I tried doing the same previously, and the only way I could get M3U8 to work was via HTTP. I couldn't figure out any way to get it to work from tmp:. Having said that, I don't think I ever tried it with a "file://" protocol prefix. I doubt it would make a difference, but it might. The other possibility would be to set up a simple web server in-channel that could serve the playlist via HTTP.
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