GIF to WebM with ffmpeg

webm.md

Grab ffmpeg from https://www.ffmpeg.org/download.html

The most trivial operation would be converting gifs:

ffmpeg -i your_gif.gif -c:v libvpx-vp9 -crf 12 -b:v 500K output.webm

• -crf values can go from 4 to 63. Lower values mean better quality.
• -b:v is the maximum allowed bitrate. Higher means better quality.

To convert a part of a video file:

ffmpeg -i your_video.mkv -ss 00:00:10.000 -to 00:00:20.000 -c:v libvpx -crf 4 -b:v 1500K -vf scale=640:-1 -an output.webm

• -ss is the start position in number of seconds, or in hh:mm:ss[.xxx] format. You can get it using your video player (Ctrl-G in MPC-HC).
• -to is the end position.
• -vf scale=640:-1 sets the width to 640px. The height will be calculated automatically according to the aspect ratio of the input.
• -an disables audio. 4chan will reject your files if they contain audio streams.

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• Another encoding guide: https://trac.ffmpeg.org/wiki/vpxEncodingGuide
• ffmpeg documentation: https://www.ffmpeg.org/ffmpeg.html

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Just a tip since I hit this on a search, the first command may fail with the error:

Transparency encoding with auto_alt_ref does not work

This can be fixed by updating the command to use libvpx-vp9:

ffmpeg -i your_gif.gif -c:v libvpx-vp9 -crf 12 -b:v 500K output.webm

Ah, thanks for the tip! Edited the op.