Alternate Surround Audio in HLS and MPD SMIL

Wowza Streaming Engine
1

Hi,

We have ABR streams with mutiple audio and video bitrates and would like to add extra audio channels with surround sound in AAC and AC-3 formats. We’ve successfully made the SMIL for MPD but for HLS it’s giving us nightmares. Here’s what the (simplified) SMIL looks like for MPD:

<?xml version="1.0" encoding="UTF-8"?>
<smil title="">
<body>
<switch>
<video height="360" width="640" src="mp4:MX586152-2223388-967603921890259.mp4">
<param name="videoBitrate" value="892928" valuetype="data"/>
<param name="audioBitrate" value="131072" valuetype="data"/>
<param name="audioRole" value="Stereo" valuetype="data"/>
</video>
<video height="480" width="852" src="mp4:MX586152-2223384-690093338489533.mp4">
<param name="videoBitrate" value="1763328" valuetype="data"/>
<param name="audioBitrate" value="131072" valuetype="data"/>
<param name="audioRole" value="Stereo" valuetype="data"/>
</video>
<video height="576" width="1024" src="mp4:MX586152-2222174-151339054107667.mp4">
<param name="videoBitrate" value="2363392" valuetype="data"/>
<param name="audioBitrate" value="196608" valuetype="data"/>
<param name="audioRole" value="Stereo" valuetype="data"/>
</video>
<video height="720" width="1280" src="mp4:MX586152-2227310-882769763469696.mp4">
<param name="videoBitrate" value="3131392" valuetype="data"/>
<param name="audioBitrate" value="196608" valuetype="data"/>
<param name="audioRole" value="Stereo" valuetype="data"/>
</video>
<video src="mp4:MX586152-2338134-072136878967286.aac">
<param name="audioBitrate" value="393216" valuetype="data"/>
<param name="audioOnly" value="TRUE" valuetype="data"/>
<param name="audioRole" value="AAC 5.1" valuetype="data"/>
</video>
<video src="mp4:MX586152-2338268-952219665050507.ac3">
<param name="audioBitrate" value="393216" valuetype="data"/>
<param name="audioOnly" value="TRUE" valuetype="data"/>
<param name="audioRole" value="AC-3 5.1" valuetype="data"/>
</video>
</switch>
</body>
</smil>

I’m not sure if we can misuse the audioRole this way but it works!\

How to change the SMIL so it also works for HLS. The https://www.wowza.com/docs/how-to-use-alternative-audio-or-video-tracks-with-apple-hls-streams page does not explain how to maintain the different audio and video bitrates, and just add the two alternate audio channels.

Anybody?

Thanks at lot.

2

Sorry you didn’t get an answer from the community, but this is a workflow that most folks may not have experience with. I know we’ve worked together with you in support tickets in the past, so I asked an engineer to take a peek at this post and they said it will require one. This a bit of a tricky configuration to nail down in the forums with wanting to create an HLS packetizer in parallel. It most likely requires a second SMIL file.

Let’s proceed through a ticket though so we can have full access to your files/logs and properly test and give you the correct guidance. Thanks Joost.