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I have a set of 300 transparent png files and I would like to create a transparent video file from them. I'm using the ffmpeg command as follows:

ffmpeg -f image2 -i anim.%04d.png -r 30 -vcodec png video.webm

I know webm has an alpha channel according to this answer. The command creates the video but the transparency is completely lost. What am I doing wrong? Is it possible to create a transparent .mp4 with ffmpeg?

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You have to specify the pixel format, to force it to include the alpha channel, using the -pix_fmt option. You don't need to use png as your video codec either.

ffmpeg -i anim.%04d.png -r 30  -pix_fmt yuva420p video.webm
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  • What's the complex filter equivalent to -pix_fmt? Would format=yuva420p be enough? Feb 3, 2022 at 23:03
  • Not sure, that might be a good candidate for a new question
    – stib
    Feb 4, 2022 at 2:18
  • Is it possible to use this for a .mov video file?
    – aaragon
    Nov 2, 2022 at 18:11
  • -pix_fmt yuva420p not work in hevc and nvenc.
    – rint
    Sep 15, 2023 at 10:37
  • alpha isn't supported by hevc and nvenc
    – stib
    Oct 2, 2023 at 2:44

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