sec, updated_at
+            ) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8)
+            ON CONFLICT(track_id, md5_16kb) DO UPDATE SET
+                bins = excluded.bins,
+                bin_count = excluded.bin_count,
+                is_partial = excluded.is_partial,
+                known_until_sec = excluded.known_until_sec,
+                duration_sec = excluded.duration_sec,
+                updated_at = excluded.updated_at
+            "#,
+            params![
+                key.track_id,
+                key.md5_16kb,
+                entry.bins,
+                entry.bin_count,
+                if entry.is_partial { 1 } else { 0 },
+                entry.known_until_sec,
+                entry.duration_sec,
+                entry.updated_at
+            ],
+        )
+        .map_err(|e| e.to_string())?;
+        Ok(())
+    }
+
+    pub fn upsert_loudness(&self, key: &TrackKey, entry: &LoudnessEntry) -> Result<(), String> {
+        let conn = self.conn.lock().map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        conn.execute(
+            r#"
+            INSERT INTO loudness_cache (
+                track_id, md5_16kb, integrated_lufs, true_peak, recommended_gain_db, target_lufs, updated_at
+            ) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7)
+            ON CONFLICT(track_id, md5_16kb, target_lufs) DO UPDATE SET
+                integrated_lufs = excluded.integrated_lufs,
+                true_peak = excluded.true_peak,
+                recommended_gain_db = excluded.recommended_gain_db,
+                updated_at = excluded.updated_at
+            "#,
+            params![
+                key.track_id,
+                key.md5_16kb,
+                entry.integrated_lufs,
+                entry.true_peak,
+                entry.recommended_gain_db,
+                entry.target_lufs,
+                entry.updated_at
+            ],
+        )
+        .map_err(|e| e.to_string())?;
+        Ok(())
+    }
+
+    pub fn get_waveform(&self, key: &TrackKey) -> Result<Option<WaveformEntry>, String> {
+        let conn = self.conn.lock().map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        conn.query_row(
+            r#"
+            SELECT w.bins, w.bin_count, w.is_partial, w.known_until_sec, w.duration_sec, w.updated_at
+            FROM waveform_cache w
+            JOIN analysis_track a
+              ON a.track_id = w.track_id
+             AND a.md5_16kb = w.md5_16kb
+            WHERE w.track_id = ?1
+              AND w.md5_16kb = ?2
+              AND a.waveform_algo_version = ?3
+            "#,
+            params![key.track_id, key.md5_16kb, WAVEFORM_ALGO_VERSION],
+            |row| {
+                Ok(WaveformEntry {
+                    bins: row.get(0)?,
+                    bin_count: row.get(1)?,
+                    is_partial: row.get::<_, i64>(2)? != 0,
+                    known_until_sec: row.get(3)?,
+                    duration_sec: row.get(4)?,
+                    updated_at: row.get(5)?,
+                })
+            },
+        )
+        .optional()
+        .map_err(|e| e.to_string())
+    }
+
+    pub fn get_latest_waveform_for_track(&self, track_id: &str) -> Result<Option<WaveformEntry>, String> {
+        let conn = self.conn.lock().map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        const SQL: &str = r#"
+            SELECT w.bins, w.bin_count, w.is_partial, w.known_until_sec, w.duration_sec, w.updated_at
+            FROM waveform_cache w
+            JOIN analysis_track a
+              ON a.track_id = w.track_id
+             AND a.md5_16kb = w.md5_16kb
+            WHERE w.track_id = ?1
+              AND a.waveform_algo_version = ?2
+            ORDER BY w.updated_at DESC
+            LIMIT 1
+            "#;
+        for tid in track_id_cache_variants(track_id) {
+            let row = conn
+                .query_row(
+                    SQL,
+                    params![tid, WAVEFORM_ALGO_VERSION],
+                    |row| {
+                        Ok(WaveformEntry {
+                            bins: row.get(0)?,
+                            bin_count: row.get(1)?,
+                            is_partial: row.get::<_, i64>(2)? != 0,
+                            known_until_sec: row.get(3)?,
+                            duration_sec: row.get(4)?,
+                            updated_at: row.get(5)?,
+                        })
+                    },
+                )
+                .optional()
+                .map_err(|e| e.to_string())?;
+            if row.is_some() {
+                return Ok(row);
+            }
+        }
+        Ok(None)
+    }
+
+    pub fn get_latest_loudness_for_track(&self, track_id: &str) -> Result<Option<LoudnessSnapshot>, String> {
+        let conn = self.conn.lock().map_err(|_| "analysis_cache lock poisoned".to_string())?;
+        const SQL: &str = r#"
+            SELECT l.integrated_lufs, l.true_peak, l.recommended_gain_db, l.target_lufs, l.updated_at
+            FROM loudness_cache l
+            JOIN analysis_track a
+              ON a.track_id = l.track_id
+             AND a.md5_16kb = l.md5_16kb
+            WHERE l.track_id = ?1
+              AND a.loudness_algo_version = ?2
+            ORDER BY l.updated_at DESC
+            LIMIT 1
+            "#;
+        for tid in track_id_cache_variants(track_id) {
+            let row = conn
+                .query_row(
+                    SQL,
+                    params![tid, LOUDNESS_ALGO_VERSION],
+                    |row| {
+                        Ok(LoudnessSnapshot {
+                            integrated_lufs: row.get(0)?,
+                            true_peak: row.get(1)?,
+                            recommended_gain_db: row.get(2)?,
+                            target_lufs: row.get(3)?,
+                            updated_at: row.get(4)?,
+                        })
+                    },
+                )
+                .optional()
+                .map_err(|e| e.to_string())?;
+            if row.is_some() {
+                return Ok(row);
+            }
+        }
+        Ok(None)
+    }
+}
+
+pub fn recommended_gain_for_target(integrated_lufs: f64, true_peak: f64, target_lufs: f64) -> f64 {
+    let mut recommended_gain_db = target_lufs - integrated_lufs;
+    if true_peak > 0.0 {
+        let true_peak_dbtp = 20.0 * true_peak.log10();
+        let max_gain_db = -1.0 - true_peak_dbtp;
+        if recommended_gain_db > max_gain_db {
+            recommended_gain_db = max_gain_db;
+        }
+    }
+    recommended_gain_db.clamp(-24.0, 24.0)
+}
+
+/// Result of [`seed_from_bytes`]: callers use it to avoid redundant UI events.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SeedFromBytesOutcome {
+    /// Wrote waveform (and loudness when PCM decode succeeded).
+    Upserted,
+    /// Same `track_id` + `md5_16kb` already had a non-empty waveform for this algo version.
+    SkippedWaveformCacheHit,
+    /// `AnalysisCache` was not registered on the app handle.
+    SkippedNoAnalysisCache,
+}
+
+pub fn seed_from_bytes(
+    app: &tauri::AppHandle,
+    track_id: &str,
+    bytes: &[u8],
+) -> Result<SeedFromBytesOutcome, String> {
+    let started = Instant::now();
+    let Some(cache) = app.try_state::<AnalysisCache>() else {
+        crate::app_deprintln!(
+            "[analysis][waveform] build skip track_id={} reason=no_analysis_cache bytes={}",
+            track_id,
+            bytes.len()
+        );
+        return Ok(SeedFromBytesOutcome::SkippedNoAnalysisCache);
+    };
+    let key = TrackKey {
+        track_id: track_id.to_string(),
+        md5_16kb: md5_first_16kb(bytes),
+    };
+    if let Some(existing) = cache.get_waveform(&key)? {
+        if !existing.bins.is_empty() {
+            crate::app_deprintln!(
+                "[analysis][waveform] build skip track_id={} reason=waveform_cache_hit md5_16kb={} bins_len={} elapsed_ms={}",
+                track_id,
+                key.md5_16kb,
+                existing.bins.len(),
+                started.elapsed().as_millis()
+            );
+            return Ok(SeedFromBytesOutcome::SkippedWaveformCacheHit);
+        }
+    }
+    crate::app_deprintln!(
+        "[analysis][waveform] build start track_id={} bytes={} md5_16kb={}",
+        track_id,
+        bytes.len(),
+        key.md5_16kb
+    );
+
+    let build = (|| -> Result<(bool, usize), String> {
+        cache.touch_track_status(&key, "queued")?;
+
+        let (wf_bins, loudness_opt, used_pcm_decode) = match analyze_loudness_and_waveform(bytes, -16.0, 500) {
+            Some((integrated_lufs, true_peak, recommended_gain_db, target_lufs, bins)) => {
+                (
+                    bins,
+                    Some((integrated_lufs, true_peak, recommended_gain_db, target_lufs)),
+                    true,
+                )
+            }
+            None => (derive_waveform_bins(bytes, 500), None, false),
+        };
+        let bins_len = wf_bins.len();
+        let waveform = WaveformEntry {
+            bins: wf_bins,
+            bin_count: 500,
+            is_partial: false,
+            known_until_sec: 0.0,
+            duration_sec: 0.0,
+            updated_at: now_unix_ts(),
+        };
+        cache.upsert_waveform(&key, &waveform)?;
+
+        if let Some((integrated_lufs, true_peak, recommended_gain_db, target_lufs)) = loudness_opt {
+            let loudness = LoudnessEntry {
+                integrated_lufs,
+                true_peak,
+                recommended_gain_db,
+                target_lufs,
+                updated_at: now_unix_ts(),
+            };
+            cache.upsert_loudness(&key, &loudness)?;
+        }
+
+        cache.touch_track_status(&key, "ready")?;
+        Ok((used_pcm_decode, bins_len))
+    })();
+
+    let elapsed_ms = started.elapsed().as_millis();
+    match &build {
+        Ok((used_pcm_decode, bins_len)) => {
+            crate::app_deprintln!(
+                "[analysis][waveform] build done track_id={} elapsed_ms={} path={} bins_len={}",
+                track_id,
+                elapsed_ms,
+                if *used_pcm_decode {
+                    "pcm_ebur128"
+                } else {
+                    "byte_envelope"
+                },
+                bins_len
+            );
+        }
+        Err(e) => {
+            crate::app_deprintln!(
+                "[analysis][waveform] build failed track_id={} elapsed_ms={} err={}",
+                track_id,
+                elapsed_ms,
+                e
+            );
+        }
+    }
+
+    match build {
+        Ok(_) => Ok(SeedFromBytesOutcome::Upserted),
+        Err(e) => Err(e),
+    }
+}
+
+fn now_unix_ts() -> i64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_secs() as i64)
+        .unwrap_or(0)
+}
+
+fn md5_first_16kb(bytes: &[u8]) -> String {
+    let n = bytes.len().min(16 * 1024);
+    format!("{:x}", md5::compute(&bytes[..n]))
+}
+
+fn derive_waveform_bins(bytes: &[u8], bin_count: usize) -> Vec<u8> {
+    if bin_count == 0 || bytes.is_empty() {
+        return Vec::new();
+    }
+    let mut out = vec![0u8; bin_count];
+    for (i, slot) in out.iter_mut().enumerate() {
+        let start = i * bytes.len() / bin_count;
+        let end = ((i + 1) * bytes.len() / bin_count).max(start + 1).min(bytes.len());
+        let mut peak: u8 = 0;
+        for &b in &bytes[start..end] {
+            let centered = if b >= 128 { b - 128 } else { 128 - b };
+            if centered > peak {
+                peak = centered;
+            }
+        }
+        *slot = ((peak as f32 / 127.0).sqrt().clamp(0.0, 1.0) * 255.0) as u8;
+    }
+    out
+}
+
+struct PcmScanResult {
+    bins: Vec<u8>,
+    loudness: Option<(f64, f64, f64, f64)>,
+}
+
+/// Loudness (EBU R128) plus PCM waveform bins in one decode pass after a frame count.
+fn analyze_loudness_and_waveform(
+    bytes: &[u8],
+    target_lufs: f64,
+    bin_count: usize,
+) -> Option<(f64, f64, f64, f64, Vec<u8>)> {
+    if bytes.is_empty() || bin_count == 0 {
+        return None;
+    }
+    let (decoded_frames, timeline_hint) = count_mono_frames_from_audio_bytes(bytes)?;
+    if decoded_frames == 0 {
+        return None;
+    }
+    let scanned = decode_scan_pcm(bytes, bin_count, decoded_frames, timeline_hint, Some(target_lufs))?;
+    let (i, t, r, tgt) = scanned.loudness?;
+    Some((i, t, r, tgt, scanned.bins))
+}
+
+/// Returns `(decoded_mono_frames, container_timeline_frames)` where the second is
+/// `codec_params.n_frames` when the container reports total track length — used
+/// as a **fixed** waveform time axis so partial decodes do not remap every bin
+/// when the buffer grows.
+fn count_mono_frames_from_audio_bytes(bytes: &[u8]) -> Option<(u64, Option<u64>)> {
+    let source = Box::new(Cursor::new(bytes.to_vec()));
+    let mss = MediaSourceStream::new(source, Default::default());
+    let hint = Hint::new();
+    let probed = symphonia::default::get_probe()
+        .format(&hint, mss, &FormatOptions::default(), &MetadataOptions::default())
+        .ok()?;
+    let mut format = probed.format;
+    let track = format
+        .default_track()
+        .filter(|t| t.codec_params.codec != CODEC_TYPE_NULL)
+        .or_else(|| {
+            format.tracks().iter().find(|t| {
+                t.codec_params.codec != CODEC_TYPE_NULL
+                    && t.codec_params.sample_rate.is_some()
+                    && t.codec_params.channels.is_some()
+            })
+        })
+        .or_else(|| format.tracks().iter().find(|t| t.codec_params.codec != CODEC_TYPE_NULL))?;
+    let track_id = track.id;
+    let timeline_hint = track.codec_params.n_frames.filter(|&n| n > 0);
+    let codec_params = track.codec_params.clone();
+    let mut decoder = symphonia::default::get_codecs()
+        .make(&codec_params, &DecoderOptions::default())
+        .ok()?;
+
+    let mut total: u64 = 0;
+    let mut loop_i: u32 = 0;
+    loop {
+        let packet = match format.next_packet() {
+            Ok(packet) => packet,
+            Err(_) => break,
+        };
+        if packet.track_id() != track_id {
+            continue;
+        }
+        let decoded = match decoder.decode(&packet) {
+            Ok(buf) => buf,
+            Err(SymphoniaError::DecodeError(_)) => continue,
+            Err(SymphoniaError::ResetRequired) => break,
+            Err(_) => break,
+        };
+        let spec = *decoded.spec();
+        let n_ch = spec.channels.count();
+        if n_ch == 0 {
+            continue;
+        }
+        let mut samples = SampleBuffer::<f32>::new(decoded.capacity() as u64, spec);
+        samples.copy_interleaved_ref(decoded);
+        let n = samples.samples().len();
+        if n < n_ch || n % n_ch != 0 {
+            continue;
+        }
+        total += (n / n_ch) as u64;
+        loop_i = loop_i.wrapping_add(1);
+        if loop_i % 128 == 0 {
+            std::thread::yield_now();
+        }
+    }
+    if total == 0 {
+        None
+    } else {
+        Some((total, timeline_hint))
+    }
+}
+
+fn normalize_peak_bins(bin_max: &[f32]) -> Vec<u8> {
+    let bin_count = bin_max.len();
+    if bin_count == 0 {
+        return Vec::new();
+    }
+    let mut sorted: Vec<f32> = bin_max.to_vec();
+    sorted.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
+    let p5 = sorted[(sorted.len() * 5 / 100).min(sorted.len().saturating_sub(1))];
+    let p99 = sorted[(sorted.len() * 99 / 100).min(sorted.len().saturating_sub(1))];
+    let range = (p99 - p5).max(1e-8);
+    let mut out = vec![0u8; bin_count];
+    for i in 0..bin_count {
+        let t = ((bin_max[i] - p5) / range).clamp(0.0, 1.0);
+        let shaped = t.powf(0.52);
+        out[i] = (8.0 + shaped * 247.0).min(255.0) as u8;
+    }
+    out
+}
+
+fn decode_scan_pcm(
+    bytes: &[u8],
+    bin_count: usize,
+    decoded_frames: u64,
+    timeline_hint: Option<u64>,
+    loudness_target_lufs: Option<f64>,
+) -> Option<PcmScanResult> {
+    let source = Box::new(Cursor::new(bytes.to_vec()));
+    let mss = MediaSourceStream::new(source, Default::default());
+    let hint = Hint::new();
+    let probed = symphonia::default::get_probe()
+        .format(&hint, mss, &FormatOptions::default(), &MetadataOptions::default())
+        .ok()?;
+    let mut format = probed.format;
+    let track = format
+        .default_track()
+        .filter(|t| t.codec_params.codec != CODEC_TYPE_NULL)
+        .or_else(|| {
+            format.tracks().iter().find(|t| {
+                t.codec_params.codec != CODEC_TYPE_NULL
+                    && t.codec_params.sample_rate.is_some()
+                    && t.codec_params.channels.is_some()
+            })
+        })
+        .or_else(|| format.tracks().iter().find(|t| t.codec_params.codec != CODEC_TYPE_NULL))?;
+    let track_id = track.id;
+    let codec_params = track.codec_params.clone();
+    let mut decoder = match symphonia::default::get_codecs().make(&codec_params, &DecoderOptions::default()) {
+        Ok(v) => v,
+        Err(e) => {
+            crate::app_deprintln!("[analysis] decoder make failed: {}", e);
+            return None;
+        }
+    };
+
+    let mut bin_max = vec![0.0f32; bin_count];
+    let mut ebu: Option<EbuR128> = None;
+    let mut ebu_channels: u32 = 0;
+    let mut sample_peak_abs = 0.0_f64;
+    let mut fed_any_frames = false;
+    let mut sample_idx: u64 = 0;
+    let mut loop_i: u32 = 0;
+    // Fixed timeline from metadata when available; otherwise fall back to decoded
+    // length (full-buffer analysis only — partial byte windows still shift, but
+    // then we usually lack n_frames anyway).
+    let bin_grid_frames = timeline_hint
+        .map(|n| n.max(decoded_frames))
+        .unwrap_or(decoded_frames)
+        .max(1);
+
+    loop {
+        let packet = match format.next_packet() {
+            Ok(packet) => packet,
+            Err(_) => break,
+        };
+        if packet.track_id() != track_id {
+            continue;
+        }
+        let decoded = match decoder.decode(&packet) {
+            Ok(buf) => buf,
+            Err(SymphoniaError::DecodeError(_)) => continue,
+            Err(SymphoniaError::ResetRequired) => break,
+            Err(_) => break,
+        };
+
+        let spec = *decoded.spec();
+        let n_ch = spec.channels.count();
+        if n_ch == 0 {
+            continue;
+        }
+
+        if loudness_target_lufs.is_some() && ebu.is_none() {
+            let ch = spec.channels.count() as u32;
+            let sr = spec.rate;
+            match EbuR128::new(ch, sr, Ebur128Mode::I | Ebur128Mode::TRUE_PEAK) {
+                Ok(v) => {
+                    ebu = Some(v);
+                    ebu_channels = ch;
+                }
+                Err(e) => {
+                    crate::app_deprintln!(
+                        "[analysis] EbuR128 init failed: channels={} sample_rate={} err={}",
+                        ch,
+                        sr,
+                        e
+                    );
+                    return None;
+                }
+            }
+        }
+
+        let mut samples = SampleBuffer::<f32>::new(decoded.capacity() as u64, spec);
+        samples.copy_interleaved_ref(decoded);
+        let slice = samples.samples();
+        if slice.len() < n_ch || slice.len() % n_ch != 0 {
+            continue;
+        }
+        let frames = slice.len() / n_ch;
+
+        for f in 0..frames {
+            let base = f * n_ch;
+            let mut acc = 0.0f32;
+            for c in 0..n_ch {
+                acc += slice[base + c];
+            }
+            let mono = acc / (n_ch as f32);
+            let mag = mono.abs();
+            if mag.is_finite() {
+                let bin = ((sample_idx * bin_count as u64) / bin_grid_frames) as usize;
+                let bin = bin.min(bin_count.saturating_sub(1));
+                bin_max[bin] = bin_max[bin].max(mag);
+            }
+            for c in 0..n_ch {
+                let v = (slice[base + c] as f64).abs();
+                if v.is_finite() && v > sample_peak_abs {
+                    sample_peak_abs = v;
+                }
+            }
+            sample_idx += 1;
+        }
+
+        if loudness_target_lufs.is_some() {
+            if let Some(e) = ebu.as_mut() {
+                match e.add_frames_f32(samples.samples()) {
+                    Ok(_) => fed_any_frames = true,
+                    Err(err) => {
+                        crate::app_deprintln!("[analysis] loudness add_frames failed: {}", err);
+                        return None;
+                    }
+                }
+            }
+        }
+
+        loop_i = loop_i.wrapping_add(1);
+        if loop_i % 128 == 0 {
+            std::thread::yield_now();
+        }
+    }
+
+    let bins = normalize_peak_bins(&bin_max);
+
+    let loudness = if let Some(target_lufs) = loudness_target_lufs {
+        if !fed_any_frames {
+            crate::app_deprintln!("[analysis] loudness failed: no decoded frames");
+            return None;
+        }
+        let Some(ebu) = ebu else {
+            crate::app_deprintln!("[analysis] loudness failed: ebu not initialized");
+            return None;
+        };
+        let integrated_lufs = match ebu.loudness_global() {
+            Ok(v) => v,
+            Err(e) => {
+                crate::app_deprintln!("[analysis] loudness_global failed: {}", e);
+                return None;
+            }
+        };
+        if !integrated_lufs.is_finite() {
+            crate::app_deprintln!("[analysis] loudness failed: integrated_lufs not finite");
+            return None;
+        }
+        let mut true_peak = 0.0_f64;
+        let mut true_peak_ok = true;
+        for ch in 0..ebu_channels {
+            match ebu.true_peak(ch) {
+                Ok(v) if v.is_finite() && v > true_peak => true_peak = v,
+                Ok(_) => {}
+                Err(e) => {
+                    true_peak_ok = false;
+                    crate::app_deprintln!("[analysis] true_peak unavailable: {}", e);
+                    break;
+                }
+            }
+        }
+        if !true_peak_ok {
+            true_peak = sample_peak_abs;
+        }
+        let recommended_gain_db =
+            recommended_gain_for_target(integrated_lufs, true_peak, target_lufs);
+        Some((integrated_lufs, true_peak, recommended_gain_db, target_lufs))
+    } else {
+        None
+    };
+
+    Some(PcmScanResult { bins, loudness })
+}
+
+fn analysis_db_path(app: &tauri::AppHandle) -> Result<PathBuf, String> {
+    let base = app
+        .path()
+        .app_config_dir()
+        .map_err(|e| e.to_string())?;
+    Ok(base.join("audio-analysis.sqlite"))
+}
+
+fn configure_connection(conn: &Connection) -> rusqlite::Result<()> {
+    conn.pragma_update(None, "journal_mode", "WAL")?;
+    conn.pragma_update(None, "synchronous", "NORMAL")?;
+    conn.pragma_update(None, "temp_store", "MEMORY")?;
+    conn.pragma_update(None, "foreign_keys", "ON")?;
+    Ok(())
+}
+
+fn migrate_schema(conn: &Connection) -> rusqlite::Result<()> {
+    conn.execute_batch(
+        r#"
+        CREATE TABLE IF NOT EXISTS analysis_track (
+            track_id TEXT NOT NULL,
+            md5_16kb TEXT NOT NULL,
+            status TEXT NOT NULL,
+            waveform_algo_version INTEGER NOT NULL,
+            loudness_algo_version INTEGER NOT NULL,
+            updated_at INTEGER NOT NULL,
+            PRIMARY KEY (track_id, md5_16kb)
+        );
+
+        CREATE TABLE IF NOT EXISTS waveform_cache (
+            track_id TEXT NOT NULL,
+            md5_16kb TEXT NOT NULL,
+            bins BLOB NOT NULL,
+            bin_count INTEGER NOT NULL,
+            is_partial INTEGER NOT NULL,
+            known_until_sec REAL NOT NULL,
+            duration_sec REAL NOT NULL,
+            updated_at INTEGER NOT NULL,
+            PRIMARY KEY (track_id, md5_16kb)
+        );
+
+        CREATE TABLE IF NOT EXISTS loudness_cache (
+            track_id TEXT NOT NULL,
+            md5_16kb TEXT NOT NULL,
+            integrated_lufs REAL NOT NULL,
+            true_peak REAL NOT NULL,
+            recommended_gain_db REAL NOT NULL,
+            target_lufs REAL NOT NULL,
+            updated_at INTEGER NOT NULL,
+            PRIMARY KEY (track_id, md5_16kb, target_lufs)
+        );
+
+        CREATE INDEX IF NOT EXISTS idx_analysis_track_status
+            ON analysis_track(status);
+        "#,
+    )?;
+    Ok(())
+}

