FFMPEG: is there a way to re-encode changing only the colormatrix?

[marcorocchini]

IH cats

I wonder can I re-encode a MP4 changing the colormatrix fron 601 to 709 in vcodec copy? No? however is there a way to tell to ffmpeg that, in case of transcoding, that it have to change only the colormatrix and preserve all the video part as is?

thanks

[sneaker]

1. You can change the colormatrix flag but not content using a special ffmpeg build without re-encoding. But it is a bit buggy and not developed anymore.
https://forum.doom9.org/showthread.php?t=152419

2.
ffmpeg -i "input" -vf scale=in_color_matrix=bt601:out_color_matrix=bt709 -colorspace bt709 -c:v libx264 -crf 18 -preset medium -c:a copy "output.mp4"

See:
https://ffmpeg.org/ffmpeg-filters.html#scale
https://ffmpeg.org/ffmpeg-filters.html#colormatrix
https://trac.ffmpeg.org/wiki/colorspace
http://video.stackexchange.com/questions/16840/ffmpeg-explicitly-tag-h-264-as-bt-601-r...ng-unspecified

[marcorocchini]

thanks sneaker, please do you know if is there a special build of x264vfw that can encode changing the colormatrix?