feat(playback): global speed with three strategies (#852)

* feat(playback): global speed with three strategies

Add Settings → Audio and player-bar controls for global playback speed
(speed with auto pitch correction as default, varispeed, manual pitch shift).
Time-stretch runs on a background worker; Orbit sessions force 1.0× passthrough.

* fix(playback): align seekbar, seek, and progress on content timeline

Unify UI timebase across varispeed and preserve strategies: full-track
duration, speed-scaled progress for DSP paths, and content-timeline seeks
without varispeed scaling. Reset the sample counter after seek so clicks
land correctly; restart playback on strategy/enable changes instead of
fragile hot-switching.

* fix(ui): anchor playback speed popover like volume controls

Replace the centered EQ-style modal with a player-bar popover (outside
click, Escape, reposition on scroll). Show compact controls in the bar
and overflow menu; keep strategy hints and labels in Settings only.

* docs(release): CHANGELOG and credits for playback speed (PR #852)

* docs(changelog): add playback speed entry for PR #852

* fix(clippy): simplify raw_counter_samples branch for CI

Collapse duplicate if branches flagged by clippy::if-same-then-else.

* fix(ui): wheel on pitch slider adjusts pitch in speed popover

In compact player-bar controls, scroll over the pitch row changes pitch;
elsewhere in the panel changes speed. Stop propagation so overflow menu
wheel does not tweak volume.

* fix(playback): address PR #852 review and drop ineffective dynamic imports

Translate playback-rate strings for de/fr/es/zh/nb/nl/ro; restamp sample
counter on live preserve-path speed changes; use neutral rate atomics for
radio progress; static-import playerStore in playListenSession (move preview
volume sync to previewPlayerVolumeSync side-effect module).

* fix(i18n): translate playback-rate strategy labels in all locales

Replace leftover English Varispeed/Pitch strings in ru and other non-en
settings blocks so popover strategy buttons and hints read natively.

* fix(i18n): refine German varispeed label to "Tonhöhe folgt dem Tempo"

---------

Co-authored-by: Psychotoxical <171614930+Psychotoxical@users.noreply.github.com>

src/utils/audio/playbackRateHelpers.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from 'vitest';
+import {
+  clampPlaybackSpeed,
+  isPlaybackEffectActive,
+  isPlaybackRateApplied,
+  derivedVarispeedSemitones,
+} from './playbackRateHelpers';
+
+describe('playbackRateHelpers', () => {
+  it('is inactive when disabled', () => {
+    expect(isPlaybackEffectActive(false, 'speed_corrected', 1.5, 0)).toBe(false);
+  });
+
+  it('is inactive at 1.0x and 0 pitch when enabled', () => {
+    expect(isPlaybackEffectActive(true, 'speed_corrected', 1.0, 0)).toBe(false);
+  });
+
+  it('is active when speed differs from 1', () => {
+    expect(isPlaybackEffectActive(true, 'speed_corrected', 1.25, 0)).toBe(true);
+  });
+
+  it('preserve_pitch is active at 1.0x with pitch offset', () => {
+    expect(isPlaybackEffectActive(true, 'preserve_pitch', 1.0, 2)).toBe(true);
+  });
+
+  it('speed_corrected ignores stored pitch at 1.0x', () => {
+    expect(isPlaybackEffectActive(true, 'speed_corrected', 1.0, 2)).toBe(false);
+  });
+
+  it('clamps speed', () => {
+    expect(clampPlaybackSpeed(3)).toBe(2);
+    expect(clampPlaybackSpeed(0.1)).toBe(0.5);
+  });
+
+  it('derives semitones for varispeed', () => {
+    expect(derivedVarispeedSemitones(2)).toBeCloseTo(12, 1);
+  });
+
+  it('is not applied during orbit', () => {
+    expect(isPlaybackRateApplied(true, 'speed_corrected', 1.5, 0, true)).toBe(false);
+    expect(isPlaybackRateApplied(true, 'speed_corrected', 1.5, 0, false)).toBe(true);
+  });
+});

