Dynamic Packaging - Audio only : HLS support multiple bitrate with same language/codec ?

Question

Dynamic Packaging - Audio only : HLS support multiple bitrate with same language/codec ?

XAVIER LAFFARGUE 51

Hi,

I would like to know if Azure Dynamic Packaging support multiple bitrates on HLS with the same language/codec (only the bitrate/quality change).

I ask because after severals tests I only see one bitrate in the manifest HLS, but Dash & Smooth displays all bitrates

Smil :

<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
<head>
<meta name="formats" content="mp4" />
</head>
<body>
<switch>
<audio src="audio64.mp4" systemBitrate="64000" systemLanguage="fr" />
<audio src="audio128.mp4" systemBitrate="128000" systemLanguage="fr" />
</switch>
</body>
</smil>

2 answers

Your answer

Answer 1

Hi Xavier,

Is the input for this stream going to be VOD (on-demand) or is this a live feed coming in via our pass-through Live event type?

Also, it would be good to start from your expectation in the HLS or DASH manifest. Are you trying to create multiple renditions of the same asset, with the ability to select different bitrates, or is your goal to try to do some form of Adaptive audio switching from 128kbps down to 64kbps?
Because those two would be shown slightly differently in the manifests. Also, one thing to keep in mind is that not many players out there support adaptive audio switching. They just are not tuned to do it very well.

Answer 2

XAVIER LAFFARGUE 51

Hi @John Deutscher

Is the input for this stream going to be VOD (on-demand) or is this a live feed coming in via our pass-through Live event type?

VOD

I would like to have something like this :

#EXT-X-STREAM-INF:BANDWIDTH=64000,CODECS="mp4a.40.2"  
QualityLevels(64000)/Manifest(audio_fr,format=m3u8-cmaf)  
#EXT-X-STREAM-INF:BANDWIDTH=128000,CODECS="mp4a.40.2"  
QualityLevels(128000)/Manifest(audio_fr,format=m3u8-cmaf)

Actually I've :

#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio",NAME="audio_fr",LANGUAGE="fr",DEFAULT=YES,AUTOSELECT=YES,URI="QualityLevels(64000)/Manifest(audio_fr,format=m3u8-aapl)"  
#EXT-X-STREAM-INF:BANDWIDTH=64000,CODECS="mp4a.40.2",AUDIO="audio"  
QualityLevels(64000)/Manifest(audio_fr,format=m3u8-cmaf)

John Deutscher 241 Reputation points

2021-12-06T19:18:10.517+00:00

Do you want them to be in the same Audio rendition group "audio_fr" or do you want them to be in separate audio rendition groups with different names?
I believe the naming of the "audio_fr" group may be the issue here. I can check to see if that is supported or not depending on your scenario.
XAVIER LAFFARGUE 51 Reputation points

2021-12-06T19:23:43.613+00:00

In the same audio rendition groupe "audio_fr" :)
John Deutscher 241 Reputation points

2021-12-06T19:26:50.607+00:00

Thanks! Checking.... standby
XAVIER LAFFARGUE 51 Reputation points

2021-12-07T19:56:48.25+00:00

Do you have some news :) ?
John Deutscher 241 Reputation points

2021-12-07T20:02:50.5+00:00

Sorry for delay - right people are out of office, so waiting on response. Will update when I can.
Ning Lin 1 Reputation point Microsoft Employee

2021-12-09T23:43:02.17+00:00

Our dynamic packager is only able to support multiple audio tracks (EXT-X-MEDIA) and not multiple audio bitrates (EXT-X-STREAM-INF) like you were hoping for. I have not found documentation that the native HLS player could support an automatic switch between different audio bitrates. Do you have have an example of such a stream (either documented or working sample)?
XAVIER LAFFARGUE 51 Reputation points

2021-12-10T00:14:06.483+00:00

Sure, for example : https://rcavmedias-vh.akamaihd.net/i/7e3b848f-bf4f-43e0-91f1-134829f499d2/2021-12-09_05_30_00_matinsdici_0000_,64,128,.mp4.csmil/master.m3u8

(Apple native player works well)
John Deutscher 241 Reputation points

2021-12-10T00:30:50.757+00:00

The Akamai link works on my iPhone, but I can't force or test the adapting - so not sure if it is really adapting or not...

What is the use case for adaptive audio in your situation Xavier? Are there networks where 128Kbps really is unavailable, and it has to drop to 64kbps these days?
Are you trying to reach an audience that has less than 128kbps available for download?
XAVIER LAFFARGUE 51 Reputation points

2021-12-10T00:48:35.17+00:00

Try on Safari on MacOS, you will see the adaptation or you can try on this test player: https://hls-js.netlify.app/demo/

We want to provide the best mobile experience (our players lower the quality automatically in certain circumstances), and we plan to add a new bitrate in the future. All our apps support it
John Deutscher 241 Reputation points

2021-12-13T19:39:03.097+00:00

@XAVIER LAFFARGUE - I'm looking around for some good examples that show adaptive bitrate audio in renditions groups with Video in HLS.

The sample you send is just two layers of audio, but I would like to collect more samples that are complex with Video as well.

I see that Apple provides several advanced stream samples with renditions - but they never show adaptive audio. They only show selectable audio for different codecs like AAC-LC, Dolby Digital, Atmos, etc. for multi-channel scenarios.

https://developer.apple.com/streaming/examples/

Do you know of any samples that show how to setup adaptive audio in a Group along with video in a CMAF rendition? I may need to ask around more in the industry to get some examples of this.

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Dynamic Packaging - Audio only : HLS support multiple bitrate with same language/codec ?

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