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bbfa235
(Get the code!)
Created attachment 47585
Screenshot showing strange artifact(s) in tearing.
I downloaded one of the youtube video's mr. Savin linked to and made a screenshot too.
This is a screenshot of "Tearing test for Flash video player (30p source).1080p.mp4" played back using 'mplayer -vo xv', with XFCE compositing enabled. The turning compositing off does not make a difference and gives identical results. Also '-vo gl' gives identical results.
There are two interesting things to note here. The first is that there is not just *one* line where the video tears, but many (really a lot tbh). This can be seen in the previous screenshot of the playground too, but here it becomes really apparent.
What is even more interesting is the the strange artefact which can be seen on the right-most line, just below the middle of the screen. Here we can see *on the same line part* of the new AND of the old line (the lines in the video are moving left-to-right)! So the small thin upstanding line to the right is actually part of the next frame, and hence we are seeing parts of two frames on the same line.
Combining the above two facts I don't think this is a simple 'scanline interrupt not being triggered' bug, but indeed something else. This would also explain why mr. Savin's patch doesn't seem to fix the issue. Unfortunately I have no idea what could cause such strange artefacts in the video rendering...