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Hi,
I signal a descriptive audio tracks (https://learn.microsoft.com/en-us/azure/media-services/latest/signal-descriptive-audio-howto?tabs=net)
So I use this in my ism file :
<?xml version="1.0" encoding="utf-8"?>
<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
<head>
<meta name="formats" content="mp4" />
</head>
<body>
<switch>
<video src="filename_256.mp4" systemBitrate="256097" />
<video src="filename_400.mp4" systemBitrate="400137" />
<video src="filename_500.mp4" systemBitrate="500121" />
<video src="filename_800.mp4" systemBitrate="800242" />
<video src="filename_1200.mp4" systemBitrate="1200379" />
<video src="filename_2000.mp4" systemBitrate="1999913" />
<audio src="filename_1200.mp4" systemBitrate="128000" systemLanguage="fre">
<param name="trackName" value="audio1_fr" valuetype="data" />
</audio>
<audio src="filename_dv.mp4" systemBitrate="128000" systemLanguage="fre">
<param name="role" value="alternate" valuetype="data" />
<param name="accessibility" value="description" valuetype="data" />
<param name="trackName" value="audio0_frdv" valuetype="data" />
</audio>
</switch>
</body>
</smil>
The hls manifest generated is :
#EXTM3U
#EXT-X-VERSION:7
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio",NAME="audio1_fr",LANGUAGE="fre",CHANNELS="2",URI="QualityLevels(128000)/Manifest(audio1_fr,format=m3u8-cmaf)"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio",NAME="audio0_frdv",LANGUAGE="fre",DEFAULT=YES,AUTOSELECT=YES,CHARACTERISTICS="public.accessibility.describes-video",CHANNELS="2",URI="QualityLevels(128000)/Manifest(audio0_frdv,format=m3u8-cmaf)"
#EXT-X-STREAM-INF:BANDWIDTH=408867,RESOLUTION=384x216,CODECS="avc1.42c01e,mp4a.40.2",AUDIO="audio"
QualityLevels(256097)/Manifest(video,format=m3u8-cmaf)
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=408867,RESOLUTION=384x216,CODECS="avc1.42c01e",URI="QualityLevels(256097)/Manifest(video,format=m3u8-cmaf,type=keyframes)"
#EXT-X-STREAM-INF:BANDWIDTH=556076,RESOLUTION=480x270,CODECS="avc1.42c01e,mp4a.40.2",AUDIO="audio"
QualityLevels(400137)/Manifest(video,format=m3u8-cmaf)
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=556076,RESOLUTION=480x270,CODECS="avc1.42c01e",URI="QualityLevels(400137)/Manifest(video,format=m3u8-cmaf,type=keyframes)"
#EXT-X-STREAM-INF:BANDWIDTH=658259,RESOLUTION=512x288,CODECS="avc1.42c01e,mp4a.40.2",AUDIO="audio"
QualityLevels(500121)/Manifest(video,format=m3u8-cmaf)
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=658259,RESOLUTION=512x288,CODECS="avc1.42c01e",URI="QualityLevels(500121)/Manifest(video,format=m3u8-cmaf,type=keyframes)"
#EXT-X-STREAM-INF:BANDWIDTH=964983,RESOLUTION=640x360,CODECS="avc1.42c01e,mp4a.40.2",AUDIO="audio"
QualityLevels(800242)/Manifest(video,format=m3u8-cmaf)
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=964983,RESOLUTION=640x360,CODECS="avc1.42c01e",URI="QualityLevels(800242)/Manifest(video,format=m3u8-cmaf,type=keyframes)"
#EXT-X-STREAM-INF:BANDWIDTH=1373923,RESOLUTION=852x480,CODECS="avc1.4d401f,mp4a.40.2",AUDIO="audio"
QualityLevels(1200379)/Manifest(video,format=m3u8-cmaf)
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=1373923,RESOLUTION=852x480,CODECS="avc1.4d401f",URI="QualityLevels(1200379)/Manifest(video,format=m3u8-cmaf,type=keyframes)"
#EXT-X-STREAM-INF:BANDWIDTH=2191047,RESOLUTION=852x480,CODECS="avc1.4d401f,mp4a.40.2",AUDIO="audio"
QualityLevels(1999913)/Manifest(video,format=m3u8-cmaf)
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=2191047,RESOLUTION=852x480,CODECS="avc1.4d401f",URI="QualityLevels(1999913)/Manifest(video,format=m3u8-cmaf,type=keyframes)"
#EXT-X-STREAM-INF:BANDWIDTH=138976,CODECS="mp4a.40.2",AUDIO="audio"
QualityLevels(128000)/Manifest(audio0_frdv,format=m3u8-cmaf)
Bug : The first audio track should have "DEFAULT" attribute with YES value !! Actually, the default attribute is only on the second audio track.
And I can't reverse audio track because iOS/MacOS hls native player play the first audio track if this one not contain "DEFAULT=NO"
Note HLS specification :
"9.17. Within a group of Renditions (EXT-X-MEDIA tags having the same TYPE and GROUP-ID), those tags having the same LANGUAGE value should be ordered from most general to most specific. (Because CHARACTERISTICS are open-ended, the matching algorithm needs the ordering since it can’t interpret all the semantics.)"
Please fix this issue or found a workarround :) thanks!
Thanks for reporting the issue. I'll have the team take a look and see if we can find a workaround for you.
As a workaround, try to swap order of <audio/> entry in ism.
For the Default issue, we are aware of this bug and are actually working on adding an API for controlling the late binding of audio tracks to Assets from 3rd party or external encoder sources. That new API is planned for our next 6-month semester. We can update this Q&A when it is ready for use in the SDKs.
Thanks for you feedback @John Deutscher (MSFT) but your workaround doesn't work with the hls native player on iOS, this player play the alternate audio when I swap order.
Just to confirm, can you create a new locator for it? There might be a manifest cache somewhere.
I use a new asset
Hi @XAVIER LAFFARGUE I followed up with the product team since. Apologies the workaround didn't resolve the issue. The team is aware of the issue and a fix will be applied in a future API update.
Thanks @Ryan Hill
I need to wait the new API for controling the late binding audio or the fix will be applied before 6 month ?
The tentative timeframe is between late spring and late summer.