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I am trying to convert input.mp4 video to output.mkv using vp9 codec. I have install development version of ffmpeg via: brew install ffmpeg --devel.

ffmpeg -i input.mp4 -vcodec vp9 output.mkv

But I am getting error: Unknown encoder 'vp9' even the vp9 is included: ffmpeg -codecs

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    brew install ffmpeg --with-libvpx --with-opus
    – Joel Purra
    Feb 21, 2015 at 18:54
  • @JoelPurra Usage: brew install [options] formula|cask [...] Error: invalid option: --with-libvpx
    – Aaron Franke
    Dec 18, 2021 at 17:58

2 Answers 2

Reset to default
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The most basic command is:

ffmpeg -i input.mp4 -c:v libvpx-vp9 -c:a libopus output.webm

See FFmpeg Wiki: VP9 for more info.

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With my version of ffmpeg,

$ ffmpeg -version
ffmpeg version 2.3.3 Copyright (c) 2000-2014 the FFmpeg developers

the command looks like this

ffmpeg -y -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 1 -an -f webm /dev/null
ffmpeg    -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 2 -c:a opus -b:a 64k -f webm output.webm

i.e.

  • leave out the experimental flags
  • do a two pass encoding, because the first two seconds of the output are blurry otherwise. Doing a two pass encoding is also faster than single pass.
  • when doing 2 pass, you do not need to encode the audio in the first pass as @FrankGalligan noted in a comment

Single pass is/was broken, according to http://wiki.webmproject.org/vp9/known-issues

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  • Do not set -strict experimental. That was for older FFmpeg. When doing 2 pass, you do not need to encode the audio in the first pass. ffmpeg -y -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 1 -an -f webm /dev/null ffmpeg -i input.mkv -c:v libvpx-vp9 -b:v 2000k -pass 2 -c:a opus -b:a 64k -f webm output.webm
    – FrankGalligan
    Mar 3, 2015 at 1:32
  • Its odd no one uses cq. What is your reason to use webm vs mkv?
    – Michael Mantion
    May 26 at 16:01

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