src-tauri/src/lib.rs

@@ -2,6 +2,7 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
 
 mod audio;
+mod analysis_cache;
 pub mod cli;
 mod discord;
 pub(crate) mod logging;
@@ -59,6 +60,12 @@ fn sync_cancel_flags() -> &'static Mutex<HashMap<String, Arc<AtomicBool>>> {
     FLAGS.get_or_init(|| Mutex::new(HashMap::new()))
 }
 
+/// Tracks analysis backfill jobs already running per track_id.
+fn analysis_backfill_inflight() -> &'static Mutex<std::collections::HashSet<String>> {
+    static SET: OnceLock<Mutex<std::collections::HashSet<String>>> = OnceLock::new();
+    SET.get_or_init(|| Mutex::new(std::collections::HashSet::new()))
+}
+
 /// Holds the live system-tray icon handle.  `None` means the tray is currently hidden/removed.
 /// Dropping the inner `TrayIcon` fully removes it from the OS notification area on all platforms.
 type TrayState = Mutex<Option<TrayIcon>>;
@@ -67,6 +74,34 @@ type TrayState = Mutex<Option<TrayIcon>>;
 /// `None` if souvlaki failed to initialize (e.g. no D-Bus session on Linux).
 type MprisControls = Mutex<Option<souvlaki::MediaControls>>;
 
+#[derive(serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+struct WaveformCachePayload {
+    bins: Vec<u8>,
+    bin_count: i64,
+    is_partial: bool,
+    known_until_sec: f64,
+    duration_sec: f64,
+    updated_at: i64,
+}
+
+#[derive(Clone, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+struct WaveformUpdatedPayload {
+    track_id: String,
+    is_partial: bool,
+}
+
+#[derive(serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+struct LoudnessCachePayload {
+    integrated_lufs: f64,
+    true_peak: f64,
+    recommended_gain_db: f64,
+    target_lufs: f64,
+    updated_at: i64,
+}
+
 #[tauri::command]
 fn greet(name: &str) -> String {
     format!("Hello, {}!", name)
@@ -1158,6 +1193,180 @@ fn check_dir_accessible(path: String) -> bool {
     std::path::Path::new(&path).is_dir()
 }
 
+#[tauri::command]
+fn analysis_get_waveform(
+    track_id: String,
+    md5_16kb: String,
+    cache: tauri::State<'_, analysis_cache::AnalysisCache>,
+) -> Result<Option<WaveformCachePayload>, String> {
+    let key = analysis_cache::TrackKey {
+        track_id: track_id.clone(),
+        md5_16kb: md5_16kb.clone(),
+    };
+    let row = cache.get_waveform(&key)?;
+    match &row {
+        Some(v) => {
+            crate::app_deprintln!(
+                "[analysis][waveform] db hit (exact key) track_id={} md5_16kb={} bins_len={} bin_count={} updated_at={}",
+                track_id,
+                md5_16kb,
+                v.bins.len(),
+                v.bin_count,
+                v.updated_at
+            );
+        }
+        None => {
+            crate::app_deprintln!(
+                "[analysis][waveform] db miss (exact key) track_id={} md5_16kb={}",
+                track_id,
+                md5_16kb
+            );
+        }
+    }
+    Ok(row.map(|v| WaveformCachePayload {
+        bins: v.bins,
+        bin_count: v.bin_count,
+        is_partial: v.is_partial,
+        known_until_sec: v.known_until_sec,
+        duration_sec: v.duration_sec,
+        updated_at: v.updated_at,
+    }))
+}
+
+#[tauri::command]
+fn analysis_get_waveform_for_track(
+    track_id: String,
+    cache: tauri::State<'_, analysis_cache::AnalysisCache>,
+) -> Result<Option<WaveformCachePayload>, String> {
+    let row = cache.get_latest_waveform_for_track(&track_id)?;
+    match &row {
+        Some(v) => {
+            crate::app_deprintln!(
+                "[analysis][waveform] db hit track_id={} bins_len={} bin_count={} updated_at={}",
+                track_id,
+                v.bins.len(),
+                v.bin_count,
+                v.updated_at
+            );
+        }
+        None => {
+            crate::app_deprintln!(
+                "[analysis][waveform] db miss track_id={}",
+                track_id
+            );
+        }
+    }
+    Ok(row.map(|v| WaveformCachePayload {
+        bins: v.bins,
+        bin_count: v.bin_count,
+        is_partial: v.is_partial,
+        known_until_sec: v.known_until_sec,
+        duration_sec: v.duration_sec,
+        updated_at: v.updated_at,
+    }))
+}
+
+#[tauri::command]
+fn analysis_get_loudness_for_track(
+    track_id: String,
+    target_lufs: Option<f64>,
+    cache: tauri::State<'_, analysis_cache::AnalysisCache>,
+) -> Result<Option<LoudnessCachePayload>, String> {
+    let row = cache.get_latest_loudness_for_track(&track_id)?;
+    Ok(row.map(|v| {
+        let requested_target = target_lufs.unwrap_or(v.target_lufs).clamp(-30.0, -8.0);
+        let recommended_gain_db = analysis_cache::recommended_gain_for_target(
+            v.integrated_lufs,
+            v.true_peak,
+            requested_target,
+        );
+        LoudnessCachePayload {
+        integrated_lufs: v.integrated_lufs,
+        true_peak: v.true_peak,
+        recommended_gain_db,
+        target_lufs: requested_target,
+        updated_at: v.updated_at,
+    }}))
+}
+
+#[tauri::command]
+fn analysis_delete_loudness_for_track(
+    track_id: String,
+    cache: tauri::State<'_, analysis_cache::AnalysisCache>,
+) -> Result<u64, String> {
+    cache.delete_loudness_for_track_id(&track_id)
+}
+
+#[tauri::command]
+fn analysis_delete_all_waveforms(
+    cache: tauri::State<'_, analysis_cache::AnalysisCache>,
+) -> Result<u64, String> {
+    cache.delete_all_waveforms()
+}
+
+#[tauri::command]
+fn analysis_enqueue_seed_from_url(
+    track_id: String,
+    url: String,
+    app: tauri::AppHandle,
+) -> Result<(), String> {
+    if track_id.trim().is_empty() || url.trim().is_empty() {
+        return Ok(());
+    }
+    if let Some(cache) = app.try_state::<analysis_cache::AnalysisCache>() {
+        if cache.get_latest_loudness_for_track(&track_id)?.is_some() {
+            crate::app_deprintln!(
+                "[analysis] backfill skip (already cached): {}",
+                track_id
+            );
+            return Ok(());
+        }
+    }
+    {
+        let mut inflight = analysis_backfill_inflight()
+            .lock()
+            .map_err(|_| "analysis backfill lock poisoned".to_string())?;
+        if inflight.contains(&track_id) {
+            return Ok(());
+        }
+        inflight.insert(track_id.clone());
+    }
+    let app_clone = app.clone();
+    tauri::async_runtime::spawn(async move {
+        crate::app_deprintln!("[analysis] backfill queued: {}", track_id);
+        let result = async {
+            let client = reqwest::Client::builder()
+                .user_agent(subsonic_wire_user_agent())
+                .timeout(std::time::Duration::from_secs(120))
+                .build()
+                .map_err(|e| e.to_string())?;
+            let response = client.get(&url).send().await.map_err(|e| e.to_string())?;
+            if !response.status().is_success() {
+                return Err(format!("HTTP {}", response.status().as_u16()));
+            }
+            let bytes = response.bytes().await.map_err(|e| e.to_string())?;
+            if bytes.is_empty() {
+                return Err("empty response".to_string());
+            }
+            let has_loudness = enqueue_analysis_seed(&app_clone, &track_id, &bytes)?;
+            Ok::<bool, String>(has_loudness)
+        }
+        .await;
+        match result {
+            Ok(has_loudness) => crate::app_deprintln!(
+                "[analysis] backfill ready: {} (has_loudness={})",
+                track_id,
+                has_loudness
+            ),
+            Err(e) => crate::app_eprintln!("[analysis] backfill failed for {}: {}", track_id, e),
+        }
+        if let Ok(mut inflight) = analysis_backfill_inflight().lock() {
+            inflight.remove(&track_id);
+        }
+    });
+    Ok(())
+}
+
 // ─── Offline Track Cache ──────────────────────────────────────────────────────
 
