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2f9fa0da6f
Other small fixes: - Fixed typo in README - Fixed `oggenc2` using `-q` instead of `-Q` to mean "quiet" Fixes #170
106 lines
4.7 KiB
Markdown
106 lines
4.7 KiB
Markdown
# Transcoding
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Transcoding is the process of converting from one audio format to another. This
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allows for streaming of formats that wouldn't be streamable otherwise, or
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reducing the quality of an audio file to allow a decent streaming for clients
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with limited bandwidth, such as the ones running on a mobile connection.
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Transcoding in _Supysonic_ is achieved through the use of third-party
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command-line programs. _Supysonic_ isn't bundled with such programs, and you are
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left to choose which one you want to use.
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If you want to use transcoding but your client doesn't allow you to do so, you
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can force _Supysonic_ to transcode for that client by going to your profile page
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on the web interface.
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## Configuration
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Configuration of transcoders is done on the `[transcoding]` section of the
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[configuration file](configuration.md).
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Transcoding can be done by one single program which is able to convert from one
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format directly to another one, or by two programs: a decoder and an encoder.
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All these are defined by the following variables:
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* `transcoder_EXT_EXT`
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* `decoder_EXT`
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* `encoder_EXT`
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* `trancoder`
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* `decoder`
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* `encoder`
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* `default_transcode_target`
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where `EXT` is the lowercase file extension of the matching audio format.
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`transcoder`s variables have two extensions: the first one is the source
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extension, and the second one is the extension to convert to. The same way,
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`decoder`s extension is the source extension, and `encoder`s extension is the
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extension to convert to.
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Notice that all of them have a version without extension. Those are generic
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versions. The programs defined with these variables should be able to
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transcode/decode/encode any format. For that reason, we suggest you don't use
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these if you want to keep control over the available transcoders.
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_Supysonic_ will take the first available transcoding configuration in the
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following order:
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1. specific transcoder
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2. specific decoder / specific encoder
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3. generic decoder / generic encoder (with the possibility to use a generic
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decoder with a specific encoder, and vice-versa)
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4. generic transcoder
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All the variables should be set to the command-line used to run the converter
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program. The command-lines can include the following fields:
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* `%srcpath`: path to the original file to transcode
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* `%srcfmt`: extension of the original file
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* `%outfmt`: extension of the resulting file
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* `%outrate`: bitrate of the resulting file
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* `%title`: title of the file to transcode
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* `%album`: album name of the file to transcode
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* `%artist`: artist name of the file to transcode
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* `%tracknumber`: track number of the file to transcode
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* `%totaltracks`: number of tracks in the album of the file to transcode
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* `%discnumber`: disc number of the file to transcode
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* `%genre`: genre of the file to transcode (not always available, defaults to "")
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* `%year`: year of the file to transcode (not always available, defaults to "")
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One final note: the original file should be provided as an argument of
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transcoders and decoders. All transcoders, decoders and encoders should write
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to standard output, and encoders should read from standard input.
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The value of `default_transcode_target` will be used as output format when a
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client requests a bitrate lower than the original file and no specific format.
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## Suggested configuration
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Here is an example configuration that you could use. This is provided as-is,
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and some configurations haven't been tested.
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Basic configuration:
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```ini
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[transcoding]
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transcoder_mp3_mp3 = lame --quiet --mp3input -b %outrate %srcpath -
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transcoder = ffmpeg -i %srcpath -ab %outratek -v 0 -f %outfmt -
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decoder_mp3 = mpg123 --quiet -w - %srcpath
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decoder_ogg = oggdec -o %srcpath
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decoder_flac = flac -d -c -s %srcpath
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encoder_mp3 = lame --quiet -b %outrate - -
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encoder_ogg = oggenc2 -Q -M %outrate -
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default_transcode_target = mp3
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```
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To include track metadata in the transcoded stream:
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```ini
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[transcoding]
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transcoder_mp3_mp3 = lame --quiet --mp3input -b %outrate --tt %title --tl %album --ta %artist --tn %tracknumber/%totaltracks --tv TPOS=%discnumber --tg %genre --ty %year --add-id3v2 %srcpath -
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transcoder = ffmpeg -i %srcpath -ab %outratek -v 0 -metadata title=%title -metadata album=%album -metadata author=%artist -metadata track=%tracknumber/%totaltracks -metadata disc=%discnumber -metadata genre=%genre -metadata date=%year -f %outfmt -
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decoder_mp3 = mpg123 --quiet -w - %srcpath
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decoder_ogg = oggdec -o %srcpath
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decoder_flac = flac -d -c -s %srcpath
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encoder_mp3 = lame --quiet -b %outrate --tt %title --tl %album --ta %artist --tn %tracknumber/%totaltracks --tv TPOS=%discnumber --tg %genre --ty %year --add-id3v2 - -
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encoder_ogg = oggenc2 -Q -M %outrate -t %title -l %album -a %artist -N %tracknumber -c TOTALTRACKS=%totaltracks -c DISCNUMBER=%discnumber -G %genre -d %year -
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default_transcode_target = mp3
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```
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