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feat: parse mp4 webvtt segments#1545

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adrums86 merged 12 commits intomainfrom
feat-mp4-vtt
Oct 29, 2024
Merged

feat: parse mp4 webvtt segments#1545
adrums86 merged 12 commits intomainfrom
feat-mp4-vtt

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@adrums86 adrums86 commented Oct 11, 2024

Description

Feature

This pull request adds support for parsing mp4 encapsulated webvtt segments by modifying the existing vtt-segment-loader and associated functions to interface with the transmuxer to parse fmp4 webvtt initialization and content segments.

Specific Changes proposed

  • Update mux.js to include the WebVttParser for use in the transmuxer worker.
  • Modify the vtt-segment-loader to be able to handle fragmented mp4 segments.
  • Parse wvtt initialization segments and content segments with the help of the transmuxer.
  • Parse the cues provided by the transmuxer into VTTCue objects and add them to the subtitles text tracks.

Demo

See the deployed demo page here
with the simulated live DASH manifest from DASH-IF with mp4 encapsulated webvtt: https://livesim2.dashif.org/livesim2/timesubswvtt_en/testpic_2s/Manifest.mpd

Requirements Checklist

  • Feature implemented / Bug fixed
  • If necessary, more likely in a feature request than a bug fix
  • Reviewed by Two Core Contributors

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codecov Bot commented Oct 11, 2024

Codecov Report

Attention: Patch coverage is 98.11321% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.06%. Comparing base (8456cb3) to head (3618bdc).
Report is 1 commits behind head on main.

Files with missing lines Patch % Lines
src/transmuxer-worker.js 80.00% 1 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #1545      +/-   ##
==========================================
- Coverage   86.39%   84.06%   -2.34%     
==========================================
  Files          43       43              
  Lines       11165    11627     +462     
  Branches     2552     2604      +52     
==========================================
+ Hits         9646     9774     +128     
- Misses       1519     1853     +334     

☔ View full report in Codecov by Sentry.
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@adrums86 adrums86 marked this pull request as ready for review October 16, 2024 07:02
Comment thread src/vtt-segment-loader.js Outdated
}

const segmentInfo = this.pendingSegment_;
const isMp4WebVttSegment = result.mp4VttCues && result.mp4VttCues.length;
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minor but would isMp4WebVttSegmentWithCues be a more accurate name?

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Good call, much more descriptive.

Comment thread src/vtt-segment-loader.js
segmentInfo.mp4VttCues.forEach((cue) => {
const start = cue.start + timestampOffset;
const end = cue.end + timestampOffset;
const vttCue = new window.VTTCue(start, end, cue.cueText);
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@alex-barstow alex-barstow Oct 28, 2024

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Is it worth confirming the existence/data type of these cue values or are we guaranteed they will be correct at this point?

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The sample duration and cueText must be defined coming from the transmuxer, so I think we're guaranteed these values will be correct with regards to type at this point. https://github.com/videojs/mux.js/blob/e1b4d161f51782e4712d020b66d5087bd6febb3d/lib/mp4/webvtt-parser.js#L107

Comment thread src/vtt-segment-loader.js Outdated
Comment thread src/vtt-segment-loader.js Outdated
Comment thread src/transmuxer-worker.js
Comment thread src/transmuxer-worker.js
Comment thread src/media-segment-request.js
@adrums86 adrums86 merged commit 9f1c4ad into main Oct 29, 2024
@adrums86 adrums86 deleted the feat-mp4-vtt branch October 29, 2024 02:09
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4 participants