 /// Streams an HTTP response body directly to `dest_path` in small chunks.
@@ -1178,6 +1387,48 @@ async fn stream_to_file(response: reqwest::Response, dest_path: &std::path::Path
     Ok(())
 }
 
+fn enqueue_analysis_seed(app: &tauri::AppHandle, track_id: &str, bytes: &[u8]) -> Result<bool, String> {
+    let outcome = analysis_cache::seed_from_bytes(app, track_id, bytes).map_err(|e| {
+        crate::app_eprintln!("[analysis] failed to seed {}: {}", track_id, e);
+        e
+    })?;
+    if outcome == analysis_cache::SeedFromBytesOutcome::Upserted {
+        let _ = app.emit(
+            "analysis:waveform-updated",
+            WaveformUpdatedPayload {
+                track_id: track_id.to_string(),
+                is_partial: false,
+            },
+        );
+    }
+    let has_loudness = app
+        .try_state::<analysis_cache::AnalysisCache>()
+        .and_then(|cache| cache.get_latest_loudness_for_track(track_id).ok().flatten())
+        .is_some();
+    crate::app_deprintln!(
+        "[analysis] seed result track_id={} bytes={} has_loudness={}",
+        track_id,
+        bytes.len(),
+        has_loudness
+    );
+    Ok(has_loudness)
+}
+
+async fn enqueue_analysis_seed_from_file(
+    app: &tauri::AppHandle,
+    track_id: &str,
+    file_path: &std::path::Path,
+) {
+    let bytes = match tokio::fs::read(file_path).await {
+        Ok(v) => v,
+        Err(_) => return,
+    };
+    if bytes.is_empty() {
+        return;
+    }
+    let _ = enqueue_analysis_seed(app, track_id, &bytes);
+}
+
 /// Downloads a single track to the app's offline cache directory.
 /// Returns the absolute file path so TypeScript can store it and later
 /// construct a `psysonic-local://<path>` URL for the audio engine.
@@ -1244,6 +1495,8 @@ async fn download_track_offline(
         .await
         .map_err(|e| e.to_string())?;
 
+    enqueue_analysis_seed_from_file(&app, &track_id, &file_path).await;
+
     Ok(path_str)
 }
 
@@ -1792,6 +2045,8 @@ async fn download_track_hot_cache(
         .await
         .map_err(|e| e.to_string())?;
 
+    enqueue_analysis_seed_from_file(&app, &track_id, &file_path).await;
+
     let size = tokio::fs::metadata(&file_path)
         .await
         .map(|m| m.len())
@@ -1845,6 +2100,8 @@ async fn promote_stream_cache_to_hot_cache(
         .await
         .map_err(|e| e.to_string())?;
 
+    let _ = enqueue_analysis_seed(&app, &track_id, &bytes);
+
     let size = tokio::fs::metadata(&file_path)
         .await
         .map(|m| m.len())
@@ -3609,6 +3866,13 @@ pub fn run() {
         }))
 
         .setup(|app| {
+            // ── Analysis cache (SQLite) ───────────────────────────────────
+            {
+                let cache = analysis_cache::AnalysisCache::init(&app.handle())
+                    .map_err(|e| format!("analysis cache init failed: {e}"))?;
+                app.manage(cache);
+            }
+
             // ── Custom title bar on Linux ─────────────────────────────────
             // Remove OS window decorations on all Linux so the React TitleBar
             // can take over.  The frontend checks is_tiling_wm() to decide
@@ -3847,6 +4111,7 @@ pub fn run() {
             audio::audio_play_radio,
             audio::audio_set_crossfade,
             audio::audio_set_gapless,
+            audio::audio_set_normalization,
             audio::audio_list_devices,
             audio::audio_canonicalize_selected_device,
             audio::audio_default_output_device_name,
@@ -3878,6 +4143,12 @@ pub fn run() {
             fetch_json_url,
             fetch_icy_metadata,
             resolve_stream_url,
+            analysis_get_waveform,
+            analysis_get_waveform_for_track,
+            analysis_get_loudness_for_track,
+            analysis_delete_loudness_for_track,
+            analysis_delete_all_waveforms,
+            analysis_enqueue_seed_from_url,
             download_track_offline,
             delete_offline_track,
             get_offline_cache_size,

src/components/QueuePanel.tsx

@@ -1,4 +1,5 @@
-import React, { useState, useRef, useMemo, useEffect } from 'react';
+import React, { useState, useRef, useMemo, useEffect, useLayoutEffect } from 'react';
+import { createPortal } from 'react-dom';
 import { Track, usePlayerStore, songToTrack } from '../store/playerStore';
 import { useOrbitStore } from '../store/orbitStore';
 import OrbitGuestQueue from './OrbitGuestQueue';
@@ -304,6 +305,9 @@ function QueuePanelHostOrSolo() {
   const suppressNextAutoScrollRef = useRef(false);
 
   const playbackSource = usePlayerStore(s => s.currentPlaybackSource);
+  const normalizationNowDb = usePlayerStore(s => s.normalizationNowDb);
+  const normalizationTargetLufs = usePlayerStore(s => s.normalizationTargetLufs);
+  const normalizationEngineLive = usePlayerStore(s => s.normalizationEngineLive);
 
   const crossfadeEnabled = useAuthStore(s => s.crossfadeEnabled);
   const crossfadeSecs = useAuthStore(s => s.crossfadeSecs);
@@ -313,6 +317,8 @@ function QueuePanelHostOrSolo() {
   const setCrossfadeSecs = useAuthStore(s => s.setCrossfadeSecs);
   const setGaplessEnabled = useAuthStore(s => s.setGaplessEnabled);
   const setInfiniteQueueEnabled = useAuthStore(s => s.setInfiniteQueueEnabled);
+  const normalizationEngine = useAuthStore(s => s.normalizationEngine);
+  const replayGainMode = useAuthStore(s => s.replayGainMode);
 
   const activeTab  = useLyricsStore(s => s.activeTab);
   const setTab     = useLyricsStore(s => s.setTab);
@@ -320,10 +326,17 @@ function QueuePanelHostOrSolo() {
 
   const [showRemainingTime, setShowRemainingTime] = useState(false);
   const [showCrossfadePopover, setShowCrossfadePopover] = useState(false);
+  const [lufsTgtOpen, setLufsTgtOpen] = useState(false);
+  const [lufsTgtPopStyle, setLufsTgtPopStyle] = useState<React.CSSProperties>({});
+  const lufsTgtBtnRef = useRef<HTMLButtonElement>(null);
+  const lufsTgtMenuRef = useRef<HTMLDivElement>(null);
   const expandReplayGain = useThemeStore(s => s.expandReplayGain);
   const setExpandReplayGain = useThemeStore(s => s.setExpandReplayGain);
   const crossfadeBtnRef = useRef<HTMLButtonElement>(null);
   const crossfadePopoverRef = useRef<HTMLDivElement>(null);
+  const reanalyzeLoudnessForTrack = usePlayerStore(s => s.reanalyzeLoudnessForTrack);
+  const authLoudnessTargetLufs = useAuthStore(s => s.loudnessTargetLufs);
+  const setLoudnessTargetLufs = useAuthStore(s => s.setLoudnessTargetLufs);
 
   useEffect(() => {
     if (!showCrossfadePopover) return;
@@ -338,6 +351,64 @@ function QueuePanelHostOrSolo() {
     return () => document.removeEventListener('mousedown', handle);
   }, [showCrossfadePopover]);
 
+  useEffect(() => {
+    if (!lufsTgtOpen) return;
+    const handle = (e: MouseEvent) => {
+      if (
+        lufsTgtBtnRef.current?.contains(e.target as Node) ||
+        lufsTgtMenuRef.current?.contains(e.target as Node)
+      ) return;
+      setLufsTgtOpen(false);
+    };
+    document.addEventListener('mousedown', handle);
+    return () => document.removeEventListener('mousedown', handle);
+  }, [lufsTgtOpen]);
+
+  const updateLufsTgtPopStyle = () => {
+    if (!lufsTgtBtnRef.current) return;
+    const rect = lufsTgtBtnRef.current.getBoundingClientRect();
+    const MARGIN = 6;
+    const WIDTH = 160;
+    const MAX_H = 220;
+    const spaceBelow = window.innerHeight - rect.bottom - MARGIN;
+    const spaceAbove = rect.top - MARGIN;
+    const useAbove = spaceBelow < 120 && spaceAbove > spaceBelow;
+    const left = Math.min(
+      Math.max(rect.right - WIDTH, 8),
+      window.innerWidth - WIDTH - 8,
+    );
+    setLufsTgtPopStyle({
+      position: 'fixed',
+      left,
+      width: WIDTH,
+      ...(useAbove
+        ? { bottom: window.innerHeight - rect.top + MARGIN }
+        : { top: rect.bottom + MARGIN }),
+      maxHeight: Math.min(MAX_H, useAbove ? spaceAbove : spaceBelow),
+      zIndex: 99998,
+    });
+  };
+
+  useLayoutEffect(() => {
+    if (!lufsTgtOpen) return;
+    updateLufsTgtPopStyle();
+  }, [lufsTgtOpen]);
+
+  useEffect(() => {
+    if (!lufsTgtOpen) return;
+    const onResize = () => updateLufsTgtPopStyle();
+    window.addEventListener('resize', onResize);
+    window.addEventListener('scroll', onResize, true);
+    return () => {
+      window.removeEventListener('resize', onResize);
+      window.removeEventListener('scroll', onResize, true);
+    };
+  }, [lufsTgtOpen]);
+
+  useEffect(() => {
+    if (!expandReplayGain) setLufsTgtOpen(false);
+  }, [expandReplayGain]);
+
   // Tracks which queue index is being psy-dragged for opacity visual feedback
   const psyDragFromIdxRef = useRef<number | null>(null);
 
@@ -534,8 +605,15 @@ function QueuePanelHostOrSolo() {
             const rgParts = formatQueueReplayGainParts(currentTrack, t);
             const baseLine = baseParts.join(' · ');
             const rgLine = rgParts.join(' · ');
+            const isLoudnessActive = normalizationEngine === 'loudness' || normalizationEngineLive === 'loudness';
+            const liveGainLabel = normalizationNowDb != null
+              ? `${normalizationNowDb >= 0 ? '+' : ''}${normalizationNowDb.toFixed(2)} dB`
+              : '—';
+            const tgtNum = normalizationTargetLufs ?? authLoudnessTargetLufs;
+            const targetLabel = `${tgtNum} LUFS`;
             if (!baseLine && !rgLine && !playbackSource) return null;
-            const showRgLine = expandReplayGain && !!rgLine;
+            const showRgLine = !isLoudnessActive && expandReplayGain && !!rgLine;
+            const showLufsLine = isLoudnessActive && expandReplayGain;
             return (
               <div className={`queue-current-tech${showRgLine ? ' queue-current-tech--two-line' : ''}`}>
                 <div className="queue-current-tech-stack">
@@ -558,7 +636,7 @@ function QueuePanelHostOrSolo() {
                       </span>
                     )}
                     {baseLine && <span className="queue-current-tech-main">{baseLine}</span>}
-                    {rgLine && (
+                    {!isLoudnessActive && rgLine && (
                       <button
                         type="button"
                         className={`queue-current-tech-rg-badge${showRgLine ? ' queue-current-tech-rg-badge--open' : ''}`}
@@ -571,6 +649,19 @@ function QueuePanelHostOrSolo() {
                         <ChevronDown size={9} strokeWidth={2.5} />
                       </button>
                     )}
+                    {isLoudnessActive && (
+                      <button
+                        type="button"
+                        className={`queue-current-tech-rg-badge${showLufsLine ? ' queue-current-tech-rg-badge--open' : ''}`}
+                        data-tooltip={`LUFS · ${liveGainLabel} · TGT · ${targetLabel}`}
+                        aria-expanded={showLufsLine}
+                        aria-label="LUFS"
+                        onClick={() => setExpandReplayGain(!expandReplayGain)}
+                      >
+                        LUFS
+                        <ChevronDown size={9} strokeWidth={2.5} />
+                      </button>
+                    )}
                   </div>
                   {showRgLine && (
                     <span className="queue-current-tech-rg">
@@ -578,6 +669,90 @@ function QueuePanelHostOrSolo() {
                       {' · '}{rgLine}
                     </span>
                   )}
+                  {showLufsLine && (
+                    <span className="queue-current-tech-rg">
+                      <span className="queue-current-tech-rg-label">Loudness</span>
+                      {' · '}
+                      <button
+                        type="button"
+                        className="queue-current-tech-metric"
+                        onClick={e => {
+                          e.stopPropagation();
+                          setLufsTgtOpen(false);
+                          void reanalyzeLoudnessForTrack(currentTrack.id);
+                        }}
+                        data-tooltip="Clear cached loudness and re-analyze this track"
+                      >
+                        {liveGainLabel}
+                      </button>
+                      {' · '}
+                      <span className="queue-current-tech-rg-label">TGT</span>
+                      {' · '}
+                      <button
+                        type="button"
+                        ref={lufsTgtBtnRef}
+                        className="queue-current-tech-metric"
+                        onClick={e => {
+                          e.stopPropagation();
+                          setLufsTgtOpen(v => !v);
+                        }}
+                        data-tooltip="Change target integrated loudness"
+                        aria-haspopup="listbox"
+                        aria-expanded={lufsTgtOpen}
+                      >
+                        {targetLabel}
+                      </button>
+                      {lufsTgtOpen &&
+                        createPortal(
+                          <div
+                            ref={lufsTgtMenuRef}
+                            className="queue-lufs-tgt-menu"
+                            style={{
+                              ...lufsTgtPopStyle,
+                              background: 'var(--bg-card)',
+                              border: '1px solid var(--border, rgba(255,255,255,0.12))',
+                              borderRadius: 8,
+                              boxShadow: '0 6px 24px rgba(0,0,0,0.35)',
+                              padding: 6,
+                              overflow: 'auto',
+                            }}
+                            role="listbox"
+                            aria-label="LUFS target"
+                            onClick={e => e.stopPropagation()}
+                          >
+                            {([-10, -12, -14, -16] as const).map((v) => (
+                              <button
+                                key={v}
+                                type="button"
+                                onClick={e => {
+                                  e.stopPropagation();
+                                  if (v !== authLoudnessTargetLufs) {
+                                    setLoudnessTargetLufs(v);
+                                    void reanalyzeLoudnessForTrack(currentTrack.id);
+                                  }
+                                  setLufsTgtOpen(false);
+                                }}
+                                style={{
+                                  display: 'block',
+                                  width: '100%',
+                                  textAlign: 'left',
+                                  padding: '6px 8px',
+                                  borderRadius: 6,
+                                  border: 'none',
+                                  background: v === authLoudnessTargetLufs ? 'color-mix(in srgb, var(--accent) 18%, transparent)' : 'transparent',
+                                  color: 'var(--text-primary)',
+                                  cursor: 'pointer',
+                                  font: 'inherit',
+                                }}
+                              >
+                                {v} LUFS
+                              </button>
+                            ))}
+                          </div>,
+                          document.body,
+                        )}
+                    </span>
+                  )}
                 </div>
               </div>
             );

src/components/WaveformSeek.tsx

@@ -8,6 +8,8 @@ function fmt(s: number): string {
 
 const BAR_COUNT = 500;
 const SEG_COUNT = 60;
+const FLAT_WAVE_NORM = 0.06;
+const WAVE_MORPH_MS = 1000;
 
