[FFmpeg-trac] #7564(avfilter:new): hwdownload fails when size changes

[FFmpeg]

#7564: hwdownload fails when size changes
-------------------------------------+-------------------------------------
             Reporter:  msiders      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avfilter     |                  Version:  git-
             Keywords:  hwdownload,  |  master
  resize                             |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 When some filter changes the size of the frames, then the "hwdownload"
 filter doesn't produce the correct output.

 How to reproduce, Test 1 working:
 {{{
 % ffmpeg -stream_loop -1 -y \
  -loglevel error \
  -hwaccel cuvid \
  -c:v h264_cuvid \
    -i "../Day Flight.mpg" \
  -filter_complex
 "hwdownload,format=nv12,scale=400:300,hwupload,scale_cuda=800:600,hwdownload,format=nv12,fps=25,scale=800:600"
 \
  -c:v h264 \
  -f mpegts out.ts
 }}}

 When running this play, pause the execution with key <c> and type
 {{{
 Parsed_scale_2 -1 w 200
 }}}

 This changes the behaviour of the first software scale filter to a width
 of 200.
 And the result is correct.

 How to reproduce, Test 2 with errors:
 {{{
 % ffmpeg -stream_loop -1 -y \
  -loglevel error \
  -hwaccel cuvid \
  -c:v h264_cuvid \
    -i "../Day Flight.mpg" \
  -filter_complex
 "hwdownload,format=nv12,scale=400:300,hwupload,hwdownload,format=nv12,fps=25,scale=800:600"
 \
  -c:v h264 \
  -f mpegts out.ts
 }}}

 Then repeat the change of the software scaling filter with "Parsed_scale_2
 -1 w 200".
 Now the output has a vertical green line above pixels 200, and the image
 only occupies the left side. The right side is occupied by ancient still
 image.

 So, the problem is: the "hwupload" filter does the correct behaviour.
 However, the "hwdownload" filter doesn't.

 Please, fix this bug!

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7564>
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