PortAudio.jl is a wrapper for libportaudio, which gives cross-platform access to audio devices. It is compatible with the types defined in SampledSignals.jl. It provides a PortAudioStream
type, which can be read from and written to.
The easiest way to open a source or sink is with the default PortAudioStream()
constructor, which will open a 2-in, 2-out stream to your system's default device(s). The constructor can also take the input and output channel counts as positional arguments, or a variety of other keyword arguments.
PortAudioStream(inchans=2, outchans=2; eltype=Float32, samplerate=48000Hz, latency=0.1, synced=false)
You can open a specific device by adding it as the first argument, either as a PortAudioDevice
instance or by name. You can also give separate names or devices if you want different input and output devices
PortAudioStream(device::PortAudioDevice, args...; kwargs...)
PortAudioStream(devname::AbstractString, args...; kwargs...)
You can get a list of your system's devices with the PortAudio.devices()
function:
julia> PortAudio.devices()
6-element Array{PortAudio.PortAudioDevice,1}:
PortAudio.PortAudioDevice("AirPlay","Core Audio",0,2,0)
PortAudio.PortAudioDevice("Built-in Microph","Core Audio",2,0,1)
PortAudio.PortAudioDevice("Built-in Output","Core Audio",0,2,2)
PortAudio.PortAudioDevice("JackRouter","Core Audio",2,2,3)
PortAudio.PortAudioDevice("After Effects 13.5","Core Audio",0,0,4)
PortAudio.PortAudioDevice("Built-In Aggregate","Core Audio",2,2,5)
The synced
keyword argument to PortAudioStream
controls whether the input and output ringbuffers are kept synchronized or not, which only effects duplex streams. It should be set to true
if you need consistent input-to-output latency. In a synchronized stream, the underlying PortAudio callback will only read and write to the buffers an equal number of frames. In a synchronized stream, the user must also read and write an equal number of frames to the stream. If it is only written to or read from, it will eventually block. This is why it is false
by default.
The PortAudioStream
type has source
and sink
fields which are of type PortAudioSource <: SampleSource
and PortAudioSink <: SampleSink
, respectively. are subtypes of SampleSource
and SampleSink
, respectively (from SampledSignals.jl). This means they support all the stream and buffer features defined there. For example, if you load SampledSignals with using SampledSignals
you can read 5 seconds to a buffer with buf = read(stream.source, 5s)
, regardless of the sample rate of the device.
PortAudio.jl also provides convenience wrappers around the PortAudioStream
type so you can read and write to it directly, e.g. write(stream, stream)
will set up a loopback that will read from the input and play it back on the output.
stream = PortAudioStream(2, 2)
try
# cancel with Ctrl-C
write(stream, stream)
finally
close(stream)
end
PortAudioStream(2, 2) do stream
write(stream, stream)
end
PortAudioStream("Built-in Microph", "Built-in Output") do stream
write(stream, stream)
end
julia> using PortAudio, SampledSignals, LibSndFile
julia> stream = PortAudioStream("Built-in Microph", 2, 0)
PortAudio.PortAudioStream{Float32,SIUnits.SIQuantity{Int64,0,0,-1,0,0,0,0,0,0}}
Samplerate: 48000 s⁻¹
Buffer Size: 4096 frames
2 channel source: "Built-in Microph"
julia> buf = read(stream, 10s)
480000-frame, 2-channel SampleBuf{Float32, 2, SIUnits.SIQuantity{Int64,0,0,-1,0,0,0,0,0,0}}
10.0 s at 48000 s⁻¹
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▁▄▂▃▅▃▂▄▃▂▂▁▁▂▂▁▁▄▃▁▁▄▂▁▁▁▄▃▁▁▃▃▁▁▁▁▁▁▁▁▄▄▄▄▄▂▂▂▁▃▃▁▃▄▂▁▁▁▁▃▃▂▁▁▁▁▁▁▃▃▂▂▁▃▃▃▁▁▁▁
julia> close(stream)
julia> save(joinpath(homedir(), "Desktop", "myvoice.ogg"), buf)