[FFmpeg-trac] #7399(undetermined:new): [ffmpeg-qsv][h264_ffmpeg]decode drop frames on iHD driver.

[FFmpeg]

#7399: [ffmpeg-qsv][h264_ffmpeg]decode drop frames  on iHD driver.
-------------------------------------+-------------------------------------
             Reporter:               |                    Owner:
  zhuqingliang                       |                   Status:  new
                 Type:  defect       |                Component:
             Priority:  normal       |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:  qsv          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by fulinjie):

 The frame dropping issue was caused by the reinitialization of the input
 stream.（In this stream，first 50 frames: 352x288,last 50 frames: 240x 196
 ）The reinitialization drops all the buffered pkts in libmfx.

 Provided a patch to cache the first frame causing the reinit and decode
 zero-size pkt to flush the buffered pkt before reinit. After all
 thebuffered pkts being flushed, resume to reinit and decode.

 commit id: 505679cb6d2cd0e7c1714e28e05a6b9cdc917991
 https://patchwork.ffmpeg.org/patch/10515/
 http://ffmpeg.org/pipermail/ffmpeg-devel/2018-September/234703.html

 Tested and got the same result with vaapi and ffmpeg ref:
 {{{
 $ ffmpeg -y -loglevel debug -hwaccel qsv -c:v h264_qsv -i reinit-
 large_420_8-to-small_420_8.h264 -vf
 'hwdownload,format=nv12,format=yuv420p' out_mfx.yuv
 ...
 $ md5sum out_mfx.yuv
 151bf4fac480ad53d8f62ed6cd43b55c  out_mfx.yuv
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/7399#comment:3>
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