[FFmpeg-trac] #7523(undetermined:new): VAAPI: Fail to Decode an H264 LP Multi-Slice Encoded Video

FFmpeg trac at avcodec.org
Tue Oct 30 06:05:02 EET 2018

#7523: VAAPI: Fail to Decode an H264 LP Multi-Slice Encoded Video
             Reporter:  uartie       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  vaapi        |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0

Comment (by uartie):

 This bug is not really about i965 backend driver.  It was only mentioned
 because it was unclear whether i965 should actually support it or if it
 was because of a HW limitation.  In case of HW limitation, the conclusion
 would be that iHD is reporting it wrong.  But, HW limitation or not, it
 seemed odd that i965 has logic to support VAConfigAttribEncMaxSlices > 1
 for LP but not support for VAConfigAttribEncSliceStructure.

 Nonetheless, on i965, VAConfigAttribEncSliceStructure returns NOT
 SUPPORTED, and ffmpeg doesn't get choked up about
 VAConfigAttribEncMaxSlices > 1... and thus, refuses to proceed with
 encoding.  This seems like reasonable behavior for ffmpeg in that case,

 Finally (the original reason for this bug), since iHD
 VAConfigAttribEncSliceStructure returns {{{EQUAL_ROWS | MAX_SLICE_SIZE}}},
 ffmpeg proceeds to encode it with this setting since iHD said it's
 supported.  Unfortunately, iHD seems to have trouble encoding with this

 So, I'm not sure what you would expect needs patched in ffmpeg.

Ticket URL: <https://trac.ffmpeg.org/ticket/7523#comment:5>
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