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Support IMSC1 in HLS #986

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avelad opened this issue Aug 24, 2017 · 4 comments
Closed

Support IMSC1 in HLS #986

avelad opened this issue Aug 24, 2017 · 4 comments
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@joeyparrish
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status: archived Archived and locked; will not be updated type: enhancement New feature or request
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v2.3.0

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@avelad
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avelad commented Aug 24, 2017 •
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IMSC1 in HLS

Carried as XML text inside fMP4 Segments
HLS defines support for the IMSC1 Text profile
Mark your Media Playlists as IMSC1 with the CODECS attribute
• CODECS="stpp.TTML.im1t, …"

//IMSC1 alongside WebVTT in a Master Playlist
#EXTM3U
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="vtt",LANGUAGE="eng",NAME="English",URI="vtt.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=90000,CODECS="avc1.4d001e,ac-3",SUBTITLES="vtt"
bipbop_gear1/prog_index.m3u8
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="imsc",LANGUAGE="eng",NAME="English",URI="imsc.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=90000,CODECS="avc1.4d001e,ac-3,stpp.TTML.im1t",SUBTITLES="imsc"
bipbop_gear1/prog_index.m3u8

Documentation:
https://devstreaming-cdn.apple.com/videos/wwdc/2017/504op4c3001w2f222/504/504_advances_in_http_live_streaming.pdf
https://developer.apple.com/videos/play/wwdc2017/504/
https://developer.apple.com/streaming/HLS-WWDC-2017-Preliminary-Spec.pdf
@joeyparrish joeyparrish added flag: good first issue This might be a relatively easy issue; good for new contributors type: enhancement New feature or request labels Aug 24, 2017
@joeyparrish
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We already support TTML in MP4 (independent of any particular manifest format such as HLS or DASH). The parser for TTML in MP4 is registered by MIME type and codec string, so we can simply add "stpp.TTML.im1t" to that registration:

https://github.com/google/shaka-player/blob/33c38e9c7ef47abb35b7bd27e374999ab5b64b22/lib/text/mp4_ttml_parser.js#L91

@joeyparrish joeyparrish added this to the v2.3.0 milestone Aug 24, 2017
@joeyparrish joeyparrish self-assigned this Aug 24, 2017
@ismena
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ismena commented Aug 24, 2017

Small nit: hls parser currently assumes all text streams it encounters are vtt, so will need to update it as well.

@joeyparrish joeyparrish removed the flag: good first issue This might be a relatively easy issue; good for new contributors label Aug 28, 2017
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This turns out to be much more complicated than I realized. Still working on the solution. Thanks!

joeyparrish added a commit that referenced this issue Aug 31, 2017
@joeyparrish
Add support for MP4+TTML in HLS
30d32b1 
Previously, our HLS implementation only supported WebVTT, because
that seemed to be the only supported format in HLS.

Now, we add support for other formats by extending the MIME and codec
guessing system to text streams.  We also add a parser registration
for HLS's new "stpp.TTML.im1t" codec string.

Closes #986

Change-Id: I0a58ca4650675ff0546e36edf4114290f7931239
@joeyparrish
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Cherry-picked to v2.2.1

@shaka-project shaka-project locked and limited conversation to collaborators Mar 22, 2018
@shaka-bot shaka-bot added the status: archived Archived and locked; will not be updated label Apr 15, 2021
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@ismena @joeyparrish @avelad @shaka-bot