[FFmpeg-user] QT ProRes 4444 w/ Alpha

[Ashkan Daie]

I have 2 different issues both with QT ProRes 4444 w/ alpha as my input:


   1. When trying to convert to qtrle, I do not get the alpha channel. If I
   first convert to png and then use the png output as the source for qtrle I
   do get alpha channel. Is there a way to convert from prores 4444 directly
   to qtrle w/o losing alpha?
   - *Command to convert from prores to qtrle (Does not decode alpha
      channel) - *ffmpeg -i qt_4444_alpha.mov -vcodec qtrle rle.mov
      - *Command to convert from prores to png* - ffmpeg -i
      qt_4444_alpha.mov -vcodec png .\png2\test_%04d.png
      - *Command to convert from png to qtrle* - ffmpeg -i
      ./png2/test_%04d.png -vcodec qtrle test.mov
   2. When converting from QT ProRes 4444 w/ alpha to h264 I completely
   lose alpha channel. I know that h264 does not support alpha. I used Adobe
   Media Encoder w/ same source to h264 and it looks like it blends the alpha
   channel in the final output. Anyway I can get the same results using ffmpeg?

Thank you,
Ashkan