#ProRes 4444 alpha dropped after renderMedia() (yuva → yuv)

2 messages · Page 1 of 1 (latest)

upper patrol
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ffprobe result :

ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,pix_fmt -of default=noprint_wrappers=1 output.mov

codec_name=prores
pix_fmt=yuv444p10le
upper patrol
#

I think this issue might be caused by how the ProRes profile is handled during the stitching step.

Even though I set proresProfile to 4444, the FFmpeg command generated during stitching uses -profile:v 3, which corresponds to ProRes 4444 (without alpha). This seems like it could explain why the output ends up as yuv444p10le instead of preserving alpha.

Here is the actual FFmpeg command used during stitching:

My assumption is that because profile:v is set to 3 during stitching, the alpha channel is dropped, even though pix_fmt is yuva444p10le and the PNG frames contain alpha.

It seems to be operating differently from the mapping method intended by remotion.
This feels like it might be a Remotion bug rather than expected behavior.
What do you think?