Fix for Opus audio in fragmented MP4 #1219
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The Opus box name is capitalized, but MediaSource expects a lowercase "opus" codec string, which was causing unexpected failures in Chrome and Firefox. Now matches behavior of mux.js for audio tracks by forcing the box type to lowercase before returning it as a codec string.
| @@ -440,7 +440,8 @@ const handleSegmentBytes = ({ | |||
| // if we have a audio track, with a codec that is not set to | |||
| // encrypted audio | |||
| if (tracks.audio && tracks.audio.codec && tracks.audio.codec !== 'enca') { | |||
| trackInfo.audioCodec = tracks.audio.codec; | |||
| // note Opus box name is capitalized, but things want lowercase for checks | |||
| trackInfo.audioCodec = tracks.audio.codec.toLowerCase(); | |||
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We get this information from mux.js specifically lib/mp4/probe.js and we toLowerCase the codec there if it isn't one that we know. I guess i'm just not understanding how we can get here with a codec that isn't lowercase. Do you have a test source that we can look at?
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Sure, here's my test page that combines a few things:
https://brionv.com/misc/hls-test/ogv.html
The Opus audio track: https://brionv.com/misc/hls-test/caminandes-llamigos.webm.audio.opus.mp4
The actual codec fourCC for Opus in MP4 is "Opus" (0x7375704F) -- it is not lowercased in the actual binary file.
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I'll pull up the local source and double-check versions of everything when I get a chance -- feel free to shoot any questions on my usage and I'll try my best to answer. :)
I'm not 100% confident I'm correctly labeling everything in the m3u8 for the Opus track version. (iOS accepts the MP3 audio version.)
Codecov Report
@@ Coverage Diff @@
## main #1219 +/- ##
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Coverage 85.40% 85.40%
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Files 40 40
Lines 9963 9963
Branches 2308 2308
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Hits 8509 8509
Misses 1454 1454
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The Opus box name is capitalized, but MediaSource expects a lowercase
"opus" codec string, which was causing unexpected failures in Chrome
and Firefox.
Now matches behavior of mux.js for audio tracks by forcing the box
type to lowercase before returning it as a codec string.
Description
HLS streams with Opus audio tracks in fragmented MP4 weren't working in Chrome and Firefox due to reading the codec string as "Opus" with a capital "O", which MediaSource rejects.
Specific Changes proposed
Forcing the box name string to lowercase resolves the specific problem with Opus; all other known codec strings are lowercase. mux.js appears to use the same logic when returning codec strings, so this is not expected to be problematic.
Requirements Checklist