[Webkit-unassigned] [Bug 191257] [GStreamer][MSE] pixelated video when MSE is enabled

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=191257

--- Comment #6 from Alicia Boya García <aboya at igalia.com> ---
I was going to send you a list, but while I was trying it, I found the element causing pixelation bug. It's the VP9 decoder from libav.

Using the decoder from libav (avdec_*), it pixelates:

$ gst-launch-1.0 pushfilesrc location=<(cat /tmp/SourceBuffer-2-video-0.webm) ! matroskademux ! avdec_vp9 ! autovideosink

Using vp9 elements from GStreamer, it works without issues:

$ gst-launch-1.0 pushfilesrc location=<(cat /tmp/SourceBuffer-2-video-0.webm) ! matroskademux ! vp9dec ! autovideosink

vp9dec has a higher rank than avdec_vp9, but you probably built gst-plugins-good without libvpx so it had to go with avdec_vp9 anyway. Reconfiguring gst-plugins-good with libvpx and rebuilding should fix the issue.

It's probably worth it to report this as a bug in avdec_vp9 anyway (which may easily end up being a bug in libav).

That does not explain why this did not happen on regular WebM playback, but it may be something different about the way YT files are encoded that the other WebM test files you tried may do differently... Indeed, just checking it now, the test file from https://www.webmfiles.org/demo-files/ is actually encoded in VP8, not VP9, so it's a completely different video format even if the container format is also WebM.

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