src/utils/audio/playbackRateHelpers.ts

@@ -0,0 +1,74 @@
+export type PlaybackStrategy = 'speed_corrected' | 'varispeed' | 'preserve_pitch';
+
+/** Default strategy: speed only, pitch corrected automatically. */
+export const DEFAULT_PLAYBACK_STRATEGY: PlaybackStrategy = 'speed_corrected';
+
+export const PLAYBACK_STRATEGIES: PlaybackStrategy[] = [
+  'speed_corrected',
+  'varispeed',
+  'preserve_pitch',
+];
+
+export const PLAYBACK_SPEED_MIN = 0.5;
+export const PLAYBACK_SPEED_MAX = 2.0;
+export const PLAYBACK_SPEED_STEP = 0.05;
+export const PLAYBACK_PITCH_MIN = -12;
+export const PLAYBACK_PITCH_MAX = 12;
+export const PLAYBACK_PITCH_STEP = 0.1;
+export const PLAYBACK_SPEED_PRESETS = [0.75, 1.0, 1.25, 1.5, 2.0] as const;
+
+export function clampPlaybackSpeed(speed: number): number {
+  return Math.max(PLAYBACK_SPEED_MIN, Math.min(PLAYBACK_SPEED_MAX, speed));
+}
+
+export function clampPlaybackPitch(semitones: number): number {
+  return Math.max(PLAYBACK_PITCH_MIN, Math.min(PLAYBACK_PITCH_MAX, semitones));
+}
+
+/** Pitch sent to Rust: manual offset only in preserve_pitch strategy. */
+export function effectivePlaybackPitch(
+  strategy: PlaybackStrategy,
+  pitchSemitones: number,
+): number {
+  return strategy === 'preserve_pitch' ? pitchSemitones : 0;
+}
+
+/** True when DSP should run (enabled + not neutral 1.0× / 0 st). */
+export function isPlaybackEffectActive(
+  enabled: boolean,
+  strategy: PlaybackStrategy,
+  speed: number,
+  pitchSemitones: number,
+): boolean {
+  if (!enabled) return false;
+  if (strategy === 'preserve_pitch') {
+    return Math.abs(speed - 1) > 0.001 || Math.abs(pitchSemitones) > 0.001;
+  }
+  return Math.abs(speed - 1) > 0.001;
+}
+
+/** True when the engine applies playback-rate DSP (Orbit sessions force passthrough). */
+export function isPlaybackRateApplied(
+  enabled: boolean,
+  strategy: PlaybackStrategy,
+  speed: number,
+  pitchSemitones: number,
+  orbitSessionActive: boolean,
+): boolean {
+  if (orbitSessionActive) return false;
+  return isPlaybackEffectActive(enabled, strategy, speed, pitchSemitones);
+}
+
+export function derivedVarispeedSemitones(speed: number): number {
+  if (speed <= 0) return 0;
+  return 12 * Math.log2(speed);
+}
+
+export function formatSpeedLabel(speed: number): string {
+  return `${speed.toFixed(1)}×`;
+}
+
+export function formatPitchLabel(semitones: number): string {
+  const rounded = Math.round(semitones * 10) / 10;
+  return rounded > 0 ? `+${rounded.toFixed(1)} st` : `${rounded.toFixed(1)} st`;
+}

src/utils/audio/playbackRateRestart.test.ts

@@ -0,0 +1,54 @@
+import { describe, expect, it } from 'vitest';
+import { isPlaybackEffectActive } from './playbackRateHelpers';
+import {
+  playbackPathChanged,
+  shouldRestartPlaybackForRateChange,
+  usesPreservePlaybackPath,
+} from './playbackRateRestart';
+
+describe('playbackRateRestart', () => {
+  const base = {
+    enabled: true,
+    strategy: 'speed_corrected' as const,
+    speed: 1.5,
+    pitchSemitones: 0,
+  };
+
+  it('detects preserve vs varispeed paths', () => {
+    expect(usesPreservePlaybackPath('speed_corrected')).toBe(true);
+    expect(usesPreservePlaybackPath('preserve_pitch')).toBe(true);
+    expect(usesPreservePlaybackPath('varispeed')).toBe(false);
+    expect(playbackPathChanged('speed_corrected', 'varispeed')).toBe(true);
+    expect(playbackPathChanged('speed_corrected', 'preserve_pitch')).toBe(false);
+  });
+
+  it('restarts on strategy change', () => {
+    expect(shouldRestartPlaybackForRateChange(
+      base,
+      { ...base, strategy: 'varispeed' },
+    )).toBe(true);
+  });
+
+  it('restarts when effect becomes active', () => {
+    expect(shouldRestartPlaybackForRateChange(
+      { ...base, speed: 1.0 },
+      { ...base, speed: 1.5 },
+    )).toBe(true);
+    expect(isPlaybackEffectActive(true, 'speed_corrected', 1.0, 0)).toBe(false);
+    expect(isPlaybackEffectActive(true, 'speed_corrected', 1.5, 0)).toBe(true);
+  });
+
+  it('does not restart on speed tweak within varispeed', () => {
+    expect(shouldRestartPlaybackForRateChange(
+      { ...base, strategy: 'varispeed', speed: 1.5 },
+      { ...base, strategy: 'varispeed', speed: 1.75 },
+    )).toBe(false);
+  });
+
+  it('does not restart on pitch tweak within preserve_pitch', () => {
+    expect(shouldRestartPlaybackForRateChange(
+      { ...base, strategy: 'preserve_pitch', pitchSemitones: 0 },
+      { ...base, strategy: 'preserve_pitch', pitchSemitones: 2 },
+    )).toBe(false);
+  });
+});

