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TheoraVorbisEncodingGuide


Version 6 (modified by omniplex, 3 months ago) (diff)

fixed q:a range and added q:a to b:a formulae/examples

A Brief Theora and Vorbis Encoding Guide

The Theora video format, Vorbis audio format, and Ogg container formats were developed by Xiph.org as free and open-source media formats. ffmpeg can create these formats by using the external encoding libraries libtheora and libvorbis.

To use these encoders make sure your ffmpeg build has been compiled with --enable-libtheora and --enable-libvorbis, or refer to the output of ffmpeg -codecs. If you want to compile ffmpeg to support these encoders see the various FFmpeg Compilation Guides for detailed instructions.

libvorbis (-codec:a libvorbis) is recommended over the very experimental, native FFmpeg Vorbis audio encoder (-codec:a vorbis -strict experimental) since it does not provide comparable quality to libvorbis.

Note: More modern alternatives like VP9 can often provide better video quality at a lower bitrate. See the VP9 Encoding Guide.

Variable Bitrate (VBR)

ffmpeg -i input.mkv -codec:v libtheora -qscale:v 7 -codec:a libvorbis -qscale:a 5 output.ogv
  • -qscale:v – video quality. Range is 0–10, where 10 is highest quality. 5–7 is a good range to try. If you omit -qscale:v (or the alias -q:v) then ffmpeg will use the default -b:v 200k which will most likely provide a poor quality output, and libtheora may drop/skip frames if the bitrate is too low.
  • -qscale:a – audio quality. Range is -1.0 to 10.0, where 10.0 is highest quality. Default is -q:a 3 with a target of 112kbps. The formula 16×(q+4) is used below 4, 32×q is used below 8, and 64×(q-4) otherwise. Examples: 112=16×(3+4), 160=32×5, 200=32×6.25, 384=64×(10-4).

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