[FFmpeg-trac] #4127(avcodec:new): h264 DXVA2 decoding regression on Intel GPUs

FFmpeg trac at avcodec.org
Fri Nov 21 20:27:33 CET 2014


#4127: h264 DXVA2 decoding regression on Intel GPUs
-------------------------------------+-------------------------------------
             Reporter:  johsmi       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  h264         |               Blocked By:
  regression                         |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by johsmi):

 Replying to [comment:1 heleppkes]:
 > Its more likely that before this change it would just skip those frames
 entirely, while now it tries to decode them (and fails). This isn't
 technically a regression.

 The difference is not just from skipping a few initial frames before the
 change. I've extracted all frames using this command line:
 {{{
 ffmpeg -hwaccel dxva2 -threads 1 -i green_start.mkv frames-%3d.ppm
 }}}
 206 frames are generated both before and after applying that change. I
 have also confirmed that the frames are identical after the initial bad
 frames (fc /B confirms no differences for a particular frame nr starting
 from frame 16).

 I've compared data before and after that change in some detail and one
 thing that does happen is that after the change, the first frame to decode
 has:
 {{{ctx_pic->pp.CurrPic=4 and ctx_pic->pp.RefFrameList = 03 02 01 00
 FF...}}}

 This ends up in the DXVA2 picture decoding parameter buffer and the call
 to IDirectXVideoDecoder_Execute fails.

 Before the change, the first frame has:
 {{{ctx_pic->pp.CurrPic=0 and ctx_pic->pp.RefFrameList = FF FF FF FF
 FF...}}}

 That call to IDirectXVideoDecoder_Execute succeeds.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/4127#comment:3>
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