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Add timestamp iterator

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This commit is contained in:
David Payr
2024-12-28 23:46:47 +01:00
parent 792d9bd396
commit bffe0e60a6
9 changed files with 526 additions and 217 deletions
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src/isobmff/isobmff-demuxer.ts
+15 -20
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@@ -1305,18 +1305,12 @@ export class IsobmffDemuxer extends Demuxer {
abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudioChunk> implements InputTrackBacking {
chunkToSampleIndex = new WeakMap<Chunk, number>();
sampleIndexToChunk = new Map<number, WeakRef<Chunk>>();
chunkToFragmentLocation = new WeakMap<Chunk, {
fragment: Fragment;
sampleIndex: number;
}>();
fragmentLocationToChunk = new Map<string, WeakRef<Chunk>>();
constructor(public internalTrack: InternalTrack) {
}
constructor(public internalTrack: InternalTrack) {}
getCodec(): Promise<MediaCodec> {
throw new Error('Not implemented on base class.');
@@ -1355,7 +1349,20 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
return this.fetchChunkForSampleIndex(0, options);
}
private roundToMicrosecond(timestamp: number) {
// We transform the timestamp so that chunk retrieval behaves expectedly: All chunks returned have a timestamp
// that's floored to the microseconds, and that timestamp may be before the actual timestamp. But since the
// actual timestamp is never communicated to the outside, chunk retrieval should work like the timestamp is
// exactly equal to its floored version. This means, when we retrieve the chunk for timestamp 0.333333, but the
// chunk's true, unrounded timestamp is 1/3, then we would not retrieve that chunk, despite the chunk having a
// floored timestamp of 0.333333. That's why we transform the search timestamp by first flooring it to the
// microsecond, and then adding "1-eps" to it to make sure get all chunks whose timestamps will round down to
// a value included by the search timestamp.
return (Math.floor(timestamp * 1e6) + 0.99999999) / 1e6;
}
async getChunk(timestamp: number, options: ChunkRetrievalOptions) {
timestamp = this.roundToMicrosecond(timestamp);
const timestampInTimescale = timestamp * this.internalTrack.timescale;
if (this.internalTrack.demuxer.isFragmented) {
@@ -1441,6 +1448,7 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
}
async getKeyChunk(timestamp: number, options: ChunkRetrievalOptions) {
timestamp = this.roundToMicrosecond(timestamp);
const timestampInTimescale = timestamp * this.internalTrack.timescale;
if (this.internalTrack.demuxer.isFragmented) {
@@ -1545,11 +1553,6 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
return null;
}
const existingChunk = this.sampleIndexToChunk.get(sampleIndex)?.deref();
if (existingChunk) {
return existingChunk;
}
const sampleTable = this.internalTrack.demuxer.getSampleTableForTrack(this.internalTrack);
const sampleInfo = getSampleInfo(sampleTable, sampleIndex);
if (!sampleInfo) {
@@ -1577,7 +1580,6 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
const chunk = this.createChunk(data, timestamp, duration, sampleInfo.isKeyFrame);
this.chunkToSampleIndex.set(chunk, sampleIndex);
this.sampleIndexToChunk.set(sampleIndex, new WeakRef(chunk));
return chunk;
}
@@ -1587,12 +1589,6 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
return null;
}
const compositeKey = `${fragment.moofOffset}:${sampleIndex}`;
const existingChunk = this.fragmentLocationToChunk.get(compositeKey)?.deref();
if (existingChunk) {
return existingChunk;
}
const trackData = fragment.trackData.get(this.internalTrack.id)!;
const sample = trackData.samples[sampleIndex];
assert(sample);
@@ -1615,7 +1611,6 @@ abstract class IsobmffTrackBacking<Chunk extends EncodedVideoChunk | EncodedAudi
const chunk = this.createChunk(data, timestamp, duration, sample.isKeyFrame);
this.chunkToFragmentLocation.set(chunk, { fragment, sampleIndex });
this.fragmentLocationToChunk.set(compositeKey, new WeakRef(chunk));
return chunk;
}