[FFmpeg-trac] #9532(avcodec:new): Blocks with VDPAU and H264/1080i

FFmpeg trac at avcodec.org
Thu Nov 25 21:56:12 EET 2021

#9532: Blocks with VDPAU and H264/1080i
             Reporter:  Klaas de     |                     Type:  defect
  Waal                               |
               Status:  new          |                 Priority:  normal
            Component:  avcodec      |                  Version:  4.4.1
             Keywords:  blocks       |               Blocked By:
  vdpau h264 interlaced              |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Playing back H264 1080i recordings with MythTV frontend player gives
 blocking artifacts when VDPAU hardware decoding is used. Playback is OK
 when software decoding is used.

 The blocking artifacts appear often, but not always, for a short time when
 skipping backward and forward. Sometimes the blocking artifacts also
 appear on start of playback.
 Continuous playback is OK, it is the first second after the skip that
 gives the problems.

 The problem has been reproduced with the mpv player when VDPAU hardware
 decoding is configured; also here playback is OK when software decoding is

 The problem is bisected and it is caused by the following commit:

 commit 99042c2bf6cc79006036502a6abbec5e51f73673
 Author: James Almer <jamrial at gmail.com>
 Date:   Mon Mar 8 23:10:10 2021 -0300

     avcodec/h264_slice: don't copy frame data during error concealment

     In addition to the fact that av_image_copy() cannot handle hardware
 pixel formats,
     h->short_ref[0]->f may not be writable at this point.

     Based on a patch by Hendrik Leppkes.

     Signed-off-by: James Almer <jamrial at gmail.com>

 Reversing this patch in the release/4.4 tree does solve the problem for
 MythTV and for the mpv player.

 The mpv player command used:
 $ mpv -vo=vdpau --hwdec=vdpau tweevoortwaalf_ffmpeg.ts
Ticket URL: <https://trac.ffmpeg.org/ticket/9532>
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