bjarthur / WAV.jl

Julia package for working with WAV files

WAV.jl

This is a Julia package to read and write the WAV audio file format.

Installation

julia> Pkg.add("WAV")

Getting Started

WAV provides wavread and wavwrite commands to read and write WAV files. Here is an example to get you started. It generates some data, writes it to a file and then reads the data back.

julia> using WAV
julia> x = [0:7999]
julia> y = sin(2 * pi * x / 8000)
julia> wavwrite(y, "example.wav", Fs=8000)
julia> y, Fs = wavread("example.wav")

wavread

This function reads the samples from a WAV file. The samples are converted to floating point values in the range from -1.0 to 1.0 by default.

function wavread(io::IO; subrange=Any, format="double")
function wavread(filename::String; subrange=Any, format="double")

The available options, and the default values, are:

• format (default = double): changes the format of the returned samples. The string double returns double precision floating point values in the range -1.0 to 1.0. The string native returns the values as encoded in the file. The string size returns the number of samples in the file, rather than the actual samples.
• subrange (default = Any): controls which samples are returned. The default, Any returns all of the samples. Passing a number (Real), N, will return the first N samples of each channel. Passing a range (Range1{Real}), R, will return the samples in that range of each channel.

The returned values are:

• y: The acoustic samples; A matrix is returned for files that contain multiple channels.

• Fs: The sampling frequency

• nbits: The number of bits used to encode each sample

• extra: Any additional bytes used to encode the samples (is always None)

  The following functions are also defined to make this function compatible with MATLAB:

wavread(filename::String, fmt::String) = wavread(filename, format=fmt)
wavread(filename::String, N::Int) = wavread(filename, subrange=N)
wavread(filename::String, N::Range1{Int}) = wavread(filename, subrange=N)
wavread(filename::String, N::Int, fmt::String) = wavread(filename, subrange=N, format=fmt)
wavread(filename::String, N::Range1{Int}, fmt::String) = wavread(filename, subrange=N, format=fmt)

wavwrite

Writes samples to a RIFF/WAVE file io object. The io argument accepts either an IO object or a filename (String). The function assumes that the sample rate is 8 kHz and uses 16 bits to encode each sample. Both of these values can be changed with the options parameter. Each column of the data represents a different channel. Stereo files should contain two columns. The options are passed via an Options object (see the :ref:options page <options-module>).

function wavwrite(samples::Array, io::IO; Fs=8000, nbits=16, compression=WAVE_FORMAT_PCM)
function wavwrite(samples::Array, filename::String; Fs=8000, nbits=16, compression=WAVE_FORMAT_PCM)

The available options, and the default values, are:

• Fs (default = 8000): sampling frequency
• nbits (default = 16): number of bits used to encode each sample
• compression (default = WAV_FORMAT_PCM): controls the type of encoding used in the file

The type of the input array, samples, also affects the generated file. "Native" WAVE files are written when integers are passed into wavwrite. This means that the literal values are written into the file. The input ranges are as follows for integer samples.

N Bits	y Data Type	y Data Range	Output Format
8	uint8	0 <= y <= 255	uint8
16	int16	–32768 <= y <= +32767	int16
24	int32	–2^23 <= y <= 2^23 – 1	int32

If samples contains floating point values, the input data ranges are the following.

N Bits	y Data Type	y Data Range	Output Format
8	single or double	–1.0 <= y < +1.0	uint8
16	single or double	–1.0 <= y < +1.0	int16
24	single or double	–1.0 <= y < +1.0	int32
32	single or double	–1.0 <= y <= +1.0	single

The following functions are also defined to make this function compatible with MATLAB:

wavwrite(y::Array, f::Real, filename::String) = wavwrite(y, filename, Fs=f)
wavwrite(y::Array, f::Real, N::Real, filename::String) = wavwrite(y, filename, Fs=f, nbits=N)
wavwrite{T<:Integer}(y::Array{T}, io::IO) = wavwrite(y, io, nbits=sizeof(T)*8)
wavwrite{T<:Integer}(y::Array{T}, filename::String) = wavwrite(y, filename, nbits=sizeof(T)*8)
wavwrite(y::Array{Int32}, io::IO) = wavwrite(y, io, nbits=24)
wavwrite(y::Array{Int32}, filename::String) = wavwrite(y, filename, nbits=24)
wavwrite{T<:FloatingPoint}(y::Array{T}, io::IO) = wavwrite(y, io, nbits=sizeof(T)*8, compression=WAVE_FORMAT_IEEE_FLOAT)
wavwrite{T<:FloatingPoint}(y::Array{T}, filename::String) = wavwrite(y, filename, nbits=sizeof(T)*8, compression=WAVE_FORMAT_IEEE_FLOAT)