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Improve lookup algorithm to handle misleading cue points, fix cluster start timestamp in Matroska muxer, improve cue points in Matroska muxer, & other misc improvements

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Vanilagy
2025-01-12 15:17:21 +01:00
parent 61a4f1483a
commit 2dfb595911
7 changed files with 216 additions and 93 deletions
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src/isobmff/isobmff-demuxer.ts
+25 -20
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@@ -1792,6 +1792,7 @@ abstract class IsobmffTrackBacking<
x => x.moofOffset,
);
assert(fragmentIndex !== -1);
return {
fragmentIndex,
sampleIndex: 0,
@@ -2053,15 +2054,11 @@ abstract class IsobmffTrackBacking<
/** Looks for a sample in the fragments while trying to load as few fragments as possible to retrieve it. */
private async performFragmentedLookup(
// This function returns the best-matching sample that is currently loaded. Based on this information, we know
// which fragments we need to load to find the actual match.
getBestMatch: () => { fragmentIndex: number; sampleIndex: number; correctSampleFound: boolean },
// The timestamp with which we can search the lookup table
searchTimestamp: number,
// The timestamp for which we know the correct sample will not come after it
latestTimestamp: number,
options: SampleRetrievalOptions,
) {
): Promise<Sample | null> {
const demuxer = this.internalTrack.demuxer;
const release = await demuxer.fragmentLookupMutex.acquire(); // The algorithm requires exclusivity
@@ -2080,20 +2077,18 @@ abstract class IsobmffTrackBacking<
let bestFragmentIndex = fragmentIndex;
let bestSampleIndex = sampleIndex;
let lookupEntry: FragmentLookupTableEntry | null = null;
if (this.internalTrack.fragmentLookupTable) {
// Search for a lookup entry; this way, we won't need to start searching from the start of the file
// but can jump right into the correct fragment (or at least nearby).
const index = binarySearchLessOrEqual(
// Search for a lookup entry; this way, we won't need to start searching from the start of the file
// but can jump right into the correct fragment (or at least nearby).
const lookupEntryIndex = this.internalTrack.fragmentLookupTable
? binarySearchLessOrEqual(
this.internalTrack.fragmentLookupTable,
searchTimestamp,
x => x.timestamp,
);
if (index !== -1) {
lookupEntry = this.internalTrack.fragmentLookupTable[index]!;
}
}
)
: -1;
const lookupEntry = lookupEntryIndex !== -1
? this.internalTrack.fragmentLookupTable![lookupEntryIndex]!
: null;
if (fragmentIndex === -1) {
isobmffReader.pos = lookupEntry?.moofOffset ?? 0;
@@ -2163,13 +2158,23 @@ abstract class IsobmffTrackBacking<
isobmffReader.pos = startPos + boxInfo.totalSize;
}
if (bestFragmentIndex !== -1) {
let result: Sample | null = null;
const bestFragment = bestFragmentIndex !== -1 ? this.internalTrack.fragments[bestFragmentIndex]! : null;
if (bestFragment) {
// If we finished looping but didn't find a perfect match, still return the best match we found
const fragment = this.internalTrack.fragments[bestFragmentIndex]!;
return this.fetchSampleInFragment(fragment, bestSampleIndex, options);
result = await this.fetchSampleInFragment(bestFragment, bestSampleIndex, options);
}
return null;
// Catch faulty lookup table entries
if (!result && lookupEntry && (!bestFragment || bestFragment.moofOffset < lookupEntry.moofOffset)) {
// The lookup table entry lied to us! We found a lookup entry but no fragment there that satisfied
// the match. In this case, let's search again but using the lookup entry before that.
const previousLookupEntry = this.internalTrack.fragmentLookupTable![lookupEntryIndex - 1];
const newSearchTimestamp = previousLookupEntry?.timestamp ?? -Infinity;
return this.performFragmentedLookup(getBestMatch, newSearchTimestamp, latestTimestamp, options);
}
return result;
} finally {
release();
}