[FFmpeg-trac] #8724(avfilter:new): chromakey does not observe existing transparency

FFmpeg trac at avcodec.org
Wed Jun 10 14:56:46 EEST 2020

#8724: chromakey does not observe existing transparency
             Reporter:  zerodefect   |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avfilter     |                  Version:  git-
             Keywords:  chromakey,   |  master
  alpha                              |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Summary of the bug:

 The chromakey filter does not observe the existing alpha transparency in
 the source AVFrame when generating the output.

 How to reproduce:
 % ffmpeg -i video.mxf -i green_screen4.png -filter_complex
 -map "[out]" output.mp4

 ffmpeg version git-2020-06-08-d29aaf1 (Windows nightly automated build)

 I have created a test image (attached):
 * There is a transparent circle in each of the 4 corners of the image
 * There is a semi-transparent pink circle in the middle of the image.

 Compare the input image to the output image and note the differences.

Ticket URL: <https://trac.ffmpeg.org/ticket/8724>
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