raop-rtsp-server

An attempt to create a RAOP (AirTunes) server in Node.js.

This project is highly work-in-progress - use it at your own risk!

Known compatibility issues:

• Currently this module will only compile on Node.js v0.10. Hopefully this will be fixed soon.

Installation

For standalone usage, run:

npm install --global raop-rtsp-server

For programmatic usage, run:

npm install raop-rtsp-server

CLI usage

If the speaker module can compile on your system (comes bundled with this module), you should just be able to start the server without any arguments:

raop-rtsp-server

If you'd rather pipe the PCM audio to another player, you can do so using the --stdout argument:

raop-rtsp-server --stdout | sox -traw -L -c2 -r44100 -b16 -e signed-integer - -tcoreaudio

See the Tips section below on how to install and use sox

Debugging

To run in debug mode, use the DEBUG environment variable:

DEBUG=* raop-rtsp-server

Or the less chatty:

DEBUG=raop-rtsp-server raop-rtsp-server

Programmatic usage

The module can also be access programmatically:

var server = require('raop-rtsp-server')

server.sessions.on('new', function (session) {
  session.on('data', function (chunk) {
    console.log('received %d audio bytes on session %s', chunk.length, session.id)
  })

  session.on('volume', function (volume) {
    console.log('the client changed the volume to %d dB', volume)
  })
})

server.start({ name: 'NodeTunes' })

The server.start() function takes an optional options object:

• name - The name that the RAOP server (this will be shown on your iDevices). Defaults to raop-rtsp-server
• port - The port that the server should listen on. Defaults to 5000

Session

The session object emitted by the new event is a readable stream and will output raw PCM audio data.

Properties

• volume - A float between 0 and 1 representing the current volume level (0 being muted and 1 being full volume)
• volumeDb - A float value representing the audio attenuation in dB. It ranges from -30 (lowest) to 0 (highest). A special number -144 represents mute.

Events

Besides the normal readable stream API, the session also emits the following events:

volume

Emitted when ever the client changes the volume. The value emitted is the volume as a float value representing the audio attenuation in dB. It ranges from -30 (lowest) to 0 (highest). A special number -144 represents mute.

Tips

If using this module to output raw PCM audio to STDOUT, I've found the following useful:

I've tried quite a few different audio players but I've only managed to get sox to play back to PCM audio.

Install via Homebrew:

brew install sox

For sox to be able to interpret the raw ALAC audio data, you need to help it a little. These are the command line arguments given in the example above:

• -t raw - Set input type to raw. This means that sox shouldn't expect any headers in the data - just raw audio
• -L - The audio data is formatted using native byte ordering, which is little endian on Intel CPU's. Your system might use -B for big endian
• -c 2 - Use 2 audio channels
• -r 44100 - Use a 44.1khz sample rate
• -b 16 - Use a bit-depth of 16
• -e signed-integer - The audio encoding type
• - - Set input source to STDIN
• -t coreaudio - Set output type to coreaudio (your system might differ, but this must always come after your input source)

FFmpeg should also be able to parse PCM audio if you like that program better.

License

MIT