Audio codec preference on DASH/HLS

[Alvaro Velad]

Hello,

Are there any mechanism for prefer one codec over other?

I prefer reproduce ac-3 over acc, how can I do it?

Other example, ec-3 over ac-3 and acc. Example: https://tungsten.aaplimg.com/VOD/bipbop_adv_example_hevc/master.m3u8 (from https://developer.apple.com/streaming/examples/)

Thanks!

[Joey Parrish]

Hi Alvaro,

Currently, when multiple codecs are presented in the manifest and are supported by the browser, Shaka Player chooses the "most efficient" codec by bitrate.  This makes good sense for video, I think, but may make less sense for audio, where multi-channel streams may be preferable on platforms with multi-channel output capabilities, in spite of their increased bitrate.

If there is a better heuristic to choose codecs in a browser environment, (for example, by audio output channels), please let us know!

-Joey

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[Alvaro Velad]

Hi Joey,

I'm accord with you, chooses the "most efficient" codec by bitrate is good for video, but for audio, I'd prefer another heuristic.

I propose the following:

1. Add a preferredAudioNumChannelLanguage into configuration
   
2. Improve selectAudioLanguage function to allow language, role and numChannels
   
3. Change the current heuristic for audio codec selection.
   
• Choose the codec that has a track with the number of channels closest to the preference (preferredAudioNumChannelLanguage).
  
• If there are several that meet this requirement, choose the one with the lowest bandwidth.
• If there are not preferredAudioNumChannelLanguage configuration, follow the current logic of "most efficient" codec by bitrate

Example with the previous stream:

Audio tracks:

• AAC-LC - stereo @ 160 kbps
  
• AC-3 - 5.1 @ 384 kbps
  
• EC-3 - 5.1 @ 192 kbps
  

In Safari Browser or Edge Browser (both support all previous codecs):

case 1) preferredAudioNumChannelLanguage = 2, the player should choose AAC-LC - stereo @ 160 kbps

case 2) preferredAudioNumChannelLanguage = 6, the player should choose EC-3 - 5.1 @ 192 kbps

Joey, this make sense for you?

Alvaro

El martes, 29 de agosto de 2017, 20:42:52 (UTC+2), Joey Parrish escribió:

Hi Alvaro,

Currently, when multiple codecs are presented in the manifest and are supported by the browser, Shaka Player chooses the "most efficient" codec by bitrate.  This makes good sense for video, I think, but may make less sense for audio, where multi-channel streams may be preferable on platforms with multi-channel output capabilities, in spite of their increased bitrate.

If there is a better heuristic to choose codecs in a browser environment, (for example, by audio output channels), please let us know!

-Joey

On Mon, Aug 28, 2017 at 2:40 AM, Alvaro Velad <alvaro...@mirada.tv> wrote:

Hello,

Are there any mechanism for prefer one codec over other?

I prefer reproduce ac-3 over acc, how can I do it?

Other example, ec-3 over ac-3 and acc. Example: https://tungsten.aaplimg.com/VOD/bipbop_adv_example_hevc/master.m3u8 (from https://developer.apple.com/streaming/examples/)

Thanks!

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[Joey Parrish]

Sorry I missed this.  I'm catching up now, and I see this has been filed on github as https://github.com/google/shaka-player/issues/1013

We'll continue there.  Thanks!

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