[Bug 28114] Full screen video playback choppy after git commit 78e7047c

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue May 18 09:57:36 PDT 2010


--- Comment #14 from Pauli <suokkos at gmail.com> 2010-05-18 09:57:36 PDT ---
> --- Comment #10 from Michel Dänzer <michel at daenzer.net> 2010-05-18 08:34:04 PDT ---
> (In reply to comment #9)
>> I realy don't know what is real problem because the Attila's patch
>> that fixes the problem is practicaly moving the XV buffer to VRAM that
>> should be very slow for everyone.
> Actually it seems rather unusually slow on your system. Even this PowerBook
> (which doesn't even have write combining) manages more than 100 MB/s for CPU
> writes to VRAM.

Yes. My hw is the lowest that I have seen but I have seen results that
writes to vram even in some r600/r700 cards are slower than 20MB/s.

>> I can later today upload a test application to see how fast memory access is to
>> VRAM. But I still don't understand why GPU reading from GTT is very slow for
>> X1300 (laptop card?).
> I'm not sure either, but I guess the bicubic filtering could require quite a
> lot of bandwidth for texture sampling.

I guess it might be that bicubic filtering may need to read same
memory area multiple times causing extra bandwidth use. So with
bicubic fragment shader (or similar) actual video should be first
uploaded to VRAM before doing the bicubic scaling.

> --- Comment #11 from AttilaN <attila123456 at gmail.com> 2010-05-18 09:29:45 PDT ---
> Any idea why only some videos are affected? 720p HD plays fine, as well as
> other, smaller ones with various aspect ratios/codecs. does the linked test
> video play smoothly on your computer?

Yes. It plays smoothly in fullscreen (1024x768). But bicubic filtering
is not implemented for my hw.

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