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Audio
The other-transcode.rb tool automatically selects the first audio track in the input media as the main track and determines the output format based on the number of channels in that track.
Use the --main-audio option to select a different track. For example, to select the second track:
other-transcode.rb --main-audio 2 C:\Rips\Movie.mkv
The channel "width" of the main audio track supports surround audio. But that width can be restricted to stereo like this:
other-transcode.rb --main-audio 1=stereo C:\Rips\Movie.mkv
To disable audio output entirely, use 0 as the track number:
other-transcode.rb --main-audio 0 C:\Rips\Movie.mkv
Other audio tracks can be added by track number, language or title.
For example, to add the third audio track:
other-transcode.rb --add-audio 3 C:\Rips\Movie.mkv
To add, for example, all English-language tracks, use the three-letter code, in ISO 639-2 format, for that language:
other-transcode.rb --add-audio eng C:\Rips\Movie.mkv
If an audio track is titled "Director Commentary" for example, it can be added with a case-insensitive sub-string comparison like this:
other-transcode.rb --add-audio commentary C:\Rips\Movie.mkv
The channel "width" of added audio tracks is restricted to stereo audio. But that can be "widened" to allow surround like this:
other-transcode.rb --add-audio 3=surround C:\Rips\Movie.mkv
If multiple --add-audio options would add the same track in the same width, then that track is only added once.
And it's possible to duplicate an audio track in a different width. For example, to duplicate the main audio track in stereo format:
other-transcode.rb --add-audio 1=stereo C:\Rips\Movie.mkv
However, if the main audio track is already in stereo format, it won't be duplicated.
The default audio output formats are AC-3 for surround tracks and AAC for stereo and mono tracks. Use the --surround-bitrate and --stereo-bitrate options to change transcoding bitrates.
If the input track is already in AC-3 or non-surround AAC format, then it's usually copied rather than transcoded to the output.
Dolby Digital Plus (Enhanced AC-3) audio encoding for all tracks is available via the --eac3 option.