CODEWITHSUNDEEP
macosffmpeg
wetjosh
wetjosh

Reputation: 6398

FFmpeg screen recording in grayscale to reduce file size?

First off, I am unable to capture the screen of my Mac in grayscale. I've tried various combinations of -pix_fmt gray (for the input, for the output, and for both) but they never turn out grayscale.

Secondly, assuming I figure out how to do it, is it actually a viable option for reducing file size? I was surprised that reducing the frame rate (-r) did not affect file size (though -size did).

ffmpeg -f avfoundation -pix_fmt gray -s 1440x900 -i 1 \
-pix_fmt gray -r 30 -preset ultrafast -b:v 5000k -t 5 out.mov

Upvotes: 0

Views: 536

Answers (1)

Tarwin Stroh-Spijer
Tarwin Stroh-Spijer

Reputation: 353

Recording in grayscale will reduce file size a little, depending on the colorspace you are recording to.

Most MPEG video formats by default will using Chroma Subsampling (https://www.wikiwand.com/en/Chroma_subsampling), as 4:2:0.

I'm not aware of which formats record luminance only (grayscale). Even if they are recording grayscale in a 4:2:0 space you may save a small amount of space because the temporal information about chroma will be very low.

Upvotes: 3

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