fix: reset fragmentation state on seek to prevent invalid fragment ranges

src/isofile.ts

@@ -1073,6 +1073,8 @@ export class ISOFile<TSegmentUser = unknown, TSampleUser = unknown> {
     }
     time = trak.samples[seek_sample_num].cts;
     trak.nextSample = seek_sample_num;
+    this.resetFragmentedTrackStateAfterSeek(trak, seek_sample_num);
+    this.resetExtractedTrackStateAfterSeek(trak);
     while (trak.samples[seek_sample_num].alreadyRead === trak.samples[seek_sample_num].size) {
       // No remaining samples to look for, all are downloaded.
       if (!trak.samples[seek_sample_num + 1]) {
@@ -1098,6 +1100,27 @@ export class ISOFile<TSegmentUser = unknown, TSampleUser = unknown> {
     return { offset: seek_offset, time: time / timescale };
   }
 
+  resetFragmentedTrackStateAfterSeek(trak: trakBox, seekSampleNumber: number) {
+    const fragTrack = this.fragmentedTracks.find(t => t.trak === trak);
+    if (!fragTrack) {
+      return;
+    }
+
+    fragTrack.state.lastFragmentSampleNumber = seekSampleNumber;
+    fragTrack.state.lastSegmentSampleNumber = seekSampleNumber;
+    fragTrack.state.accumulatedSize = 0;
+    fragTrack.segmentStream = undefined;
+  }
+
+  resetExtractedTrackStateAfterSeek(trak: trakBox) {
+    const extractTrack = this.extractedTracks.find(t => t.trak === trak);
+    if (!extractTrack) {
+      return;
+    }
+
+    extractTrack.samples = [];
+  }
+
   getTrackDuration(trak: trakBox) {
     if (!trak.samples) {
       return Infinity;
@@ -1182,6 +1205,14 @@ export class ISOFile<TSegmentUser = unknown, TSampleUser = unknown> {
     sampleEnd: number,
     existingStream: DataStream,
   ) {
+    if (sampleEnd < sampleStart) {
+      Log.warn(
+        'ISOFile',
+        `Skipping fragment creation on track #${track_id}: invalid sample range [${sampleStart}, ${sampleEnd}]`,
+      );
+      return existingStream || new DataStream();
+    }
+
     // Check existence of all samples
     const samples: Array<Sample> = [];
     for (let i = sampleStart; i <= sampleEnd; i++) {

tests/segmentation.test.ts

@@ -206,4 +206,89 @@ describe('File Segmentation', () => {
     expect(newMP4.getBoxes('moof', false).length).toBe(10);
     expect(out.getAbsoluteEndPosition()).toBe(203_175);
   });
+
+  it('resets segmentation state on seek', async () => {
+    const { testFile } = getFilePath('isobmff', '01_simple.mp4');
+    const { mp4 } = await loadAndGetInfo(testFile, true, true);
+
+    mp4.setSegmentOptions(201, undefined, {
+      nbSamples: 100,
+      nbSamplesPerFragment: 50,
+      rapAlignement: false,
+    });
+    mp4.initializeSegmentation();
+    mp4.onSegment = () => undefined;
+
+    mp4.start();
+
+    const fragTrack = mp4.fragmentedTracks.find(track => track.id === 201);
+    expect(fragTrack).toBeDefined();
+    if (!fragTrack) {
+      throw new Error('Missing fragmented track #201');
+    }
+
+    mp4.seek(0, false);
+
+    expect(fragTrack.state.lastFragmentSampleNumber).toBe(fragTrack.trak.nextSample);
+    expect(fragTrack.state.lastSegmentSampleNumber).toBe(fragTrack.trak.nextSample);
+    expect(fragTrack.state.accumulatedSize).toBe(0);
+    expect(fragTrack.segmentStream).toBeUndefined();
+    expect(() => mp4.start()).not.toThrow();
+  });
+
+  it('resets segmentation state on forward seek before processing', async () => {
+    const { testFile } = getFilePath('isobmff', '01_simple.mp4');
+    const { mp4 } = await loadAndGetInfo(testFile, true, true);
+
+    mp4.setSegmentOptions(201, undefined, {
+      nbSamples: 100,
+      nbSamplesPerFragment: 50,
+      rapAlignement: false,
+    });
+    mp4.initializeSegmentation();
+
+    const fragTrack = mp4.fragmentedTracks.find(track => track.id === 201);
+    expect(fragTrack).toBeDefined();
+    if (!fragTrack) {
+      throw new Error('Missing fragmented track #201');
+    }
+
+    mp4.seek(3, false);
+
+    expect(fragTrack.trak.nextSample).toBeGreaterThan(0);
+    expect(fragTrack.state.lastFragmentSampleNumber).toBe(fragTrack.trak.nextSample);
+    expect(fragTrack.state.lastSegmentSampleNumber).toBe(fragTrack.trak.nextSample);
+    expect(fragTrack.state.accumulatedSize).toBe(0);
+    expect(fragTrack.segmentStream).toBeUndefined();
+  });
+
+  it('resets segmentation state on backward seek after a forward seek', async () => {
+    const { testFile } = getFilePath('isobmff', '01_simple.mp4');
+    const { mp4 } = await loadAndGetInfo(testFile, true, true);
+
+    mp4.setSegmentOptions(201, undefined, {
+      nbSamples: 100,
+      nbSamplesPerFragment: 50,
+      rapAlignement: false,
+    });
+    mp4.initializeSegmentation();
+
+    const fragTrack = mp4.fragmentedTracks.find(track => track.id === 201);
+    expect(fragTrack).toBeDefined();
+    if (!fragTrack) {
+      throw new Error('Missing fragmented track #201');
+    }
+
+    mp4.seek(3, false);
+    const forwardSample = fragTrack.trak.nextSample;
+    expect(forwardSample).toBeGreaterThan(0);
+
+    mp4.seek(0, false);
+
+    expect(fragTrack.trak.nextSample).toBeLessThan(forwardSample);
+    expect(fragTrack.state.lastFragmentSampleNumber).toBe(fragTrack.trak.nextSample);
+    expect(fragTrack.state.lastSegmentSampleNumber).toBe(fragTrack.trak.nextSample);
+    expect(fragTrack.state.accumulatedSize).toBe(0);
+    expect(fragTrack.segmentStream).toBeUndefined();
+  });
 });