Transcoding profiles¶

The profiles define the output format(s) that are acceptable for usage. With the various settings you can control how strict it is with transcoding or just copying the streams. An example profile:

[profile-webm]
container=webm
vcodec=vp9,vp8
vpolicy=only-mismatch
acodec=opus,vorbis
apolicy=only-mismatch
vbitrate=8M
vbitratemax=8M
abitrate=192k
abitratemax=1M

This profile will create files that are compatible with the webm specifications.

container¶

The container will define the output container format for the files, options are:

mkv
webm

vcodec / acodec¶

This defines what codec(s) are acceptable as output format. You can specify multiple codecs seperated by a comma.

If multiple codecs are specified it will always use the first codec in the list when transcoding is needed, the other codecs in the list are used for checking if the output is acceptable.

In the example above the video codec is defined as vp9,vp8, in that case if the input is an H.264 stream then it will transcode it to vp9 since H.264 is not an acceptable format and vp9 is the first specified format. If the input is an vp8 file it won’t transcode the file but just copy the stream to the new container (unless the vpolicy is changed)

Supported video codecs:

vp8
vp9
h264

Supported audio codecs:

mp3
aac
ac3
vorbis
opus

vpolicy / apolicy¶

The codec policy settings define what should happen if the input codec already matches the output codec options. The default setting is only-mismatch, in that case it will will copy the input stream directly into the output container without modification if the inputs match the output requirements.

The other option is always-transcode. In that mode it will always put the input stream through the encoder and decoder again, even if the codec matched. This might be necessary if the input files might contain weird things that aren’t supported on your player but still use the same codec. This option is not the default since transcoding the stream is way slower than just copying it.

vbitrate / abitrate¶

This specifies the output bitrate for the video and audio stream. This is only used when the file actually gets transcoded according the the policy specified. If this isn’t specified the defaults will be used for the specific codec.

vbitratemax / abitratemax¶

This is the maximum bitrate that the input file can have without it being forced to transcode. This can be used to override the policy defined when the input has a higher bitrate than can be played.

twopass¶

This can be set to enable twopass encoding. The default is false since this usually doesn’t help with the encoding quality but is way slower.

Codec specific options¶

Some codecs also have options of their own, prefixed with the codec name.