PortAudio.jl/notes/file_api.md

Some possible API concepts for dealing with files

Notes

• requires libflac for flac decoding

Use Cases

• Play a file through the speakers
• Use a file as input to an AudioNode for processing
• Read a file into an array
• Write an array into a file
• Write the output of an AudioNode to a file

IOStream API

• users use standard julia "open" function to create an IOStream object
• FilePlayer <: AudioNode takes an IOStream and uses sf_open_fd to open and play
• play(io::IOStream) creates a FilePlayer and plays it (just like ArrayPlayer)
• FileStream

Play a file through the speakers

sndfile = open("myfile.wav")
play(sndfile)
close(sndfile)

Use a file as input to an AudioNode for processing

sndfile = open("myfile.wav")
# maybe FilePlayer also takes a string input for convenience
node = FilePlayer(sndfile)
mixer = AudioMixer([node])
# etc.

Read a file into an array

# TODO

Write an array into a file

# TODO

Write the output of an AudioNode to a file

node = SinOsc(440)
# ???

Separate Open Function API

• users use an explicit af_open function to open sound files
• af_open takes mode arguments just like the regular julia open function
• af_open returns a AudioFile instance.

Play a file through the speakers

sndfile = af_open("myfile.wav")
play(sndfile)
close(sndfile)

or

play("myfile.wav")

Use a file as input to an AudioNode for processing

sndfile = af_open("myfile.wav")
# FilePlayer also can take a string filename for convenience
node = FilePlayer(sndfile)
mixer = AudioMixer([node])
# etc.

Read a file into an array

sndfile = af_open("myfile.wav")
vec = read(sndfile) # takes an optional arg for number of frames to read
close(sndfile)

Write an array into a file

sndfile = af_open("myfile.wav", "w") #TODO: need to specify format
vec = rand(Float32, 441000) # 10 seconds of noise
write(sndfile, vec)
close(sndfile)

Write the output of an AudioNode to a file

sndfile = af_open("myfile.wav", "w") #TODO: need to specify format
node = SinOsc(440)
write(sndfile, node, 44100) # record 1 second, optional block_size
# note that write() can handle sample depth conversions, and render() is
# called with the sampling rate of the file
close(sndfile)