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fix: AC9 seek fine re-sync + deterministic decoder drain (WebCodecs Opus)

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Seek now trims the lead-in so playback lands at the requested time, not the page start; decoder drain polls decodeQueueSize (bounded) instead of a single timeout. Minor cleanups.
This commit is contained in:
daniel-c-harvey
2026-06-23 20:57:05 -04:00
parent 7f3fb74126
commit 5a75da1769
6 changed files with 186 additions and 42 deletions
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DeepDrftPublic/Interop/audio/AudioPlayer.ts
+16 -6
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@@ -16,7 +16,7 @@ import { WavFormatDecoder } from './WavFormatDecoder.js';
import { Mp3FormatDecoder } from './Mp3FormatDecoder.js';
import { FlacFormatDecoder } from './FlacFormatDecoder.js';
import { OpusStreamDecoder } from './OpusStreamDecoder.js';
import { OpusSeekData, parseSidecar, resolveOpusByteOffset } from './OpusSidecar.js';
import { OpusSeekData, parseSidecar, resolveOpusByteOffset, OpusSeekResolution } from './OpusSidecar.js';
export interface AudioResult {
success: boolean;
@@ -56,6 +56,10 @@ export class AudioPlayer {
// The sidecar in effect for the active Opus stream (its seek index resolves byte offsets). Distinct
// from pendingOpusSidecar, which is the one set for the NEXT stream init.
private activeOpusSidecar: OpusSeekData | null = null;
// The landing time of the most recent seek-beyond-buffer page resolution (seconds). Set by
// seekBeyondBuffer, consumed by reinitializeFromOffset to trim leading decoded frames so the
// audible position matches the requested seek target (AC9 fine re-sync, §3.4a step 4).
private _seekLandingTime: number = 0;
// Playback state
private isPlaying: boolean = false;
@@ -453,15 +457,19 @@ export class AudioPlayer {
try {
// Opus: resolve the offset from the precomputed seek index (the accurate VBR-safe transfer
// function). The returned offset is a real page start, so the Range continuation lands the
// demuxer/decoder Ogg-sync-aligned.
// demuxer/decoder Ogg-sync-aligned. Also capture the landing time (t_page ≤ position) so
// reinitializeFromOffset can trim the leading decoded frames and land precisely at `position`
// (AC9 fine re-sync, §3.4a step 4).
if (this.opusDecoder) {
if (!this.activeOpusSidecar) {
return { success: false, error: 'Cannot calculate byte offset' };
}
const resolution: OpusSeekResolution = resolveOpusByteOffset(this.activeOpusSidecar, position);
this._seekLandingTime = resolution.landingTimeSeconds;
return {
success: true,
seekBeyondBuffer: true,
byteOffset: resolveOpusByteOffset(this.activeOpusSidecar, position)
byteOffset: resolution.byteOffset
};
}
@@ -499,7 +507,7 @@ export class AudioPlayer {
calculateByteOffset(positionSeconds: number): number {
if (this.opusDecoder) {
return this.activeOpusSidecar
? resolveOpusByteOffset(this.activeOpusSidecar, positionSeconds)
? resolveOpusByteOffset(this.activeOpusSidecar, positionSeconds).byteOffset
: 0;
}
if (!this.streamDecoder.getFormatInfo()) return 0;
@@ -521,10 +529,11 @@ export class AudioPlayer {
this.scheduler.setPlaybackOffset(seekPosition);
// Reinitialize the active decoder for the Range-continuation stream (206 body, no header/
// setup pages). Opus resets demux + codec state (keeping the cached config); the
// setup pages). Opus resets demux + codec state (keeping the cached config) and arms the
// lead-trim so decoded audio starts at `seekPosition`, not at the page boundary (AC9). The
// StreamDecoder path uses totalStreamLength (the 206 Content-Length) to detect completion.
if (this.opusDecoder) {
this.opusDecoder.reinitializeForRangeContinuation();
this.opusDecoder.reinitializeForRangeContinuation(this._seekLandingTime, seekPosition);
} else {
this.streamDecoder.reinitializeForRangeContinuation(totalStreamLength);
}
@@ -643,6 +652,7 @@ export class AudioPlayer {
this.isStreamingMode = false;
this.streamingStarted = false;
this.streamingCompleted = false;
this._seekLandingTime = 0;
}
private handlePlaybackEnded(): void {