 // ── animation state ───────────────────────────────────────────────────────────
 
@@ -96,6 +98,40 @@ export function makeHeights(trackId: string): Float32Array {
 
 // ── draw functions ────────────────────────────────────────────────────────────
 
+function makeFlatWaveHeights(): Float32Array {
+  const h = new Float32Array(BAR_COUNT);
+  h.fill(FLAT_WAVE_NORM);
+  return h;
+}
+
+function easeOutCubic(t: number): number {
+  const x = Math.max(0, Math.min(1, t));
+  return 1 - Math.pow(1 - x, 3);
+}
+
+function binsToHeights(src: number[]): Float32Array {
+  const h = new Float32Array(BAR_COUNT);
+  for (let i = 0; i < BAR_COUNT; i++) {
+    const idx = Math.min(src.length - 1, Math.floor((i / BAR_COUNT) * src.length));
+    const v = src[idx];
+    h[i] = Math.max(0.08, Math.min(1, (Number(v) / 255)));
+  }
+  return h;
+}
+
+function heightsNearlyEqual(a: Float32Array, b: Float32Array, eps: number): boolean {
+  if (a.length !== b.length) return false;
+  for (let i = 0; i < a.length; i++) {
+    if (Math.abs(a[i] - b[i]) > eps) return false;
+  }
+  return true;
+}
+
+function waveformBarThickness(logicalH: number, norm: number): number {
+  const safeNorm = Math.max(FLAT_WAVE_NORM, norm);
+  return Math.max(1, safeNorm * logicalH);
+}
+
 function drawWaveform(
   canvas: HTMLCanvasElement,
   heights: Float32Array | null,
@@ -108,9 +144,38 @@ function drawWaveform(
   const { played, buffered: buffCol, unplayed } = getColors();
 
   if (!heights) {
-    ctx.globalAlpha = 0.3;
+    // No waveform data yet: flat rail like `drawLineDot`, but do not return early
+    // before played/buffered — otherwise there is no visible playhead.
+    const cy = h / 2;
+    const lh = 2;
+    const dotR = 5;
+    ctx.globalAlpha = 0.35;
     ctx.fillStyle = unplayed;
-    ctx.fillRect(0, (h - 2) / 2, w, 2);
+    ctx.fillRect(0, cy - lh / 2, w, lh);
+    if (buffered > 0) {
+      ctx.globalAlpha = 0.55;
+      ctx.fillStyle = buffCol;
+      ctx.fillRect(0, cy - lh / 2, Math.min(1, buffered) * w, lh);
+    }
+    if (progress > 0) {
+      ctx.globalAlpha = 1;
+      ctx.fillStyle = played;
+      ctx.shadowColor = played;
+      ctx.shadowBlur = 5;
+      ctx.fillRect(0, cy - lh / 2, Math.min(1, progress) * w, lh);
+      ctx.shadowBlur = 0;
+    }
+    ctx.globalAlpha = 1;
+    if (w > 0) {
+      const dx = Math.max(dotR, Math.min(w - dotR, Math.min(1, progress) * w));
+      ctx.shadowColor = played;
+      ctx.shadowBlur = 7;
+      ctx.beginPath();
+      ctx.arc(dx, cy, dotR, 0, Math.PI * 2);
+      ctx.fillStyle = played;
+      ctx.fill();
+      ctx.shadowBlur = 0;
+    }
     ctx.globalAlpha = 1;
     return;
   }
@@ -122,7 +187,7 @@ function drawWaveform(
   ctx.fillStyle = unplayed;
   for (let i = 0; i < BAR_COUNT; i++) {
     if (i / BAR_COUNT < buffered) continue;
-    const bh = Math.max(1, heights[i] * h);
+    const bh = waveformBarThickness(h, heights[i]);
     const x = x1Of(i);
     ctx.fillRect(x, (h - bh) / 2, x2Of(i) - x, bh);
   }
@@ -132,7 +197,7 @@ function drawWaveform(
   for (let i = 0; i < BAR_COUNT; i++) {
     const frac = i / BAR_COUNT;
     if (frac < progress || frac >= buffered) continue;
-    const bh = Math.max(1, heights[i] * h);
+    const bh = waveformBarThickness(h, heights[i]);
     const x = x1Of(i);
     ctx.fillRect(x, (h - bh) / 2, x2Of(i) - x, bh);
   }
@@ -140,29 +205,14 @@ function drawWaveform(
   if (progress > 0) {
     ctx.globalAlpha = 1;
     ctx.fillStyle = played;
-    ctx.shadowColor = played;
-    ctx.shadowBlur = 5;
     for (let i = 0; i < BAR_COUNT; i++) {
       if (i / BAR_COUNT >= progress) break;
-      const bh = Math.max(1, heights[i] * h);
+      const bh = waveformBarThickness(h, heights[i]);
       const x = x1Of(i);
       ctx.fillRect(x, (h - bh) / 2, x2Of(i) - x, bh);
     }
-    ctx.shadowBlur = 0;
   }
   ctx.globalAlpha = 1;
-
-  // Fade both edges to transparent using destination-in gradient mask
-  const fadeW = Math.min(22, w * 0.07);
-  const mask = ctx.createLinearGradient(0, 0, w, 0);
-  mask.addColorStop(0, 'transparent');
-  mask.addColorStop(fadeW / w, 'black');
-  mask.addColorStop(1 - fadeW / w, 'black');
-  mask.addColorStop(1, 'transparent');
-  ctx.globalCompositeOperation = 'destination-in';
-  ctx.fillStyle = mask;
-  ctx.fillRect(0, 0, w, h);
-  ctx.globalCompositeOperation = 'source-over';
 }
 
 function drawLineDot(canvas: HTMLCanvasElement, progress: number, buffered: number) {
@@ -832,6 +882,7 @@ export default function WaveformSeek({ trackId }: Props) {
   const [hoverPct, setHoverPct] = useState<number | null>(null);
 
   const seek         = usePlayerStore(s => s.seek);
+  const waveformBins = usePlayerStore(s => s.waveformBins);
   const duration     = usePlayerStore(s => s.currentTrack?.duration ?? 0);
   const seekbarStyle = useAuthStore(s => s.seekbarStyle);
 
@@ -845,8 +896,70 @@ export default function WaveformSeek({ trackId }: Props) {
       heightsRef.current = null;
       return;
     }
-    heightsRef.current = makeHeights(trackId);
+    if (waveformBins && waveformBins.length > 0) {
-  }, [trackId]);
+      const h = binsToHeights(waveformBins);
+      const prev = heightsRef.current;
+      if (!prev || prev.length !== BAR_COUNT) {
+        heightsRef.current = h;
+        return;
+      }
+      if (heightsNearlyEqual(prev, h, 0.02)) {
+        heightsRef.current = h;
+        return;
+      }
+      const from = new Float32Array(prev);
+      const to = h;
+      const startedAt = performance.now();
+      let raf = 0;
+      const step = (now: number) => {
+        const p = easeOutCubic((now - startedAt) / WAVE_MORPH_MS);
+        const next = new Float32Array(BAR_COUNT);
+        for (let i = 0; i < BAR_COUNT; i++) {
+          next[i] = from[i] + (to[i] - from[i]) * p;
+        }
+        heightsRef.current = next;
+        if (!ANIMATED_STYLES.has(styleRef.current)) {
+          const canvas = canvasRef.current;
+          if (canvas) drawSeekbar(canvas, styleRef.current, next, progressRef.current, bufferedRef.current, animStateRef.current);
+        }
+        if (p < 1) raf = requestAnimationFrame(step);
+      };
+      raf = requestAnimationFrame(step);
+      return () => cancelAnimationFrame(raf);
+    }
+    if (heightsRef.current?.length === BAR_COUNT) {
+      const current = heightsRef.current;
+      let isAlreadyFlat = true;
+      for (let i = 0; i < BAR_COUNT; i++) {
+        if (Math.abs(current[i] - FLAT_WAVE_NORM) > 0.0001) {
+          isAlreadyFlat = false;
+          break;
+        }
+      }
+      if (isAlreadyFlat) return;
+      const from = new Float32Array(current);
+      const to = makeFlatWaveHeights();
+      const startedAt = performance.now();
+      let raf = 0;
+      const step = (now: number) => {
+        const p = easeOutCubic((now - startedAt) / WAVE_MORPH_MS);
+        const next = new Float32Array(BAR_COUNT);
+        for (let i = 0; i < BAR_COUNT; i++) {
+          next[i] = from[i] + (to[i] - from[i]) * p;
+        }
+        heightsRef.current = next;
+        if (!ANIMATED_STYLES.has(styleRef.current)) {
+          const canvas = canvasRef.current;
+          if (canvas) drawSeekbar(canvas, styleRef.current, next, progressRef.current, bufferedRef.current, animStateRef.current);
+        }
+        if (p < 1) raf = requestAnimationFrame(step);
+      };
+      raf = requestAnimationFrame(step);
+      return () => cancelAnimationFrame(raf);
+    }
+    // No analysis bins yet: render 500 flat bars immediately.
+    heightsRef.current = makeFlatWaveHeights();
+  }, [trackId, waveformBins]);
 
   // Imperative subscription — no React re-renders from progress changes.
   // Static styles draw here; animated styles only update refs.
@@ -874,12 +987,17 @@ export default function WaveformSeek({ trackId }: Props) {
     });
   }, []);
 
-  // Initial draw for static styles when style or track changes.
+  // Initial draw for static styles when style, track, or waveform payload changes.
   useEffect(() => {
     if (ANIMATED_STYLES.has(seekbarStyle)) return;
     const canvas = canvasRef.current;
     if (canvas) drawSeekbar(canvas, seekbarStyle, heightsRef.current, progressRef.current, bufferedRef.current);
-  }, [seekbarStyle, trackId]);
+  }, [
+    seekbarStyle,
+    trackId,
+    waveformBins,
+    duration,
+  ]);
 
   // rAF loop — animated styles only.
   useEffect(() => {

src/locales/de.ts

@@ -847,6 +847,12 @@ export const deTranslation = {
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pre-Gain (getaggte Dateien)',
     replayGainFallback: 'Fallback (ohne Tags / Radio)',
+    normalization: 'Normalisierung',
+    loudnessTargetLufs: 'Ziel-LUFS',
+    loudnessPreAnalysisAttenuation: 'Dämpfung vor Messung (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Zusätzliche Dämpfung, bis die Loudness des Titels gespeichert ist. Beim Streamen folgen nur grobe Schätzungen, keine volle Messung. 0 dB = aus; negativer = leiser.',
+    loudnessPreAnalysisAttenuationReset: 'Standard',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Überblendung zwischen Tracks',
     crossfadeSecs: '{{n}} s',

src/locales/en.ts

@@ -656,9 +656,12 @@ export const enTranslation = {
     hotCacheTrackCount: 'Tracks in cache:',
     cacheMaxLabel: 'Max. size',
     cacheClearBtn: 'Clear Cache',
+    waveformCacheClearBtn: 'Clear waveform cache',
     cacheClearWarning: 'This will also remove all offline albums from the library.',
     cacheClearConfirm: 'Clear Everything',
     cacheClearCancel: 'Cancel',
+    waveformCacheCleared: 'Waveform cache cleared ({{count}} rows).',
+    waveformCacheClearFailed: 'Failed to clear waveform cache.',
     offlineDirTitle: 'Offline Library (In-App)',
     offlineDirDesc: 'Storage location for tracks you make available offline within Psysonic.',
     offlineDirDefault: 'Default (App Data)',
@@ -850,6 +853,12 @@ export const enTranslation = {
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pre-Gain (tagged files)',
     replayGainFallback: 'Fallback (untagged / radio)',
+    normalization: 'Normalization',
+    loudnessTargetLufs: 'Target LUFS',
+    loudnessPreAnalysisAttenuation: 'Trim before measurement (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Extra quieting until loudness for this track is saved. Streaming then uses rough guesses, not a full measurement. 0 dB = off; lower = quieter.',
+    loudnessPreAnalysisAttenuationReset: 'Reset to default',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Fade between tracks',
     crossfadeSecs: '{{n}} s',

src/locales/es.ts

@@ -840,6 +840,12 @@ export const esTranslation = {
     replayGainAlbum: 'Álbum',
     replayGainPreGain: 'Pre-Ganancia (archivos etiquetados)',
     replayGainFallback: 'Respaldo (sin etiquetar / radio)',
+    normalization: 'Normalización',
+    loudnessTargetLufs: 'LUFS objetivo',
+    loudnessPreAnalysisAttenuation: 'Atenuación antes de medir (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Atenúa hasta que la loudness del tema esté guardada. En streaming luego solo hay estimaciones aproximadas. 0 dB = ninguna; más negativo = más bajo.',
+    loudnessPreAnalysisAttenuationReset: 'Predeterminado',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Transición entre pistas',
     crossfadeSecs: '{{n}} s',

src/locales/fr.ts

@@ -835,6 +835,12 @@ export const frTranslation = {
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pré-Gain (fichiers taggés)',
     replayGainFallback: 'Repli (sans tags / radio)',
+    normalization: 'Normalisation',
+    loudnessTargetLufs: 'LUFS cible',
+    loudnessPreAnalysisAttenuation: 'Atténuation avant mesure (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Réduit le volume tant que la loudness du morceau n’est pas enregistrée. En streaming, des estimations grossières suivent, pas une mesure complète. 0 dB = rien ; plus négatif = plus discret.',
+    loudnessPreAnalysisAttenuationReset: 'Valeur par défaut',
     crossfade: 'Fondu enchaîné',
     crossfadeDesc: 'Fondu entre les pistes',
     crossfadeSecs: '{{n}} s',

src/locales/nb.ts

@@ -834,6 +834,12 @@ export const nbTranslation = {
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pre-Gain (taggede filer)',
     replayGainFallback: 'Reserveverdi (uten tagger / radio)',
+    normalization: 'Normalisering',
+    loudnessTargetLufs: 'Mål-LUFS',
+    loudnessPreAnalysisAttenuation: 'Demping før måling (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Ekstra demping til loudness for sporet er lagret. Streaming bruker deretter grove anslag, ikke full måling. 0 dB = av; lavere = roligere.',
+    loudnessPreAnalysisAttenuationReset: 'Standard',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Tone mellom spor',
     crossfadeSecs: '{{n}}s',

src/locales/nl.ts

@@ -834,6 +834,12 @@ export const nlTranslation = {
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pre-Gain (getagde bestanden)',
     replayGainFallback: 'Terugval (zonder tags / radio)',
+    normalization: 'Normalisatie',
+    loudnessTargetLufs: 'Doel-LUFS',
+    loudnessPreAnalysisAttenuation: 'Demping vóór meting (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Extra zachter tot de loudness van het nummer is opgeslagen. Streamen gebruikt daarna grove schattingen, geen volledige meting. 0 dB = uit; negatiever = zachter.',
+    loudnessPreAnalysisAttenuationReset: 'Standaard',
     crossfade: 'Overgang',
     crossfadeDesc: 'Fade tussen nummers',
     crossfadeSecs: '{{n}} s',

