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fix(HLS): Fix duplicate hinted segments (shaka-project#4258)
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Because zero-duration references cause such chaos, ensure that the HLS
parser never produces these.  Preload-hinted segments should use the
target duration for partial segments, and if that required attribute
is missing from the playlist, then preload-hinted segments should be
skipped.

Closes shaka-project#4223
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@joeyparrish @theodab
joeyparrish authored and theodab committed Jun 3, 2022
1 parent d84edfe commit 52949c2
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Showing 2 changed files with 71 additions and 10 deletions.
17 changes: 14 additions & 3 deletions lib/hls/hls_parser.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1893,9 +1893,20 @@ shaka.hls.HlsParser = class {
const pPreviousReference = i == 0 ?
previousReference : partialSegmentRefs[partialSegmentRefs.length - 1];
const pStartTime = (i == 0) ? startTime : pPreviousReference.endTime;
const pDuration = Number(item.getAttributeValue('DURATION'));
// A preload hinted partial segment doesn't have duration information,
// so its startTime and endTime are the same.

// If DURATION is missing from this partial segment, use the target
// partial duration from the top of the playlist, which is a required
// attribute for content with partial segments.
const pDuration = Number(item.getAttributeValue('DURATION')) ||
this.partialTargetDuration_;

// If for some reason we have neither an explicit duration, nor a target
// partial duration, we should SKIP this partial segment to avoid
// duplicating content in the presentation timeline.
if (!pDuration) {
continue;
}

const pEndTime = pStartTime + pDuration;

let pStartByte = 0;
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64 changes: 57 additions & 7 deletions test/hls/hls_live_unit.js
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Original file line number Diff line number Diff line change
Expand Up @@ -539,11 +539,13 @@ describe('HlsParser live', () => {
ManifestParser.verifySegmentIndex(video, [ref1, ref2]);
});

// Test for https://github.com/shaka-project/shaka-player/issues/4223
it('parses streams with partial and preload hinted segments', async () => {
playerInterface.isLowLatencyMode = () => true;
const mediaWithPartialSegments = [
'#EXTM3U\n',
'#EXT-X-TARGETDURATION:5\n',
'#EXT-X-PART-INF:PART-TARGET=1.5\n',
'#EXT-X-MAP:URI="init.mp4",BYTERANGE="616@0"\n',
'#EXT-X-MEDIA-SEQUENCE:0\n',
// ref includes partialRef, partialRef2
Expand Down Expand Up @@ -576,26 +578,73 @@ describe('HlsParser live', () => {
'test:/partial2.mp4', 2, 4, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 200, /* endByte= */ 429);

const ref = makeReference(
'test:/main.mp4', 0, 4, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ 429,
/* timestampOffset= */ 0, [partialRef, partialRef2]);

const partialRef3 = makeReference(
'test:/partial.mp4', 4, 6, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ 209);

// A preload hinted partial segment doesn't have duration information,
// so its startTime and endTime are the same.
const preloadRef = makeReference(
'test:/partial.mp4', 6, 6, /* syncTime= */ null,
'test:/partial.mp4', 6, 7.5, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 210, /* endByte= */ null);

// ref2 is not fully published yet, so it doesn't have a segment uri.
const ref2 = makeReference(
'', 4, 7.5, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ null,
/* timestampOffset= */ 0, [partialRef3, preloadRef]);

const manifest = await parser.start('test:/master', playerInterface);
const video = manifest.variants[0].video;
await video.createSegmentIndex();
ManifestParser.verifySegmentIndex(video, [ref, ref2]);
});

// Test for https://github.com/shaka-project/shaka-player/issues/4223
it('ignores preload hinted segments without target duration', async () => {
playerInterface.isLowLatencyMode = () => true;

// Missing PART-TARGET, so preload hints are skipped.
const mediaWithPartialSegments = [
'#EXTM3U\n',
'#EXT-X-TARGETDURATION:5\n',
'#EXT-X-MAP:URI="init.mp4",BYTERANGE="616@0"\n',
'#EXT-X-MEDIA-SEQUENCE:0\n',
'#EXTINF:4,\n',
// ref1
'main.mp4\n',
// ref2 includes partialRef, but not preloadRef
// partialRef
'#EXT-X-PART:DURATION=2,URI="partial.mp4",BYTERANGE=210@0\n',
// preloadRef
'#EXT-X-PRELOAD-HINT:TYPE=PART,URI="partial.mp4",BYTERANGE-START=210\n',
].join('');

fakeNetEngine
.setResponseText('test:/master', master)
.setResponseText('test:/video', mediaWithPartialSegments)
.setResponseValue('test:/init.mp4', initSegmentData)
.setResponseValue('test:/main.mp4', segmentData)
.setResponseValue('test:/partial.mp4', segmentData)
.setResponseValue('test:/partial2.mp4', segmentData);

const ref = makeReference(
'test:/main.mp4', 0, 4, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ 429,
/* timestampOffset= */ 0, [partialRef, partialRef2]);
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ null,
/* timestampOffset= */ 0, []);

const partialRef = makeReference(
'test:/partial.mp4', 4, 6, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ 209);

// ref2 is not fully published yet, so it doesn't have a segment uri.
const ref2 = makeReference(
'', 4, 6, /* syncTime= */ null,
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ null,
/* timestampOffset= */ 0, [partialRef3, preloadRef]);
/* baseUri= */ '', /* startByte= */ 0, /* endByte= */ 209,
/* timestampOffset= */ 0, [partialRef]);

const manifest = await parser.start('test:/master', playerInterface);
const video = manifest.variants[0].video;
Expand All @@ -611,6 +660,7 @@ describe('HlsParser live', () => {
const mediaWithPartialSegments = [
'#EXTM3U\n',
'#EXT-X-TARGETDURATION:5\n',
'#EXT-X-PART-INF:PART-TARGET=1.5\n',
'#EXTINF:4,\n',
'main.mp4\n',
'#EXT-X-PART:DURATION=2,URI="partial.mp4",BYTERANGE=210@0\n',
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