[FFmpeg-trac] #11165(undetermined:new): VP9 decoding problem

[FFmpeg]

#11165: VP9 decoding problem
-------------------------------------+-------------------------------------
             Reporter:  Mista_D      |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:  VP9 alpha    |               Blocked By:
  yuva420p overlay                   |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Description changed by Mista_D:

Old description:

> FFmpeg doesn't seem to recognize VP9 encoded alpha channel file
> (yuva420p). It decodes it by default with VP8 and therefore fails to see
> alpha channel in WEBM.
>
> This use case works well, overlay is good, alpha is crystal clear:
> `ffmpeg -i udp -c:v libvpx-vp9 -i ov3.webm -filter_complex
> [0:v][1:v]overlay -t 5 rtmp`
>
> Same file, same stream, but overlay doesn't work properly. Screen turns
> black with graphics on top:
> `ffmpeg -i udp -filter_complex
> "movie=ov3.webm:s=dv[ov];[0:v][ov]overlay,zmq" -t 5 rtmp`
>

> webm file was originally generated from ProRes MOV, which works well in
> both scenarios, but is too huge to be properly used for a long file.
> movie filter is mandatory for ZMQ to work.
>
> Thank you all for your work and awesome talents that you dedicate for
> this magnificent video engineering apparatus!

New description:

 FFmpeg doesn't seem to recognize VP9 encoded alpha channel file
 (yuva420p). It decodes it by default with VP8 and therefore fails to see
 alpha channel in WEBM.

 This use case works well (decoder is forced to vp9), overlay is good,
 alpha is crystal clear:
 `ffmpeg -i udp -c:v libvpx-vp9 -i ov3.webm -filter_complex
 [0:v][1:v]overlay -t 5 rtmp`

 Same file, same stream, but overlay doesn't work properly. Screen turns
 black with graphics on top:
 `ffmpeg -i udp -filter_complex
 "movie=ov3.webm:s=dv[ov];[0:v][ov]overlay,zmq" -t 5 rtmp`


 webm file was originally generated from ProRes MOV, which works well in
 both scenarios, but is too huge to be properly used for a long file. movie
 filter is mandatory for ZMQ to work.

 Thank you all for your work and awesome talents that you dedicate for this
 magnificent video engineering apparatus!

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Ticket URL: <https://trac.ffmpeg.org/ticket/11165#comment:1>
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