src/locales/ru.ts

@@ -677,9 +677,12 @@ export const ruTranslation = {
     hotCacheTrackCount: 'Треков в кэше:',
     cacheMaxLabel: 'Лимит',
     cacheClearBtn: 'Очистить кэш',
+    waveformCacheClearBtn: 'Очистить кэш waveform',
     cacheClearWarning: 'Будут удалены и все офлайн-альбомы.',
     cacheClearConfirm: 'Очистить всё',
     cacheClearCancel: 'Отмена',
+    waveformCacheCleared: 'Кэш waveform очищен ({{count}} строк).',
+    waveformCacheClearFailed: 'Не удалось очистить кэш waveform.',
     offlineDirTitle: 'Офлайн-библиотека (в приложении)',
     offlineDirDesc: 'Папка для треков, сохранённых для офлайн-прослушивания.',
     offlineDirDefault: 'По умолчанию (данные приложения)',
@@ -883,6 +886,12 @@ export const ruTranslation = {
     replayGainAlbum: 'По альбому',
     replayGainPreGain: 'Предусиление (файлы с тегами)',
     replayGainFallback: 'Резерв (без тегов / радио)',
+    normalization: 'Нормализация',
+    loudnessTargetLufs: 'Целевой LUFS',
+    loudnessPreAnalysisAttenuation: 'Ослабление до измерения (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Насколько приглушить звук, пока для трека нет сохранённого измерения громкости. При стриме дальше идут лишь грубые оценки, не полный LUFS. 0 dB — без дополнительного приглушения; ниже — тише.',
+    loudnessPreAnalysisAttenuationReset: 'По умолчанию',
     crossfade: 'Кроссфейд',
     crossfadeDesc: 'Плавный переход между треками',
     crossfadeSecs: '{{n}} с',

src/locales/zh.ts

@@ -829,6 +829,12 @@ export const zhTranslation = {
     replayGainAlbum: '专辑',
     replayGainPreGain: '预增益（有标签文件）',
     replayGainFallback: '回退增益（无标签 / 收音机）',
+    normalization: '响度归一化',
+    loudnessTargetLufs: '目标 LUFS',
+    loudnessPreAnalysisAttenuation: '测量前衰减 (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      '在曲目响度数据保存前的额外压低。流式阶段之后只是粗略估计，不是完整测量。0 dB 为不压低；更负则更安静。',
+    loudnessPreAnalysisAttenuationReset: '恢复默认',
     crossfade: '交叉淡入淡出',
     crossfadeDesc: '曲目间淡入淡出',
     crossfadeSecs: '{{n}} 秒',

src/main.tsx

@@ -30,6 +30,22 @@ try {
   // Ignore in non-Tauri runtimes.
 }
 
+// Zustand rehydrate runs after first paint; AppShell's useEffect can miss the
+// user's persisted `loggingMode` until then — but waveform/audio may already
+// run. Push persisted mode to Rust before React mounts (matches `psysonic-auth`).
+try {
+  const raw = localStorage.getItem('psysonic-auth');
+  if (raw) {
+    const parsed = JSON.parse(raw) as { state?: { loggingMode?: string } };
+    const mode = parsed.state?.loggingMode;
+    if (mode === 'off' || mode === 'normal' || mode === 'debug') {
+      void invoke('set_logging_mode', { mode });
+    }
+  }
+} catch {
+  // Ignore parse / non-Tauri.
+}
+
 ReactDOM.createRoot(document.getElementById('root')!).render(
   <StrictMode>
     <App />

src/pages/Settings.tsx

@@ -17,6 +17,7 @@ import { open as openUrl } from '@tauri-apps/plugin-shell';
 import { getImageCacheSize, clearImageCache } from '../utils/imageCache';
 import { useOfflineStore } from '../store/offlineStore';
 import { useHotCacheStore } from '../store/hotCacheStore';
+import { usePlayerStore } from '../store/playerStore';
 import { lastfmGetToken, lastfmAuthUrl, lastfmGetSession, lastfmGetUserInfo, LastfmUserInfo } from '../api/lastfm';
 import LastfmIcon from '../components/LastfmIcon';
 import CustomSelect from '../components/CustomSelect';
@@ -25,7 +26,17 @@ import { AboutPsysonicBrandHeader } from '../components/AboutPsysonicLol';
 import { useLuckyMixAvailable } from '../hooks/useLuckyMixAvailable';
 import ThemePicker, { THEME_GROUPS } from '../components/ThemePicker';
 import { useShallow } from 'zustand/react/shallow';
-import { useAuthStore, ServerProfile, MIX_MIN_RATING_FILTER_MAX_STARS, type SeekbarStyle, type LyricsSourceId, type LyricsSourceConfig, type LoggingMode } from '../store/authStore';
+import {
+  useAuthStore,
+  DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB,
+  ServerProfile,
+  MIX_MIN_RATING_FILTER_MAX_STARS,
+  type SeekbarStyle,
+  type LyricsSourceId,
+  type LyricsSourceConfig,
+  type LoggingMode,
+  type LoudnessLufsPreset,
+} from '../store/authStore';
 import { SeekbarPreview } from '../components/WaveformSeek';
 import { IS_LINUX, IS_MACOS, IS_WINDOWS } from '../utils/platform';
 import { useThemeStore } from '../store/themeStore';
@@ -64,6 +75,29 @@ const AUDIOBOOK_GENRES_DISPLAY = ['Hörbuch', 'Hoerbuch', 'Hörspiel', 'Hoerspie
 
 const AUDIOMUSE_NV_PLUGIN_URL = 'https://github.com/NeptuneHub/AudioMuse-AI-NV-plugin';
 
+const LOUDNESS_LUFS_BUTTON_ORDER: LoudnessLufsPreset[] = [-10, -12, -14, -16];
+
+function LoudnessLufsButtonGroup(props: {
+  value: LoudnessLufsPreset;
+  onSelect: (v: LoudnessLufsPreset) => void;
+}) {
+  return (
+    <div style={{ display: 'flex', alignItems: 'center', gap: '0.35rem', flexWrap: 'wrap' }}>
+      {LOUDNESS_LUFS_BUTTON_ORDER.map(v => (
+        <button
+          key={v}
+          type="button"
+          className={`btn ${props.value === v ? 'btn-primary' : 'btn-ghost'}`}
+          style={{ fontSize: 12, padding: '3px 12px' }}
+          onClick={() => props.onSelect(v)}
+        >
+          {v}
+        </button>
+      ))}
+    </div>
+  );
+}
+
 const CONTRIBUTORS = [
   {
     github: 'jiezhuo',
@@ -1788,6 +1822,26 @@ export default function Settings() {
     setClearing(false);
   }, [clearAllOffline, serverId]);
 
+  const handleClearWaveformCache = useCallback(async () => {
+    setClearing(true);
+    try {
+      const deleted = await invoke<number>('analysis_delete_all_waveforms');
+      usePlayerStore.setState({
+        waveformBins: null,
+      });
+      showToast(
+        t('settings.waveformCacheCleared', { count: deleted }),
+        3500,
+        'success',
+      );
+    } catch (e) {
+      console.error(e);
+      showToast(t('settings.waveformCacheClearFailed'), 4500, 'error');
+    } finally {
+      setClearing(false);
+    }
+  }, [t]);
+
   const startLastfmConnect = useCallback(async () => {
     setLfmError(null);
     let token: string;
@@ -2217,19 +2271,89 @@ export default function Settings() {
             icon={<Music2 size={16} />}
           >
             <div className="settings-card">
-              {/* Replay Gain */}
+              {/* Normalization */}
               <div className="settings-toggle-row">
-                <div>
+                <div style={{ fontWeight: 500 }}>{t('settings.normalization', { defaultValue: 'Normalization' })}</div>
-                  <div style={{ fontWeight: 500 }}>{t('settings.replayGain')}</div>
+                <div style={{ display: 'flex', alignItems: 'center', gap: '0.5rem' }}>
-                  <div style={{ fontSize: 12, color: 'var(--text-muted)' }}>{t('settings.replayGainDesc')}</div>
+                  <button
+                    className={`btn ${auth.normalizationEngine === 'off' ? 'btn-primary' : 'btn-ghost'}`}
+                    style={{ fontSize: 12, padding: '3px 10px' }}
+                    onClick={() => {
+                      auth.setReplayGainEnabled(false);
+                      auth.setNormalizationEngine('off');
+                    }}
+                  >
+                    Off
+                  </button>
+                  <button
+                    className={`btn ${auth.normalizationEngine === 'replaygain' ? 'btn-primary' : 'btn-ghost'}`}
+                    style={{ fontSize: 12, padding: '3px 10px' }}
+                    onClick={() => {
+                      auth.setReplayGainEnabled(true);
+                      auth.setNormalizationEngine('replaygain');
+                    }}
+                  >
+                    RG
+                  </button>
+                  <button
+                    className={`btn ${auth.normalizationEngine === 'loudness' ? 'btn-primary' : 'btn-ghost'}`}
+                    style={{ fontSize: 12, padding: '3px 10px' }}
+                    onClick={() => {
+                      auth.setReplayGainEnabled(false);
+                      if (auth.normalizationEngine !== 'loudness') auth.setLoudnessTargetLufs(-12);
+                      auth.setNormalizationEngine('loudness');
+                    }}
+                  >
+                    LUFS
+                  </button>
                 </div>
-                <label className="toggle-switch" aria-label={t('settings.replayGain')}>
-                  <input type="checkbox" checked={auth.replayGainEnabled} onChange={e => auth.setReplayGainEnabled(e.target.checked)} id="replay-gain-toggle" />
-                  <span className="toggle-track" />
-                </label>
               </div>
-              {auth.replayGainEnabled && (
+              {auth.normalizationEngine === 'loudness' && (
+                <div style={{ paddingLeft: '1rem', marginTop: '0.5rem', display: 'flex', flexDirection: 'column', gap: '0.55rem' }}>
+                  <div style={{ display: 'flex', flexWrap: 'wrap', alignItems: 'center', gap: '0.75rem' }}>
+                    <span style={{ fontSize: 13, color: 'var(--text-secondary)', minWidth: 140 }}>
+                      {t('settings.loudnessTargetLufs')}
+                    </span>
+                    <LoudnessLufsButtonGroup value={auth.loudnessTargetLufs} onSelect={auth.setLoudnessTargetLufs} />
+                  </div>
+                  <div style={{ display: 'flex', alignItems: 'center', gap: '0.75rem', flexWrap: 'wrap' }}>
+                    <span style={{ fontSize: 13, color: 'var(--text-secondary)', minWidth: 140 }}>
+                      {t('settings.loudnessPreAnalysisAttenuation')}
+                    </span>
+                    <input
+                      type="range"
+                      min={-24}
+                      max={0}
+                      step={0.5}
+                      value={auth.loudnessPreAnalysisAttenuationDb}
+                      onChange={e => auth.setLoudnessPreAnalysisAttenuationDb(Number(e.target.value))}
+                      style={{ flex: 1, minWidth: 80, maxWidth: 200 }}
+                    />
+                    <span style={{ fontSize: 12, color: 'var(--text-muted)', minWidth: 44, textAlign: 'right' }}>
+                      {auth.loudnessPreAnalysisAttenuationDb} dB
+                    </span>
+                    <button
+                      type="button"
+                      className="icon-btn"
+                      style={{ flexShrink: 0 }}
+                      disabled={
+                        auth.loudnessPreAnalysisAttenuationDb === DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB
+                      }
+                      onClick={() => auth.resetLoudnessPreAnalysisAttenuationDbDefault()}
+                      data-tooltip={t('settings.loudnessPreAnalysisAttenuationReset')}
+                      aria-label={t('settings.loudnessPreAnalysisAttenuationReset')}
+                    >
+                      <RotateCcw size={15} />
+                    </button>
+                  </div>
+                  <div style={{ fontSize: 11, color: 'var(--text-muted)', lineHeight: 1.35, maxWidth: 520 }}>
+                    {t('settings.loudnessPreAnalysisAttenuationDesc')}
+                  </div>
+                </div>
+              )}
+              {auth.normalizationEngine !== 'off' && (
                 <div style={{ paddingLeft: '1rem', marginTop: '0.5rem', display: 'flex', flexDirection: 'column', gap: '0.4rem' }}>
+                  {auth.normalizationEngine === 'replaygain' && (
                   <div style={{ display: 'flex', alignItems: 'center', gap: '0.75rem', flexWrap: 'wrap' }}>
                     <span style={{ fontSize: 13, color: 'var(--text-secondary)' }}>{t('settings.replayGainMode')}:</span>
                     <button
@@ -2254,14 +2378,15 @@ export default function Settings() {
                       {t('settings.replayGainAlbum')}
                     </button>
                   </div>
-                  {auth.replayGainMode === 'auto' && (
+                  )}
+                  {auth.normalizationEngine === 'replaygain' && auth.replayGainMode === 'auto' && (
                     <div style={{ fontSize: 12, color: 'var(--text-muted)' }}>
                       {t('settings.replayGainAutoDesc')}
                     </div>
                   )}
                 </div>
               )}
-              {auth.replayGainEnabled && (
+              {auth.normalizationEngine === 'replaygain' && (
                 <div style={{ paddingLeft: '1rem', marginTop: '0.75rem', display: 'flex', flexDirection: 'column', gap: '0.6rem' }}>
                   <div style={{ display: 'flex', alignItems: 'center', gap: '0.75rem', flexWrap: 'wrap' }}>
                     <span style={{ fontSize: 13, color: 'var(--text-secondary)', minWidth: 100 }}>
@@ -2964,6 +3089,16 @@ export default function Settings() {
                   <Trash2 size={14} /> {t('settings.cacheClearBtn')}
                 </button>
               )}
+              <div style={{ marginTop: 8 }}>
+                <button
+                  className="btn btn-ghost"
+                  style={{ fontSize: 13 }}
+                  onClick={handleClearWaveformCache}
+                  disabled={clearing}
+                >
+                  <Trash2 size={14} /> {t('settings.waveformCacheClearBtn')}
+                </button>
+              </div>
             </div>
           </SettingsSubSection>
 

src/store/analysisSync.ts

@@ -0,0 +1,29 @@
+export type AnalysisStorageChangedReason =
+  | 'offline-delete'
+  | 'hotcache-delete'
+  | 'hotcache-purge';
+
+export type AnalysisStorageChangedDetail = {
+  trackId?: string | null;
+  reason: AnalysisStorageChangedReason;
+};
+
+const EVENT_NAME = 'psysonic:analysis-storage-changed';
+
+export function emitAnalysisStorageChanged(detail: AnalysisStorageChangedDetail): void {
+  if (typeof window === 'undefined') return;
+  window.dispatchEvent(new CustomEvent<AnalysisStorageChangedDetail>(EVENT_NAME, { detail }));
+}
+
+export function onAnalysisStorageChanged(
+  listener: (detail: AnalysisStorageChangedDetail) => void,
+): () => void {
+  if (typeof window === 'undefined') return () => {};
+  const wrapped = (evt: Event) => {
+    const ce = evt as CustomEvent<AnalysisStorageChangedDetail>;
+    if (!ce?.detail) return;
+    listener(ce.detail);
+  };
+  window.addEventListener(EVENT_NAME, wrapped as EventListener);
+  return () => window.removeEventListener(EVENT_NAME, wrapped as EventListener);
+}