src/utils/audio/playbackRateRestart.ts

@@ -0,0 +1,70 @@
+import { usePlayerStore } from '../../store/playerStore';
+import { setSeekFallbackVisualTarget } from '../../store/seekFallbackState';
+import { isPlaybackEffectActive, type PlaybackStrategy } from './playbackRateHelpers';
+
+/** Preserve-pitch DSP (worker) vs direct varispeed sample-rate scaling. */
+export function usesPreservePlaybackPath(strategy: PlaybackStrategy): boolean {
+  return strategy === 'speed_corrected' || strategy === 'preserve_pitch';
+}
+
+export function playbackPathChanged(a: PlaybackStrategy, b: PlaybackStrategy): boolean {
+  return usesPreservePlaybackPath(a) !== usesPreservePlaybackPath(b);
+}
+
+export interface PlaybackRateSnapshot {
+  enabled: boolean;
+  strategy: PlaybackStrategy;
+  speed: number;
+  pitchSemitones: number;
+}
+
+/** Whether live atomics are enough vs needing a source rebuild (spec §2.5). */
+export function shouldRestartPlaybackForRateChange(
+  prev: PlaybackRateSnapshot,
+  next: PlaybackRateSnapshot,
+): boolean {
+  if (prev.strategy !== next.strategy) return true;
+  if (prev.enabled !== next.enabled && isPlaybackEffectActive(
+    next.enabled,
+    next.strategy,
+    next.speed,
+    next.pitchSemitones,
+  )) {
+    return true;
+  }
+  const prevActive = isPlaybackEffectActive(
+    prev.enabled,
+    prev.strategy,
+    prev.speed,
+    prev.pitchSemitones,
+  );
+  const nextActive = isPlaybackEffectActive(
+    next.enabled,
+    next.strategy,
+    next.speed,
+    next.pitchSemitones,
+  );
+  if (prevActive !== nextActive) return true;
+  return false;
+}
+
+/** Re-decode current track at the current timeline position (seek-restart). */
+export function restartPlaybackForRateChange(): void {
+  const player = usePlayerStore.getState();
+  const track = player.currentTrack;
+  if (!track || !player.isPlaying) return;
+  if (track.radioAdded) return;
+
+  const dur = track.duration;
+  if (!dur || !Number.isFinite(dur) || dur <= 0) return;
+
+  const time = Math.max(0, Math.min(player.currentTime, dur - 0.25));
+  if (time > 0.05) {
+    setSeekFallbackVisualTarget({
+      trackId: track.id,
+      seconds: time,
+      setAtMs: Date.now(),
+    });
+  }
+  player.playTrack(track, player.queue, true);
+}

src/utils/orbit.ts

@@ -31,6 +31,7 @@ export {
   serialiseOrbitState,
   suggestionKey,
 } from './orbit/helpers';
+export { isOrbitPlaybackSyncActive } from './orbit/sessionActive';
 export {
   applyOutboxSnapshotsToState,
   computeOrbitDriftMs,

src/utils/orbit/sessionActive.ts

@@ -0,0 +1,14 @@
+import type { OrbitPhase, OrbitRole } from '../../store/orbitStore';
+import { useOrbitStore } from '../../store/orbitStore';
+
+/**
+ * True while this client is in an Orbit session on the shared playback path
+ * (host/guest during start, join, or active play). Matches previewStore guard.
+ */
+export function isOrbitPlaybackSyncActive(
+  role: OrbitRole | null = useOrbitStore.getState().role,
+  phase: OrbitPhase = useOrbitStore.getState().phase,
+): boolean {
+  if (role !== 'host' && role !== 'guest') return false;
+  return phase === 'active' || phase === 'joining' || phase === 'starting';
+}