PortAudio.jl

This is a Julia interface to PortAudio. It is currently under heavy development. The API could change, there will be bugs, there are important missing features.

If you want to try it anyways, from your julia console:

julia> Pkg.clone("https://github.com/ssfrr/PortAudio.jl.git")
julia> Pkg.build("PortAudio")

Basic Array Playback

Arrays in various formats can be played through your soundcard. Currently the native format that is delivered to the PortAudio backend is Float32 in the range of [-1, 1]. Arrays in other sizes of float are converted. Arrays in Signed or Unsigned Integer types are scaled so that the full range is mapped to [-1, 1] floating point values.

To play a 1-second burst of noise:

julia> v = rand(44100) * 0.1
julia> play(v)

AudioNodes

In addition to the basic play function you can create more complex networks of AudioNodes in a render chain. In fact, when using the basic play to play an Array, behind the scenes an instance of the ArrayPlayer type is created and added to the master AudioMixer inputs.

To explictly do the same as above:

julia> v = rand(44100) * 0.1
julia> player = ArrayPlayer(v)
julia> play(player)

To generate 2 sin tones:

julia> osc1 = SinOsc(440)
julia> osc2 = SinOsc(660)
julia> play(osc1)
julia> play(osc2)

All AudioNodes should implement a render function that can be called to retreive the next block of audio.

AudioStreams

AudioStreams represent a destination for audio, such as the sound card. The play function attaches AudioNodes to the default stream unless a stream is given as the 2nd argument.

AudioStream is an abstract type, which currently has a PortAudioStream subtype that writes to the sound card, and a TestAudioStream that is used in the unit tests.

Currently only 1 stream at a time is supported so there's no reason to provide an explicit stream to the play function. The stream has a root mixer field which is an instance of the AudioMixer type, so that multiple AudioNodes can be heard at the same time. Whenever a new frame of audio is needed by the sound card, the stream calls the render method on the root audio mixer, which will in turn call the render methods on any input AudioNodes that are set up as inputs.