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Terminate reading a cluster early if another cluster is encountered (fixes #164)

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This commit is contained in:
Vanilagy
2025-10-21 16:18:48 +02:00
parent 0c4c13cea2
commit e676de4129
1 changed files with 42 additions and 37 deletions
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src/matroska/matroska-demuxer.ts
+42 -37
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@@ -637,7 +637,10 @@ export class MatroskaDemuxer extends Demuxer {
this.currentCluster = cluster;
if (dataSlice) {
this.readContiguousElements(dataSlice);
// Read the children of the cluster, stopping early at level 0 or 1 EBML elements. We do this because some
// clusters have incorrect sizes that are too large
const endPos = this.readContiguousElements(dataSlice, LEVEL_0_AND_1_EBML_IDS);
cluster.elementEndPos = endPos;
}
for (const [, trackData] of cluster.trackData) {
@@ -913,24 +916,31 @@ export class MatroskaDemuxer extends Demuxer {
}
}
readContiguousElements(slice: FileSlice) {
readContiguousElements(slice: FileSlice, stopIds?: number[]) {
const startIndex = slice.filePos;
while (slice.filePos - startIndex <= slice.length - MIN_HEADER_SIZE) {
const foundElement = this.traverseElement(slice);
const startPos = slice.filePos;
const foundElement = this.traverseElement(slice, stopIds);
if (!foundElement) {
break;
return startPos;
}
}
return slice.filePos;
}
traverseElement(slice: FileSlice): boolean {
traverseElement(slice: FileSlice, stopIds?: number[]): boolean {
const header = readElementHeader(slice);
if (!header) {
return false;
}
if (stopIds && stopIds.includes(header.id)) {
return false;
}
const { id, size } = header;
const dataStartPos = slice.filePos;
assertDefinedSize(size);
@@ -2174,6 +2184,8 @@ abstract class MatroskaTrackBacking implements InputTrackBacking {
if (id === EBMLId.Cluster) {
currentCluster = await demuxer.readCluster(elementStartPos, segment);
// readCluster computes the proper size even if it's undefined in the header, so let's use that instead
size = currentCluster.elementEndPos - dataStartPos;
const { blockIndex, correctBlockFound } = getMatchInCluster(currentCluster);
if (correctBlockFound) {
@@ -2190,44 +2202,37 @@ abstract class MatroskaTrackBacking implements InputTrackBacking {
// Undefined element size (can happen in livestreamed files). In this case, we need to do some
// searching to determine the actual size of the element.
if (id === EBMLId.Cluster) {
// The cluster should have already computed its length, we can just copy that result
assert(currentCluster);
size = currentCluster.elementEndPos - dataStartPos;
} else {
// Search for the next element at level 0 or 1
const nextElementPos = await searchForNextElementId(
demuxer.reader,
dataStartPos,
LEVEL_0_AND_1_EBML_IDS,
segment.elementEndPos,
);
assert(id !== EBMLId.Cluster); // Undefined cluster sizes are fixed further up
size = nextElementPos.pos - dataStartPos;
}
// Search for the next element at level 0 or 1
const nextElementPos = await searchForNextElementId(
demuxer.reader,
dataStartPos,
LEVEL_0_AND_1_EBML_IDS,
segment.elementEndPos,
);
const endPos = dataStartPos + size;
if (segment.elementEndPos !== null && endPos > segment.elementEndPos - MIN_HEADER_SIZE) {
// No more elements fit in this segment
size = nextElementPos.pos - dataStartPos;
}
const endPos = dataStartPos + size;
if (segment.elementEndPos === null) {
// Check the next element. If it's a new segment, we know this segment ends here. The new
// segment is just ignored, since we're likely in a livestreamed file and thus only care about
// the first segment.
let slice = demuxer.reader.requestSliceRange(endPos, MIN_HEADER_SIZE, MAX_HEADER_SIZE);
if (slice instanceof Promise) slice = await slice;
if (!slice) break;
const elementId = readElementId(slice);
if (elementId === EBMLId.Segment) {
segment.elementEndPos = endPos; // We now know the segment's size
break;
} else {
// Check the next element. If it's a new segment, we know this segment ends here. The new
// segment is just ignored, since we're likely in a livestreamed file and thus only care about
// the first segment.
let slice = demuxer.reader.requestSliceRange(endPos, MIN_HEADER_SIZE, MAX_HEADER_SIZE);
if (slice instanceof Promise) slice = await slice;
if (!slice) break;
const elementId = readElementId(slice);
if (elementId === EBMLId.Segment) {
segment.elementEndPos = endPos;
break;
}
}
}
currentPos = dataStartPos + size;
currentPos = endPos;
}
// Catch faulty cue points