ffmpegwebmblackmagic-fusion

FFMPEG DNxHR with Alpha to Webm

I'm trying to convert a video file exported from Blackmagic Fusion as DNxHR with Alpha checked to WebM or PNG. FFMPEG seems to ignore the alpha and the background is black. Is there something I need to do? This is what I'm currently using:

ffmpeg -ss 0.5 -i DNxHR444A.mov -vframes 1 test.png

or

ffmpeg -i DNxHR444A.mov -c:v libvpx-vp9 -crf 30 -b:v 0 test.webm

I can upload my test video if that helps. But it's quite large.

Solution

  • FFmpeg's DNXHD/R decoder does not support alpha. Either use another codec on export, or export alpha separately (it will be a grayscale picture). With the 2nd method, ffmpeg can combine the main image and the alpha for onward processing.