How to add support for multiple audios to VOD SMIL file?

Wowza Streaming Engine
1

Hi community! I created a channel with a VOD playlist from a SMIL file that broadcasts 24/7. How do I set up support for multiple audio tracks? It is necessary to be able to change the audio language.

2

Hi,
It sounds like you have live streams created from on-demand content and it’s the live streams which you’d like to have multiple audio tracks and allow switching at the player side.

To do this, you’ll need to publish the live stream (from VOD) multiple times (one for each audio track) and then in a different .smil (one for playback) reference all of the streams. The player will then use the .smil file for playback and allow switching between the streams to change the audio.

If this doesn’t answer your question or you need further support, I recommend that you create a support ticket to discuss this topic in more detail.

Regards,
Jason Hilton
Senior Technical Support Engineer
WOWZA | The solution you start with, the partner you scale with.

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1 Like
3

Thanks for the clarification!
One more question — can this also be achieved using the wse-plugin-multitrackvod.zip module? I’m currently running a 24/7 channel with a VOD playlist and would like to provide multiple audio tracks (languages) within the same stream, rather than publishing separate live streams for each track.

Would the wse-plugin-multitrackvod plugin be a suitable approach for this case?

4

Hi Arman,
The ModuleMultiTrackVOD module allows you to play a VOD asset which contains multiple tracks and select the track based on the appropriate index (audioindex, videoindex or dataindex).

So, if you wanted to switch the track from one language to another while the content plays, you could create a .smil file for playback which then references the streams with the appropriate audio tracks (index) you want using the query string after the file name.

Please see an example below showing a .smil which will allow the selection of 3 different audio tracks.

<?xml version="1.0" encoding="UTF-8"?>
<smil title="">
	<body>
		<switch>
			<video src="mp4:MultiAudioVOD.mp4?audioindex=0" systemLanguage="eng" title="Eng">
				<param name="videoBitrate" value="3438000" valuetype="data"></param>
				<param name="audioBitrate" value="127000" valuetype="data"></param>
			</video>
			<video src="mp4:MultiAudioVOD.mp4?audioindex=1" systemLanguage="fre" title="Fre">
				<param name="videoBitrate" value="3438000" valuetype="data"></param>
				<param name="audioBitrate" value="128000" valuetype="data"></param>
			</video>
			<video src="mp4:MultiAudioVOD.mp4?audioindex=2" systemLanguage="ger" title="Ger">
				<param name="videoBitrate" value="3438000" valuetype="data"></param>
				<param name="audioBitrate" value="129000" valuetype="data"></param>
			</video>
		</switch>
	</body>
</smil>

You may notice I’ve changed the audio bitrate for each rendition to help with the selection of the audio track on the playback side when trying to switch stream.

Similar to how this is configured in a playback .smil file, you may be able to define the audio index in the .smil file used for creating the live playlist from your VOD assets.

However, if this is your use case, you’d need to test this to ensure it works.

Regards,
Jason Hilton
Senior Technical Support Engineer
WOWZA | The solution you start with, the partner you scale with.

Manage your Support cases online
Bookmark our FAQ page
Bookmark our Status page