[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 #4 from Alicia Boya García <aboya at igalia.com> ---
Created attachment 353968

  --> https://bugs.webkit.org/attachment.cgi?id=353968&action=review

[MSE][Debug] Add debug option to dump appends

I'm attaching a debug patch that can be used to dump the MSE appends. Please build WebKit with it and then run with WEBKIT_MSE_DUMP_APPENDS=1 set as an environment variable and play one of the offending videos without seeking.

You should get a file like /tmp/SourceBuffer-2-video-0.webm. This file contains the MSE video byte to byte as YouTube pushes it to WebKit.

Then play it like this (I'm assuming a Bash shell). This replicates all the stages of playback with the same elements WebKit uses.

$ gst-launch-1.0 pushfilesrc location=<(cat /tmp/SourceBuffer-2-video-0.webm) ! matroskademux ! decodebin ! glupload ! glcolorconvert ! glimagesink

If you are running WebKit inside jhbuild (which is the default if you are using `run-minibrowser`), you should run it in jhbuild as well, e.g. by prepending `jhbuild-wrapper --gtk run` to the previous command, i.e:

$ jhbuild-wrapper --gtk run gst-launch-1.0 pushfilesrc location=<(cat /tmp/SourceBuffer-2-video-0.webm) ! matroskademux ! decodebin ! glupload ! glcolorconvert ! glimagesink

(The point is to make sure you are using the same GStreamer instance in both cases.)

I would expect this command to reproduce the issue. Then we could switch elements until finding which one is causing the problem in your system.

If the above command does not reproduce the issue then it's difficult that I am able to debug the issue without having a system where it is reproducible.

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