[FFmpeg-trac] #5220(ffplay:new): ffplay lag with some resolutions when using i915 and SNA acceleration method

[FFmpeg]

#5220: ffplay lag with some resolutions when using i915 and SNA acceleration
method
-------------------------------------+-------------------------------------
             Reporter:  VittGam      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  ffplay       |                  Version:  git-
             Keywords:  i915, sna,   |  master
  uxa                                |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Hello,

 When using `SNA` acceleration on an Intel GMA915 video card (IBM !ThinkPad
 X41, screen is 1024x768), I'm having some problems with these resolutions
 in ffplay:

 - 1018x576 through 1037x576

 The problems are: increased IO-Wait and general lag of the mouse and
 screen, and frame drop in ffplay.

 Width values smaller than 1018 or bigger than 1037 work fine instead. Even
 1280x576 works perfectly.

 The same problem is reproduced with other height values, such as 480.

 A simple test case for this is:

 {{{
 ffplay -f lavfi -i testsrc=s=1024x576:r=25
 }}}

 - ffmpeg is latest (`7042a55`) from Git
 - Kernel is `4.4.1-2-ARCH`
 - Distro is Arch Linux
 - Desktop compositor is KWin from Plasma 5.

 When using the older `UXA` acceleration method instead of `SNA` in the X
 server, the problem goes completely away.

 Is this an ffplay issue? If not, should I report this problem to the i915
 developers, the KWin developers, or the SDL developers?

 Thank you,
 Vittorio G

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Ticket URL: <https://trac.ffmpeg.org/ticket/5220>
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