src/store/authStore.ts

@@ -20,6 +20,28 @@ export interface ServerProfile {
 
 export type SeekbarStyle = 'waveform' | 'linedot' | 'bar' | 'thick' | 'segmented' | 'neon' | 'pulsewave' | 'particletrail' | 'liquidfill' | 'retrotape';
 export type LoggingMode = 'off' | 'normal' | 'debug';
+export type NormalizationEngine = 'off' | 'replaygain' | 'loudness';
+
+/** Integrated-loudness target presets (Settings + analysis). */
+export type LoudnessLufsPreset = -16 | -14 | -12 | -10;
+
+const LOUDNESS_LUFS_PRESETS: LoudnessLufsPreset[] = [-16, -14, -12, -10];
+
+/** Settings default + Rust engine cold default until `audio_set_normalization` runs. */
+export const DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB = -4.5;
+
+function sanitizeLoudnessLufsPreset(v: unknown, fallback: LoudnessLufsPreset): LoudnessLufsPreset {
+  return (LOUDNESS_LUFS_PRESETS as readonly number[]).includes(v as number)
+    ? (v as LoudnessLufsPreset)
+    : fallback;
+}
+
+function clampLoudnessPreAnalysisAttenuationDb(v: unknown): number {
+  const n = typeof v === 'number' ? v : Number(v);
+  if (!Number.isFinite(n)) return DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB;
+  const stepped = Math.round(n * 2) / 2;
+  return Math.max(-24, Math.min(0, stepped));
+}
 
 export type LyricsSourceId = 'server' | 'lrclib' | 'netease';
 export interface LyricsSourceConfig { id: LyricsSourceId; enabled: boolean; }
@@ -49,6 +71,10 @@ interface AuthState {
   excludeAudiobooks: boolean;
   customGenreBlacklist: string[];
   replayGainEnabled: boolean;
+  normalizationEngine: NormalizationEngine;
+  loudnessTargetLufs: LoudnessLufsPreset;
+  /** dB: extra quieting until loudness is saved; also seeds streaming rough-guess ramp. */
+  loudnessPreAnalysisAttenuationDb: number;
   replayGainMode: 'track' | 'album' | 'auto';
   replayGainPreGainDb: number;   // added to RG gain for tagged files (0…+6 dB)
   replayGainFallbackDb: number;  // gain for untagged files / radio (-6…0 dB)
@@ -208,6 +234,10 @@ interface AuthState {
   setExcludeAudiobooks: (v: boolean) => void;
   setCustomGenreBlacklist: (v: string[]) => void;
   setReplayGainEnabled: (v: boolean) => void;
+  setNormalizationEngine: (v: NormalizationEngine) => void;
+  setLoudnessTargetLufs: (v: LoudnessLufsPreset) => void;
+  setLoudnessPreAnalysisAttenuationDb: (v: number) => void;
+  resetLoudnessPreAnalysisAttenuationDbDefault: () => void;
   setReplayGainMode: (v: 'track' | 'album' | 'auto') => void;
   setReplayGainPreGainDb: (v: number) => void;
   setReplayGainFallbackDb: (v: number) => void;
@@ -319,6 +349,9 @@ export const useAuthStore = create<AuthState>()(
       excludeAudiobooks: false,
       customGenreBlacklist: [],
       replayGainEnabled: false,
+      normalizationEngine: 'off',
+      loudnessTargetLufs: -12,
+      loudnessPreAnalysisAttenuationDb: DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB,
       replayGainMode: 'auto',
       replayGainPreGainDb: 0,
       replayGainFallbackDb: 0,
@@ -447,6 +480,21 @@ export const useAuthStore = create<AuthState>()(
         set({ replayGainEnabled: v });
         usePlayerStore.getState().updateReplayGainForCurrentTrack();
       },
+      setNormalizationEngine: (v) => {
+        set({ normalizationEngine: v });
+        usePlayerStore.getState().updateReplayGainForCurrentTrack();
+      },
+      setLoudnessTargetLufs: (v) => {
+        set({ loudnessTargetLufs: v });
+        usePlayerStore.getState().updateReplayGainForCurrentTrack();
+      },
+      setLoudnessPreAnalysisAttenuationDb: (v) => {
+        set({ loudnessPreAnalysisAttenuationDb: clampLoudnessPreAnalysisAttenuationDb(v) });
+      },
+      resetLoudnessPreAnalysisAttenuationDbDefault: () => {
+        set({ loudnessPreAnalysisAttenuationDb: DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB });
+        usePlayerStore.getState().updateReplayGainForCurrentTrack();
+      },
       setReplayGainMode: (v) => {
         set({ replayGainMode: v });
         usePlayerStore.getState().updateReplayGainForCurrentTrack();
@@ -681,6 +729,10 @@ export const useAuthStore = create<AuthState>()(
           } catch { /* ignore */ }
         }
 
+        const st = state as { loudnessTargetLufs?: unknown; loudnessPreAnalysisAttenuationDb?: unknown };
+        const targetSan = sanitizeLoudnessLufsPreset(st.loudnessTargetLufs, -12);
+        const preSan = clampLoudnessPreAnalysisAttenuationDb(st.loudnessPreAnalysisAttenuationDb);
+
         useAuthStore.setState({
           mixMinRatingSong: clampMixFilterMinStars(state.mixMinRatingSong as number),
           mixMinRatingAlbum: clampMixFilterMinStars(state.mixMinRatingAlbum as number),
@@ -688,6 +740,8 @@ export const useAuthStore = create<AuthState>()(
           skipStarManualSkipCountsByKey: sanitizeSkipStarCounts(
             (state as { skipStarManualSkipCountsByKey?: unknown }).skipStarManualSkipCountsByKey,
           ),
+          loudnessTargetLufs: targetSan,
+          loudnessPreAnalysisAttenuationDb: preSan,
           ...conflictingLegacyState,
           ...lyricsSourcesMigrated,
           ...wheelSmoothOneTime,

src/store/hotCacheStore.ts

@@ -3,6 +3,7 @@ import { persist, createJSONStorage } from 'zustand/middleware';
 import { invoke } from '@tauri-apps/api/core';
 import { isHotCachePreviousTrackUnderGrace } from '../utils/hotCacheGate';
 import type { Track } from './playerStore';
+import { emitAnalysisStorageChanged } from './analysisSync';
 
 /** How many queue slots after the current index are eviction-protected (1 = current + next only). */
 export const HOT_CACHE_PROTECT_AFTER_CURRENT = 1;
@@ -96,6 +97,7 @@ export const useHotCacheStore = create<HotCacheState>()(
           delete next[entryKey(serverId, trackId)];
           return { entries: next };
         });
+        emitAnalysisStorageChanged({ trackId, reason: 'hotcache-delete' });
       },
 
       totalBytes: () =>
@@ -167,6 +169,7 @@ export const useHotCacheStore = create<HotCacheState>()(
           }).catch(() => {});
           sum -= meta.sizeBytes || 0;
           delete entries[key];
+          emitAnalysisStorageChanged({ trackId: parsed.trackId, reason: 'hotcache-delete' });
         }
 
         set({ entries });
@@ -175,6 +178,7 @@ export const useHotCacheStore = create<HotCacheState>()(
       clearAllDisk: async (customDir: string | null) => {
         await invoke('purge_hot_cache', { customDir: customDir || null }).catch(() => {});
         set({ entries: {} });
+        emitAnalysisStorageChanged({ trackId: null, reason: 'hotcache-purge' });
       },
     }),
     {

src/store/offlineStore.ts

@@ -6,6 +6,7 @@ import type { SubsonicSong } from '../api/subsonic';
 import { useAuthStore } from './authStore';
 import { showToast } from '../utils/toast';
 import { useOfflineJobStore, cancelledDownloads } from './offlineJobStore';
+import { emitAnalysisStorageChanged } from './analysisSync';
 
 export interface OfflineTrackMeta {
   id: string;
@@ -299,6 +300,9 @@ export const useOfflineStore = create<OfflineState>()(
             }).catch(() => {});
           }),
         );
+        for (const trackId of album.trackIds) {
+          emitAnalysisStorageChanged({ trackId, reason: 'offline-delete' });
+        }
 
         set(state => {
           const tracks = { ...state.tracks };

src/store/playerStore.ts

@@ -10,6 +10,7 @@ import { lastfmScrobble, lastfmUpdateNowPlaying, lastfmLoveTrack, lastfmUnloveTr
 import { useAuthStore } from './authStore';
 import { useOfflineStore } from './offlineStore';
 import { useHotCacheStore } from './hotCacheStore';
+import { onAnalysisStorageChanged } from './analysisSync';
 import { orbitBulkGuard } from '../utils/orbitBulkGuard';
 import { useOrbitStore } from './orbitStore';
 import { estimateLivePosition } from '../api/orbit';
@@ -146,6 +147,16 @@ async function buildInfiniteQueueCandidates(
 
 interface PlayerState {
   currentTrack: Track | null;
+  waveformBins: number[] | null;
+  normalizationNowDb: number | null;
+  normalizationTargetLufs: number | null;
+  normalizationEngineLive: 'off' | 'replaygain' | 'loudness';
+  normalizationDbgSource: string | null;
+  normalizationDbgTrackId: string | null;
+  normalizationDbgCacheGainDb: number | null;
+  normalizationDbgCacheTargetLufs: number | null;
+  normalizationDbgCacheUpdatedAt: number | null;
+  normalizationDbgLastEventAt: number | null;
   currentRadio: InternetRadioStation | null;
   /** Latches the source used to start the currently playing track. */
   currentPlaybackSource: PlaybackSourceKind | null;
@@ -195,8 +206,9 @@ interface PlayerState {
   next: (manual?: boolean) => void;
   previous: () => void;
   seek: (progress: number) => void;
-  setVolume: (v: number) => void;
+   setVolume: (v: number) => void;
    updateReplayGainForCurrentTrack: () => void;
+   reanalyzeLoudnessForTrack: (trackId: string) => Promise<void>;
    setProgress: (t: number, duration: number) => void;
   enqueue: (tracks: Track[], _orbitConfirmed?: boolean) => void;
   enqueueAt: (tracks: Track[], insertIndex: number, _orbitConfirmed?: boolean) => void;
@@ -248,6 +260,51 @@ interface PlayerState {
   closeSongInfo: () => void;
 }
 
+type WaveformCachePayload = {
+  /** May be `number[]` or `Uint8Array` depending on Tauri IPC / serde path. */
+  bins: number[] | Uint8Array;
+  binCount: number;
+  isPartial: boolean;
+  knownUntilSec: number;
+  durationSec: number;
+  updatedAt: number;
+};
+
+/** `Vec<u8>` from Rust often arrives as `Uint8Array`, not `Array.isArray`. */
+function coerceWaveformBins(bins: unknown): number[] | null {
+  if (bins == null) return null;
+  if (Array.isArray(bins)) {
+    return bins.length > 0 ? bins.map(x => Number(x) & 255) : null;
+  }
+  if (bins instanceof Uint8Array) {
+    return bins.length > 0 ? Array.from(bins) : null;
+  }
+  if (typeof bins === 'object' && 'length' in bins && typeof (bins as { length: unknown }).length === 'number') {
+    const len = (bins as { length: number }).length;
+    if (len === 0) return null;
+    try {
+      return Array.from(bins as ArrayLike<number>).map(x => Number(x) & 255);
+    } catch {
+      return null;
+    }
+  }
+  return null;
+}
+
+type LoudnessCachePayload = {
+  integratedLufs: number;
+  truePeak: number;
+  recommendedGainDb: number;
+  targetLufs: number;
+  updatedAt: number;
+};
+
+type NormalizationStatePayload = {
+  engine: 'off' | 'replaygain' | 'loudness' | string;
+  currentGainDb: number | null;
+  targetLufs: number;
+};
+
 // ─── Module-level playback primitives ─────────────────────────────────────────
 
 // isAudioPaused — true when the Rust audio engine has a loaded-but-paused track.
@@ -266,6 +323,66 @@ let radioFetching = false;
 // Artist ID used to start the current radio session — persists across track
 // advances so proactive loading works even when songs lack artistId.
 let currentRadioArtistId: string | null = null;
+let cachedLoudnessGainByTrackId: Record<string, number> = {};
+let stableLoudnessGainByTrackId: Record<string, true> = {};
+let lastNormalizationUiUpdateAtMs = 0;
+
+function emitNormalizationDebug(step: string, details?: Record<string, unknown>) {
+  if (useAuthStore.getState().loggingMode !== 'debug') return;
+  void invoke('frontend_debug_log', {
+    scope: 'normalization',
+    message: JSON.stringify({ step, details }),
+  }).catch(() => {});
+}
+
+function normalizeAnalysisTrackId(trackId?: string | null): string | null {
+  if (!trackId) return null;
+  if (trackId.startsWith('stream:')) return trackId.slice('stream:'.length);
+  return trackId;
+}
+
+function normalizationAlmostEqual(a: number | null, b: number | null, eps = 0.12): boolean {
+  if (a == null && b == null) return true;
+  if (a == null || b == null) return false;
+  return Math.abs(a - b) <= eps;
+}
+
+function deriveNormalizationSnapshot(
+  track: Track,
+  queue: Track[],
+  queueIndex: number,
+): Pick<
+  PlayerState,
+  'normalizationNowDb' | 'normalizationTargetLufs' | 'normalizationEngineLive'
+> {
+  const auth = useAuthStore.getState();
+  const engine = auth.normalizationEngine;
+  if (engine === 'loudness') {
+    const target = auth.loudnessTargetLufs;
+    return {
+      // Clears stale UI until `audio:normalization-state` / refresh catches up.
+      normalizationNowDb: null,
+      normalizationTargetLufs: target,
+      normalizationEngineLive: 'loudness',
+    };
+  }
+  if (engine === 'replaygain' && auth.replayGainEnabled) {
+    const prev = queueIndex > 0 ? queue[queueIndex - 1] : null;
+    const next = queueIndex + 1 < queue.length ? queue[queueIndex + 1] : null;
+    const resolved = resolveReplayGainDb(track, prev, next, true, auth.replayGainMode);
+    const nowDb = resolved != null ? (resolved + auth.replayGainPreGainDb) : auth.replayGainFallbackDb;
+    return {
+      normalizationNowDb: nowDb,
+      normalizationTargetLufs: null,
+      normalizationEngineLive: 'replaygain',
+    };
+  }
+  return {
+    normalizationNowDb: null,
+    normalizationTargetLufs: null,
+    normalizationEngineLive: 'off',
+  };
+}
 
 // Debounce timer for seek slider drags.
 let seekDebounce: ReturnType<typeof setTimeout> | null = null;
@@ -274,6 +391,9 @@ let seekDebounce: ReturnType<typeof setTimeout> | null = null;
 let seekTarget: number | null = null;
 let seekTargetSetAt = 0;
 const SEEK_TARGET_GUARD_TIMEOUT_MS = 5000;
+const analysisBackfillInFlightByTrackId: Record<string, true> = {};
+const analysisBackfillAttemptsByTrackId: Record<string, number> = {};
+const MAX_BACKFILL_ATTEMPTS_PER_TRACK = 2;
 // Streaming fallback seek guard: coalesce repeated "not seekable" recoveries.
 let seekFallbackRetryTimer: ReturnType<typeof setTimeout> | null = null;
 let seekFallbackRetryStartedAt = 0;
@@ -488,6 +608,185 @@ function touchHotCacheOnPlayback(trackId: string, serverId: string) {
   useHotCacheStore.getState().touchPlayed(trackId, serverId);
 }
 
