I'm trying to burn .ass subtitles onto a .webm, using
ffmpeg -i input.webm -vf ass=subtitles.ass output.webm but it shrinks from like 150MB to 9MB. How do I add the subtitles without losing quality ?
ffmpeg -i input.webm -vf ass=subtitles.ass -b:v 0 -crf 20 output.webm
The libvpx encoders for WebM, by default, perform Constrained Quality encoding, and use the bitrate as a ceiling. Default bitrate is 200 kbps. To remove bitrate ceiling, set bitrate to 0.
-crf controls the quality level.