81 lines
2.0 KiB
Markdown
81 lines
2.0 KiB
Markdown
# racket-audio
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Integration of common audio libraries in Racket.
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The package contains decoder, player and encoder bindings. Playback uses the
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existing audio player modules. Encoding is provided by `audio-encoder.rkt` with
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Opus and FLAC backends.
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## Native dependencies
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For playback and decoding, install the native libraries used by the selected
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backends:
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- libao
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- libFLAC
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- mpg123
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- FFmpeg libraries, including libavutil, libavcodec, libavformat and
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libswresample
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For encoding, also install:
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- libopusenc
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- libopus
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- libogg
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- TagLib with the C binding, usually provided as `taglib` / `taglib_c`
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The Opus encoder backend uses libopusenc directly. The FLAC encoder backend
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uses libFLAC directly. FLAC sample-rate conversion uses the existing FFmpeg
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swresample layer. Metadata and cover-art copying use the TagLib wrapper; the
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public `taglib.rkt` API also supports read-write tag editing.
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## macOS
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Using Homebrew, install the native libraries before using the package:
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```sh
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brew install libao
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brew install flac
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brew install mpg123
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brew install ffmpeg
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brew install opus
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brew install libopusenc
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brew install taglib
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```
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Some Homebrew installations provide FFmpeg as `ffmpeg`; older local setups may
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use `ffmpeg-full`.
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## Encoder examples
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Encode to Opus:
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```racket
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(require "audio-encoder.rkt")
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(audio-encode "input.flac"
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"output.opus"
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(hash 'bitrate 224000
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'vbr? #t
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'complexity 10)
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#:encoder 'opus)
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```
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Encode 96 kHz FLAC to 48 kHz FLAC:
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```racket
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(audio-encode "input-96k.flac"
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"output-48k.flac"
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(hash 'sample-rate 48000
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'bits-per-sample 24
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'compression-level 8)
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#:encoder 'flac)
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```
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A small test wrapper is available in `encoder-test.rkt`:
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```sh
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racket encoder-test.rkt --encoder opus --input input.flac --output output.opus --bitrate-kbps 224
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racket encoder-test.rkt --encoder flac --input input-96k.flac --output output-48k.flac --sample-rate 48000
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```
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