+function isReplayGainActive() {
+  const a = useAuthStore.getState();
+  return a.normalizationEngine === 'replaygain' && a.replayGainEnabled;
+}
+
+function loudnessCacheStateKeysForTrackId(trackId: string): string[] {
+  if (!trackId) return [];
+  const out: string[] = [trackId];
+  if (trackId.startsWith('stream:')) {
+    const bare = trackId.slice('stream:'.length);
+    if (bare) out.push(bare);
+  } else {
+    out.push(`stream:${trackId}`);
+  }
+  return out;
+}
+
+function clearLoudnessCacheStateForTrackId(trackId: string) {
+  for (const k of loudnessCacheStateKeysForTrackId(trackId)) {
+    delete cachedLoudnessGainByTrackId[k];
+    delete stableLoudnessGainByTrackId[k];
+  }
+}
+
+/** Pass to `audio_play` / `audio_chain_preload` only — DB-backed gain. Omit partial hints so Rust uses pre-trim until `analysis:loudness-partial` + `audio_update_replay_gain`. */
+function loudnessGainDbForEngineBind(trackId: string | undefined | null): number | null {
+  if (!trackId) return null;
+  if (!stableLoudnessGainByTrackId[trackId]) return null;
+  const v = cachedLoudnessGainByTrackId[trackId];
+  return Number.isFinite(v) ? v : null;
+}
+
+function resetLoudnessBackfillStateForTrackId(trackId: string) {
+  for (const k of loudnessCacheStateKeysForTrackId(trackId)) {
+    delete analysisBackfillInFlightByTrackId[k];
+    analysisBackfillAttemptsByTrackId[k] = 0;
+  }
+}
+
+async function reseedLoudnessForTrackId(trackId: string) {
+  if (!trackId) return;
+  const auth = useAuthStore.getState();
+  if (auth.normalizationEngine !== 'loudness') return;
+  clearLoudnessCacheStateForTrackId(trackId);
+  resetLoudnessBackfillStateForTrackId(trackId);
+  if (auth.normalizationEngine === 'loudness') {
+    usePlayerStore.setState({
+      normalizationNowDb: null,
+      normalizationTargetLufs: auth.loudnessTargetLufs,
+      normalizationEngineLive: 'loudness',
+    });
+  }
+  try {
+    await invoke('analysis_delete_loudness_for_track', { trackId });
+  } catch (e) {
+    console.error('[psysonic] analysis_delete_loudness_for_track failed:', e);
+  }
+  usePlayerStore.getState().updateReplayGainForCurrentTrack();
+  const url = buildStreamUrl(trackId);
+  try {
+    await invoke('analysis_enqueue_seed_from_url', { trackId, url });
+  } catch (e) {
+    console.error('[psysonic] analysis_enqueue_seed_from_url (reseed) failed:', e);
+  }
+}
+
+async function refreshWaveformForTrack(trackId: string) {
+  if (!trackId) return;
+  try {
+    const row = await invoke<WaveformCachePayload | null>('analysis_get_waveform_for_track', { trackId });
+    // Never apply bins for a non-current track (e.g. gapless byte-preload fetches the neighbour).
+    if (usePlayerStore.getState().currentTrack?.id !== trackId) return;
+    const bins = row ? coerceWaveformBins(row.bins) : null;
+    if (!bins || bins.length === 0) {
+      usePlayerStore.setState({
+        waveformBins: null,
+      });
+      return;
+    }
+    usePlayerStore.setState({
+      waveformBins: bins,
+    });
+  } catch {
+    // best-effort; seekbar falls back to placeholder waveform
+  }
+}
+
+/** When `syncPlayingEngine` is false, only update `cachedLoudnessGainByTrackId` (e.g. queue neighbour) — do not call `audio_update_replay_gain` for the already-playing track. */
+async function refreshLoudnessForTrack(
+  trackId: string,
+  opts?: { syncPlayingEngine?: boolean },
+) {
+  if (!trackId) return;
+  const syncEngine = opts?.syncPlayingEngine !== false;
+  emitNormalizationDebug('refresh:start', { trackId });
+  usePlayerStore.setState({ normalizationDbgSource: 'refresh:start', normalizationDbgTrackId: trackId });
+  try {
+    const row = await invoke<LoudnessCachePayload | null>('analysis_get_loudness_for_track', {
+      trackId,
+      targetLufs: useAuthStore.getState().loudnessTargetLufs,
+    });
+    if (!row || !Number.isFinite(row.recommendedGainDb)) {
+      delete cachedLoudnessGainByTrackId[trackId];
+      delete stableLoudnessGainByTrackId[trackId];
+      emitNormalizationDebug('refresh:miss', { trackId, row: row ?? null });
+      const auth = useAuthStore.getState();
+      const attempts = analysisBackfillAttemptsByTrackId[trackId] ?? 0;
+      if (auth.normalizationEngine === 'loudness'
+        && !analysisBackfillInFlightByTrackId[trackId]
+        && attempts < MAX_BACKFILL_ATTEMPTS_PER_TRACK) {
+        analysisBackfillInFlightByTrackId[trackId] = true;
+        analysisBackfillAttemptsByTrackId[trackId] = attempts + 1;
+        const url = buildStreamUrl(trackId);
+        emitNormalizationDebug('backfill:enqueue', { trackId, url, attempt: attempts + 1 });
+        void invoke('analysis_enqueue_seed_from_url', { trackId, url })
+          .then(() => emitNormalizationDebug('backfill:queued', { trackId, attempt: attempts + 1 }))
+          .catch((e) => emitNormalizationDebug('backfill:error', { trackId, error: String(e) }))
+          .finally(() => {
+            delete analysisBackfillInFlightByTrackId[trackId];
+          });
+      } else if (auth.normalizationEngine === 'loudness' && attempts >= MAX_BACKFILL_ATTEMPTS_PER_TRACK) {
+        emitNormalizationDebug('backfill:throttled', { trackId, attempts });
+      }
+      usePlayerStore.setState({
+        normalizationDbgSource: 'refresh:miss',
+        normalizationDbgTrackId: trackId,
+        normalizationDbgCacheGainDb: null,
+        normalizationDbgCacheTargetLufs: Number.isFinite(row?.targetLufs as number) ? (row?.targetLufs as number) : null,
+        normalizationDbgCacheUpdatedAt: Number.isFinite(row?.updatedAt as number) ? (row?.updatedAt as number) : null,
+      });
+      return;
+    }
+    cachedLoudnessGainByTrackId[trackId] = row.recommendedGainDb;
+    stableLoudnessGainByTrackId[trackId] = true;
+    analysisBackfillAttemptsByTrackId[trackId] = 0;
+    emitNormalizationDebug('refresh:hit', { trackId, row });
+    usePlayerStore.setState({
+      normalizationDbgSource: 'refresh:hit',
+      normalizationDbgTrackId: trackId,
+      normalizationDbgCacheGainDb: row.recommendedGainDb,
+      normalizationDbgCacheTargetLufs: Number.isFinite(row.targetLufs) ? row.targetLufs : null,
+      normalizationDbgCacheUpdatedAt: Number.isFinite(row.updatedAt) ? row.updatedAt : null,
+    });
+    if (syncEngine) {
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    }
+  } catch {
+    delete cachedLoudnessGainByTrackId[trackId];
+    delete stableLoudnessGainByTrackId[trackId];
+    emitNormalizationDebug('refresh:error', { trackId });
+    usePlayerStore.setState({ normalizationDbgSource: 'refresh:error', normalizationDbgTrackId: trackId });
+  }
+}
+
+/** After bulk enqueue, warm loudness cache so gapless `audio_chain_preload` sees real gain, not only startup trim. */
+const LOUDNESS_PREFETCH_MAX_ENQUEUED_IDS = 40;
+
+function prefetchLoudnessForEnqueuedTracks(
+  incoming: Track[],
+  mergedQueue: Track[],
+  queueIndex: number,
+) {
+  if (useAuthStore.getState().normalizationEngine !== 'loudness') return;
+  const ids = new Set<string>();
+  const next = mergedQueue[queueIndex + 1];
+  if (next?.id) ids.add(next.id);
+  let n = 0;
+  for (const t of incoming) {
+    if (n >= LOUDNESS_PREFETCH_MAX_ENQUEUED_IDS) break;
+    if (t?.id) {
+      ids.add(t.id);
+      n++;
+    }
+  }
+  for (const id of ids) {
+    void refreshLoudnessForTrack(id, { syncPlayingEngine: false });
+  }
+}
+
 async function promoteCompletedStreamToHotCache(track: Track, serverId: string, customDir: string | null) {
   try {
     const res = await invoke<{ path: string; size: number } | null>(
@@ -648,6 +947,9 @@ function handleAudioProgress(current_time: number, duration: number) {
     // Byte pre-download — runs early so bytes are cached by chain time.
     if ((shouldBytePreload || shouldBytePreloadForGaplessBackup) && nextTrack.id !== bytePreloadingId) {
       bytePreloadingId = nextTrack.id;
+      // Loudness cache only — do not call refreshWaveformForTrack(next): it writes global
+      // waveformBins and would replace the current track's seekbar while still playing it.
+      void refreshLoudnessForTrack(nextTrack.id, { syncPlayingEngine: false });
       if (import.meta.env.DEV) {
         console.info('[psysonic][preload-request]', {
           nextTrackId: nextTrack.id,
@@ -658,12 +960,18 @@ function handleAudioProgress(current_time: number, duration: number) {
           gaplessEnabled,
         });
       }
-      invoke('audio_preload', { url: nextUrl, durationHint: nextTrack.duration }).catch(() => {});
+      invoke('audio_preload', {
+        url: nextUrl,
+        durationHint: nextTrack.duration,
+        analysisTrackId: nextTrack.id,
+      }).catch(() => {});
     }
 
     // Gapless chain — decode + chain into Sink 30s before track boundary.
     if (shouldChainGapless && nextTrack.id !== gaplessPreloadingId) {
       gaplessPreloadingId = nextTrack.id;
+      // Ensure loudness gain is already cached for the chained request payload.
+      void refreshLoudnessForTrack(nextTrack.id, { syncPlayingEngine: false });
       const authState = useAuthStore.getState();
       // Auto-mode neighbours for the *next* track: current track on its left,
       // queue[nextIdx+1] on its right.
@@ -672,9 +980,9 @@ function handleAudioProgress(current_time: number, duration: number) {
         : (repeatMode === 'all' && queue.length > 0 ? queue[0] : null);
       const replayGainDb = resolveReplayGainDb(
         nextTrack, track, nextNeighbour,
-        authState.replayGainEnabled, authState.replayGainMode,
+        isReplayGainActive(), authState.replayGainMode,
       );
-      const replayGainPeak = authState.replayGainEnabled
+      const replayGainPeak = isReplayGainActive()
         ? (nextTrack.replayGainPeak ?? null)
         : null;
       invoke('audio_chain_preload', {
@@ -683,9 +991,11 @@ function handleAudioProgress(current_time: number, duration: number) {
         durationHint: nextTrack.duration,
         replayGainDb,
         replayGainPeak,
+        loudnessGainDb: loudnessGainDbForEngineBind(nextTrack.id),
         preGainDb: authState.replayGainPreGainDb,
         fallbackDb: authState.replayGainFallbackDb,
         hiResEnabled: authState.enableHiRes,
+        analysisTrackId: nextTrack.id,
       }).catch(() => {});
     }
   }
@@ -707,7 +1017,12 @@ function handleAudioEnded() {
 
   const { repeatMode, currentTrack, queue } = usePlayerStore.getState();
   isAudioPaused = false;
-  usePlayerStore.setState({ isPlaying: false, progress: 0, currentTime: 0, buffered: 0 });
+  usePlayerStore.setState({
+    isPlaying: false,
+    progress: 0,
+    currentTime: 0,
+    buffered: 0,
+  });
   setTimeout(() => {
     if (repeatMode === 'one' && currentTrack) {
       usePlayerStore.getState().playTrack(currentTrack, queue, false);
@@ -751,6 +1066,10 @@ function handleAudioTrackSwitched(duration: number) {
 
   usePlayerStore.setState({
     currentTrack: nextTrack,
+    waveformBins: null,
+    ...deriveNormalizationSnapshot(nextTrack, queue, newIndex),
+    normalizationDbgSource: 'track-switched',
+    normalizationDbgTrackId: nextTrack.id,
     queueIndex: newIndex,
     isPlaying: true,
     progress: 0,
@@ -759,6 +1078,14 @@ function handleAudioTrackSwitched(duration: number) {
     scrobbled: false,
     lastfmLoved: false,
   });
+  emitNormalizationDebug('track-switched', {
+    trackId: nextTrack.id,
+    queueIndex: newIndex,
+    engineRequested: useAuthStore.getState().normalizationEngine,
+  });
+  void refreshWaveformForTrack(nextTrack.id);
+  void refreshLoudnessForTrack(nextTrack.id);
+  usePlayerStore.getState().updateReplayGainForCurrentTrack();
 
   // Report Now Playing to Navidrome + Last.fm
   const { nowPlayingEnabled, scrobblingEnabled, lastfmSessionKey } = useAuthStore.getState();
@@ -824,6 +1151,83 @@ export function initAudioListeners(): () => void {
     listen<void>('audio:ended', () => handleAudioEnded()),
     listen<string>('audio:error', ({ payload }) => handleAudioError(payload)),
     listen<number>('audio:track_switched', ({ payload }) => handleAudioTrackSwitched(payload)),
+    listen<{ trackId?: string | null; gainDb: number; targetLufs: number; isPartial: boolean }>('analysis:loudness-partial', ({ payload }) => {
+      const current = usePlayerStore.getState().currentTrack;
+      if (!current || !payload) return;
+      const payloadTrackId = normalizeAnalysisTrackId(payload.trackId);
+      if (payloadTrackId && payloadTrackId !== current.id) return;
+      if (!Number.isFinite(payload.gainDb)) return;
+      if (stableLoudnessGainByTrackId[current.id]) return;
+      cachedLoudnessGainByTrackId[current.id] = payload.gainDb;
+      emitNormalizationDebug('partial-loudness:apply', {
+        trackId: current.id,
+        gainDb: payload.gainDb,
+        targetLufs: payload.targetLufs,
+      });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    }),
+    listen<{ trackId: string; isPartial: boolean }>('analysis:waveform-updated', ({ payload }) => {
+      if (!payload?.trackId) return;
+      const payloadTrackId = normalizeAnalysisTrackId(payload.trackId);
+      if (!payloadTrackId) return;
+      const currentRaw = usePlayerStore.getState().currentTrack?.id;
+      const currentId = currentRaw ? normalizeAnalysisTrackId(currentRaw) : null;
+      if (currentId && payloadTrackId === currentId) {
+        void refreshWaveformForTrack(currentRaw!);
+        void refreshLoudnessForTrack(currentId);
+        emitNormalizationDebug('backfill:applied', { trackId: currentId });
+        return;
+      }
+      // Backfill finished for another id (e.g. next in queue): refresh loudness cache only
+      // so `cachedLoudnessGainByTrackId` is ready before `audio_play` / gapless chain.
+      void refreshLoudnessForTrack(payloadTrackId, { syncPlayingEngine: false });
+      emitNormalizationDebug('backfill:applied', { trackId: payloadTrackId });
+    }),
+    listen<NormalizationStatePayload>('audio:normalization-state', ({ payload }) => {
+      if (!payload) return;
+      const engine =
+        payload.engine === 'loudness' || payload.engine === 'replaygain'
+          ? payload.engine
+          : 'off';
+      const nowDb = Number.isFinite(payload.currentGainDb as number) ? (payload.currentGainDb as number) : null;
+      const targetLufs = Number.isFinite(payload.targetLufs) ? payload.targetLufs : null;
+      const prev = usePlayerStore.getState();
+      // Avoid UI flicker from noisy duplicate emits and transient nulls.
+      if (
+        engine === prev.normalizationEngineLive
+        && normalizationAlmostEqual(nowDb, prev.normalizationNowDb)
+        && normalizationAlmostEqual(targetLufs, prev.normalizationTargetLufs, 0.02)
+      ) {
+        return;
+      }
+      if (engine === 'loudness' && nowDb == null && prev.normalizationNowDb != null) {
+        return;
+      }
+      const nowMs = Date.now();
+      const isFirstNumericGain =
+        engine === 'loudness'
+        && nowDb != null
+        && prev.normalizationNowDb == null;
+      if (
+        !isFirstNumericGain
+        && nowMs - lastNormalizationUiUpdateAtMs < 120
+        && engine === prev.normalizationEngineLive
+      ) {
+        return;
+      }
+      lastNormalizationUiUpdateAtMs = nowMs;
+      emitNormalizationDebug('event:audio:normalization-state', {
+        trackId: usePlayerStore.getState().currentTrack?.id ?? null,
+        payload,
+      });
+      usePlayerStore.setState({
+        normalizationEngineLive: engine,
+        normalizationNowDb: nowDb,
+        normalizationTargetLufs: targetLufs,
+        normalizationDbgSource: 'event:audio:normalization-state',
+        normalizationDbgLastEventAt: Date.now(),
+      });
+    }),
     listen<string>('audio:preload-ready', ({ payload }) => {
       const tid = streamUrlTrackId(payload);
       if (import.meta.env.DEV) {
@@ -847,17 +1251,98 @@ export function initAudioListeners(): () => void {
   const { crossfadeEnabled, crossfadeSecs, gaplessEnabled, audioOutputDevice } = useAuthStore.getState();
   invoke('audio_set_crossfade', { enabled: crossfadeEnabled, secs: crossfadeSecs }).catch(() => {});
   invoke('audio_set_gapless', { enabled: gaplessEnabled }).catch(() => {});
+  const normCfg = useAuthStore.getState();
+  usePlayerStore.setState({
+    normalizationEngineLive: normCfg.normalizationEngine,
+    normalizationTargetLufs: normCfg.normalizationEngine === 'loudness' ? normCfg.loudnessTargetLufs : null,
+    normalizationNowDb: null,
+    normalizationDbgSource: 'init:set-normalization',
+  });
+  emitNormalizationDebug('init:set-normalization', {
+    engine: normCfg.normalizationEngine,
+    targetLufs: normCfg.loudnessTargetLufs,
+    currentTrackId: usePlayerStore.getState().currentTrack?.id ?? null,
+  });
+  invoke('audio_set_normalization', {
+    engine: normCfg.normalizationEngine,
+    targetLufs: normCfg.loudnessTargetLufs,
+    preAnalysisAttenuationDb: normCfg.loudnessPreAnalysisAttenuationDb,
+  }).catch(() => {});
+  const bootTrackId = usePlayerStore.getState().currentTrack?.id;
+  if (bootTrackId) {
+    void refreshWaveformForTrack(bootTrackId);
+  }
+  if (normCfg.normalizationEngine === 'loudness') {
+    const currentId = usePlayerStore.getState().currentTrack?.id;
+    if (currentId) {
+      void refreshLoudnessForTrack(currentId).finally(() => {
+        usePlayerStore.getState().updateReplayGainForCurrentTrack();
+      });
+    }
+  }
   if (audioOutputDevice) {
     invoke('audio_set_device', { deviceName: audioOutputDevice }).catch(() => {});
   }
 
