2

I need to reduce the file size of an mp4 video. I don't need color information at all but pixel brightness resolution must be preserved. Videos consist of white background with a few (important) black dots of about 5px diameter. I am confused about what the best method/output would be.

2

Without knowing the video properties, my generic answer is

ffmpeg -i in.mp4 -vf geq=lum='p(X,Y)':cb=128:cr=128 out.mp4

This will reset the color information, but pass the luma plane intact. Add -crf 0 for truly lossless re-encoding.


This is the faster way,

ffmpeg -i in.mp4 -vf extractplanes=y,format=yuv420p out.mp4

The luma plane is extracted, and then neutral chroma planes are added in the pixel format conversion. This 2nd step is added because otherwise ffmpeg will auto-convert pixel format to yuv444 which isn't widely compatible.

2
  • Awesome, that works. Is this the quickest way? If not, what information would need to know for a faster/better solution? – Stefan Popp Mar 18 '18 at 0:37
  • There's one potentially quicker way but I have to check whether it alters the luma. – Gyan Mar 18 '18 at 8:18
1

Much faster solution: ffmpeg -i in.mp4 -vf extractplanes=y out.mp4

2
  • What makes that faster? Can you explain the -vf option so that others can solve their own problems in the future? – Michael Liebman Mar 18 '18 at 22:38
  • User wants luma plane only, so this command do that efficiently. Also geq filter is GPL and slow in almost any scenario. – Paul B. Mahol Mar 19 '18 at 8:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.