Comment # 7 on bug 1219070 from Avu Zel

@Jan Engelhardt

avc1.64002a (299) / mp4a.40.2 (140) works (Live stream) even in youtube. This
could be pointing to opus processing library (or handling).

Mplayer plays the file just fine, gstreamer based totem too. I checked, audio
is opus-encoded. Surprisingly video codec is called VP9 though no transcoding
has happened.

Hope that helps.

ok, investigated a bit further: avc1 is only shown as soon as the black "error"
screen appears. During the time, when the preview picture is shown with the
start button, VP9 is shown as codec. As soon as it changes to black error
screen, it switches to avc1. This could mean the original stream is VP9/opus
encoded and would explain why the file contains VP9 streams.