   // Keep audio settings in sync whenever auth store changes.
+  let prevNormEngine = normCfg.normalizationEngine;
+  let prevNormTarget = normCfg.loudnessTargetLufs;
+  let prevPreAnalysis = normCfg.loudnessPreAnalysisAttenuationDb;
   const unsubAuth = useAuthStore.subscribe((state) => {
     invoke('audio_set_crossfade', {
       enabled: state.crossfadeEnabled,
       secs: state.crossfadeSecs,
     }).catch(() => {});
     invoke('audio_set_gapless', { enabled: state.gaplessEnabled }).catch(() => {});
+    const normChanged =
+      state.normalizationEngine !== prevNormEngine
+      || state.loudnessTargetLufs !== prevNormTarget
+      || state.loudnessPreAnalysisAttenuationDb !== prevPreAnalysis;
+    if (!normChanged) return;
+    const onlyPreAnalysisChanged =
+      state.normalizationEngine === prevNormEngine
+      && state.loudnessTargetLufs === prevNormTarget
+      && state.loudnessPreAnalysisAttenuationDb !== prevPreAnalysis;
+    prevNormEngine = state.normalizationEngine;
+    prevNormTarget = state.loudnessTargetLufs;
+    prevPreAnalysis = state.loudnessPreAnalysisAttenuationDb;
+    usePlayerStore.setState({
+      normalizationEngineLive: state.normalizationEngine,
+      normalizationTargetLufs: state.normalizationEngine === 'loudness' ? state.loudnessTargetLufs : null,
+      normalizationNowDb: state.normalizationEngine === 'loudness'
+        ? usePlayerStore.getState().normalizationNowDb
+        : null,
+      normalizationDbgSource: 'auth:normalization-changed',
+    });
+    emitNormalizationDebug('auth:normalization-changed', {
+      engine: state.normalizationEngine,
+      targetLufs: state.loudnessTargetLufs,
+      currentTrackId: usePlayerStore.getState().currentTrack?.id ?? null,
+    });
+    invoke('audio_set_normalization', {
+      engine: state.normalizationEngine,
+      targetLufs: state.loudnessTargetLufs,
+      preAnalysisAttenuationDb: state.loudnessPreAnalysisAttenuationDb,
+    }).catch(() => {});
+    if (state.normalizationEngine === 'loudness') {
+      const currentId = usePlayerStore.getState().currentTrack?.id;
+      if (onlyPreAnalysisChanged) {
+        usePlayerStore.getState().updateReplayGainForCurrentTrack();
+      } else if (currentId) {
+        void refreshLoudnessForTrack(currentId).finally(() => {
+          usePlayerStore.getState().updateReplayGainForCurrentTrack();
+        });
+      }
+    } else {
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    }
+  });
+  const unsubAnalysisSync = onAnalysisStorageChanged(detail => {
+    const currentId = usePlayerStore.getState().currentTrack?.id;
+    if (!currentId) return;
+    if (detail.trackId && detail.trackId !== currentId) return;
+    void refreshWaveformForTrack(currentId);
+    void refreshLoudnessForTrack(currentId);
   });
 
   // ── MPRIS / OS media controls sync ───────────────────────────────────────
@@ -1019,6 +1504,7 @@ export function initAudioListeners(): () => void {
 
   return () => {
     unsubAuth();
+    unsubAnalysisSync();
     unsubMpris();
     unsubDiscordPlayer();
     unsubDiscordAuth();
@@ -1033,6 +1519,16 @@ export const usePlayerStore = create<PlayerState>()(
   persist(
     (set, get) => ({
       currentTrack: null,
+      waveformBins: null,
+      normalizationNowDb: null,
+      normalizationTargetLufs: null,
+      normalizationEngineLive: 'off',
+      normalizationDbgSource: null,
+      normalizationDbgTrackId: null,
+      normalizationDbgCacheGainDb: null,
+      normalizationDbgCacheTargetLufs: null,
+      normalizationDbgCacheUpdatedAt: null,
+      normalizationDbgLastEventAt: null,
       currentRadio: null,
       currentPlaybackSource: null,
       enginePreloadedTrackId: null,
@@ -1159,6 +1655,10 @@ export const usePlayerStore = create<PlayerState>()(
           buffered: 0,
           currentTime: 0,
           currentRadio: null,
+          waveformBins: null,
+          normalizationNowDb: null,
+          normalizationTargetLufs: null,
+          normalizationEngineLive: 'off',
           currentPlaybackSource: null,
           enginePreloadedTrackId: null,
           scheduledPauseAtMs: null,
@@ -1199,6 +1699,10 @@ export const usePlayerStore = create<PlayerState>()(
         set({
           currentRadio: station,
           currentTrack: null,
+          waveformBins: null,
+          normalizationNowDb: null,
+          normalizationTargetLufs: null,
+          normalizationEngineLive: 'off',
           currentPlaybackSource: null,
           queue: [],
           queueIndex: 0,
@@ -1306,6 +1810,8 @@ export const usePlayerStore = create<PlayerState>()(
         set({
           currentTrack: track,
           currentRadio: null,
+          waveformBins: null,
+          ...deriveNormalizationSnapshot(track, newQueue, idx >= 0 ? idx : 0),
           queue: newQueue,
           queueIndex: idx >= 0 ? idx : 0,
           progress: initialProgress,
@@ -1330,24 +1836,28 @@ export const usePlayerStore = create<PlayerState>()(
             authState.hotCacheDownloadDir || null,
           );
         }
+        void refreshWaveformForTrack(track.id);
+        void refreshLoudnessForTrack(track.id);
         setDeferHotCachePrefetch(true);
         const playIdx = idx >= 0 ? idx : 0;
         const nextNeighbour = playIdx + 1 < newQueue.length ? newQueue[playIdx + 1] : null;
         const replayGainDb = resolveReplayGainDb(
           track, prevTrack, nextNeighbour,
-          authState.replayGainEnabled, authState.replayGainMode,
+          isReplayGainActive(), authState.replayGainMode,
         );
-        const replayGainPeak = authState.replayGainEnabled ? (track.replayGainPeak ?? null) : null;
+        const replayGainPeak = isReplayGainActive() ? (track.replayGainPeak ?? null) : null;
         invoke('audio_play', {
           url,
           volume: state.volume,
           durationHint: track.duration,
           replayGainDb,
           replayGainPeak,
+          loudnessGainDb: loudnessGainDbForEngineBind(track.id),
           preGainDb: authState.replayGainPreGainDb,
           fallbackDb: authState.replayGainFallbackDb,
           manual,
           hiResEnabled: authState.enableHiRes,
+          analysisTrackId: track.id,
         })
           .then(() => {
             if (playGeneration !== gen) return;
@@ -1511,9 +2021,9 @@ export const usePlayerStore = create<PlayerState>()(
             const authStateCold = useAuthStore.getState();
             const replayGainDbCold = resolveReplayGainDb(
               trackToPlay, coldPrev, coldNext,
-              authStateCold.replayGainEnabled, authStateCold.replayGainMode,
+              isReplayGainActive(), authStateCold.replayGainMode,
             );
-            const replayGainPeakCold = authStateCold.replayGainEnabled ? (trackToPlay.replayGainPeak ?? null) : null;
+            const replayGainPeakCold = isReplayGainActive() ? (trackToPlay.replayGainPeak ?? null) : null;
             const coldServerId = useAuthStore.getState().activeServerId ?? '';
             setDeferHotCachePrefetch(true);
             const coldUrl = resolvePlaybackUrl(trackToPlay.id, coldServerId);
@@ -1524,10 +2034,12 @@ export const usePlayerStore = create<PlayerState>()(
               durationHint: trackToPlay.duration,
               replayGainDb: replayGainDbCold,
               replayGainPeak: replayGainPeakCold,
+              loudnessGainDb: loudnessGainDbForEngineBind(trackToPlay.id),
               preGainDb: authStateCold.replayGainPreGainDb,
               fallbackDb: authStateCold.replayGainFallbackDb,
               manual: false,
               hiResEnabled: useAuthStore.getState().enableHiRes,
+              analysisTrackId: trackToPlay.id,
             }).then(() => {
               if (playGeneration === gen && currentTime > 1) {
                 invoke('audio_seek', { seconds: currentTime }).catch(console.error);
@@ -1545,9 +2057,9 @@ export const usePlayerStore = create<PlayerState>()(
              const authStateCold = useAuthStore.getState();
              const replayGainDbCold = resolveReplayGainDb(
                currentTrack, coldPrev, coldNext,
-               authStateCold.replayGainEnabled, authStateCold.replayGainMode,
+               isReplayGainActive(), authStateCold.replayGainMode,
              );
-             const replayGainPeakCold = authStateCold.replayGainEnabled ? (currentTrack.replayGainPeak ?? null) : null;
+             const replayGainPeakCold = isReplayGainActive() ? (currentTrack.replayGainPeak ?? null) : null;
              const coldServerId = useAuthStore.getState().activeServerId ?? '';
              setDeferHotCachePrefetch(true);
              const coldUrl = resolvePlaybackUrl(currentTrack.id, coldServerId);
@@ -1558,10 +2070,12 @@ export const usePlayerStore = create<PlayerState>()(
                durationHint: currentTrack.duration,
                replayGainDb: replayGainDbCold,
                replayGainPeak: replayGainPeakCold,
+               loudnessGainDb: loudnessGainDbForEngineBind(currentTrack.id),
                preGainDb: authStateCold.replayGainPreGainDb,
                fallbackDb: authStateCold.replayGainFallbackDb,
                manual: false,
                hiResEnabled: useAuthStore.getState().enableHiRes,
+               analysisTrackId: currentTrack.id,
              }).catch((err: unknown) => {
                if (playGeneration !== gen) return;
                setDeferHotCachePrefetch(false);
@@ -1851,6 +2365,7 @@ export const usePlayerStore = create<PlayerState>()(
                 ...state.queue.slice(firstAutoIdx),
               ];
           syncQueueToServer(newQueue, state.currentTrack, state.currentTime);
+          prefetchLoudnessForEnqueuedTracks(tracks, newQueue, state.queueIndex);
           return { queue: newQueue };
         });
       },
@@ -1897,6 +2412,7 @@ export const usePlayerStore = create<PlayerState>()(
             ? state.queueIndex + tracks.length
             : state.queueIndex;
           syncQueueToServer(newQueue, state.currentTrack, state.currentTime);
+          prefetchLoudnessForEnqueuedTracks(tracks, newQueue, newQueueIndex);
           return { queue: newQueue, queueIndex: newQueueIndex };
         });
       },
@@ -1988,12 +2504,22 @@ export const usePlayerStore = create<PlayerState>()(
                currentTrack,
                currentTime: serverTime > 0 ? serverTime : localTime,
              });
+             void refreshWaveformForTrack(currentTrack.id);
            }
          } catch (e) {
            console.error('Failed to initialize queue from server', e);
          }
        },
 
+      reanalyzeLoudnessForTrack: async (trackId: string) => {
+        try {
+          showToast('Recalculating loudness for this track…', 2000, 'info');
+        } catch {
+          // no-op
+        }
+        await reseedLoudnessForTrackId(trackId);
+      },
+
        updateReplayGainForCurrentTrack: () => {
          const { currentTrack, queue, queueIndex, volume } = get();
          if (!currentTrack || !currentTrack.id) return;
@@ -2002,16 +2528,28 @@ export const usePlayerStore = create<PlayerState>()(
          const next = queueIndex + 1 < queue.length ? queue[queueIndex + 1] : null;
          const replayGainDb = resolveReplayGainDb(
            currentTrack, prev, next,
-           authState.replayGainEnabled, authState.replayGainMode,
+           isReplayGainActive(), authState.replayGainMode,
          );
-         const replayGainPeak = authState.replayGainEnabled
+         const replayGainPeak = isReplayGainActive()
            ? (currentTrack.replayGainPeak ?? null)
            : null;
          
-         invoke('audio_update_replay_gain', {
+        const normalization = deriveNormalizationSnapshot(currentTrack, queue, queueIndex);
+        const cachedLoud = cachedLoudnessGainByTrackId[currentTrack.id];
+        const cachedLoudDb = Number.isFinite(cachedLoud) ? cachedLoud : null;
+        set(prevState => ({
+          normalizationNowDb:
+            normalization.normalizationEngineLive === 'loudness'
+              ? (prevState.normalizationNowDb ?? cachedLoudDb)
+              : normalization.normalizationNowDb,
+          normalizationTargetLufs: normalization.normalizationTargetLufs,
+          normalizationEngineLive: normalization.normalizationEngineLive,
+        }));
+        invoke('audio_update_replay_gain', {
            volume,
            replayGainDb,
            replayGainPeak,
+           loudnessGainDb: currentTrack ? (cachedLoudnessGainByTrackId[currentTrack.id] ?? null) : null,
            preGainDb: authState.replayGainPreGainDb,
            fallbackDb: authState.replayGainFallbackDb,
          }).catch(console.error);

src/styles/layout.css

@@ -1989,6 +1989,24 @@ html[data-platform="windows"] .player-bar.floating {
   text-overflow: ellipsis;
 }
 
+.queue-current-tech-metric {
+  margin: 0;
+  padding: 0;
+  border: none;
+  background: transparent;
+  font: inherit;
+  letter-spacing: inherit;
+  line-height: inherit;
+  color: inherit;
+  cursor: pointer;
+  text-decoration: none;
+  border-radius: 2px;
+}
+
+.queue-current-tech-metric:hover {
+  background: color-mix(in srgb, var(--accent) 14%, transparent);
+}
+
 .queue-divider {
   padding: var(--space-3) var(--space-4) 0;
   flex-shrink: 0;