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Adaptive Bitrate SMIL file syntax


We’re using an SMIL file to deliver ABR streaming to both an MPEG-DASH and HLS stream to jwplayer.

sources: [
{file: "https://wowza_server/_definst_/smil:sample.smil/manifest.mpd"},
{file: "https://wowza_server/_definst_/smil:sample.smil/playlist.m3u8"}]

As part of the SMIL we’re including the captions

    <video src="sample-high.mp4"    system-bitrate="3000000"/>
    <video src="sample-medium.mp4"  system-bitrate="1500000"/>
    <video src="sample-low.mp4"      system-bitrate="500000"/>
    <textstream src="" systemLanguage="eng" >
      <param name="isWowzaCaptionStream" value="true" />

The video works with both streams, but the captions only work properly with the MPEG-DASH stream. In the HLS stream, the captions are set to the lower left corner (instead of centered) and the CC selector shows “Off” or “Unknown CC” instead of “English”

I found this page on Wowza’s website: Understanding SMIL file syntax | Wowza Docs & APIs

But there wasn’t any reference for textstream options/parameters.

Are there any resources available that talk about textstream or how we can configure the SMIL to support some additional options for captions in the HLS stream?

Things we’ve tried:

We’ve tried using parameters such as “label”, “Title”, “srcLang” with values set to both “eng” or “English” but none of that has worked.

We’ve also tried those options in the textstream directly and also set as a param

Thank you for any assistance, or points in the right direction!


We do have a docs article that covers the textstream parameter in a smil file with some examples. I hope this helps.