Overlay a VP9 video with an alpha channel using alpha blending

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The VP9 codec supports videos with an alpha channel, but simply overlaying them does not perform alpha blending. To achieve the desired result, specify libvpx-vp9 as the video codec just before the argument for the VP9 video to be overlaid.

-i background-video.mp4 specifies the video file to be used as the background.

-c:v libvpx-vp9 specifies libvpx-vp9 as the codec for the overlay video file that follows. Without this specification, the overlay will be applied, but the alpha channel will not be handled correctly.

-i overlay-vp9-video-with-alpha-channel.webm specifies the VP9-encoded video file with an alpha channel to be used as the overlay.

-filter_complex “[0:v][1:v]overlay” overlays the video specified by the second -i argument onto the video specified by the first -i argument.

  • by rna
  • Updated on: January 16, 2025
  • tags: #overlay 
ffmpeg -i background-video.mp4 -c:v libvpx-vp9 -i overlay-vp9-video-with-alpha-channel.webm -filter_complex "[0:v][1:v]overlay" out.mp4