AudioFormatWriter Class Reference

Writes samples to an audio file stream. More...

#include <juce_AudioFormatWriter.h>

Classes
class	ThreadedWriter
	Provides a FIFO for an AudioFormatWriter, allowing you to push incoming data into a buffer which will be flushed to disk by a background thread. More...
struct	WriteHelper
	Used by AudioFormatWriter subclasses to copy data to different formats. More...

Public Member Functions
virtual	~AudioFormatWriter ()
	Destructor.
const String &	getFormatName () const noexcept
	Returns a description of what type of format this is.
virtual bool	write (const int **samplesToWrite, int numSamples)=0
	Writes a set of samples to the audio stream.
virtual bool	flush ()
	Some formats may support a flush operation that makes sure the file is in a valid state before carrying on.
bool	writeFromAudioReader (AudioFormatReader &reader, int64 startSample, int64 numSamplesToRead)
	Reads a section of samples from an AudioFormatReader, and writes these to the output.
bool	writeFromAudioSource (AudioSource &source, int numSamplesToRead, int samplesPerBlock=2048)
	Reads some samples from an AudioSource, and writes these to the output.
bool	writeFromAudioSampleBuffer (const AudioBuffer< float > &source, int startSample, int numSamples)
	Writes some samples from an AudioBuffer.
bool	writeFromFloatArrays (const float *const *channels, int numChannels, int numSamples)
	Writes some samples from a set of float data channels.
double	getSampleRate () const noexcept
	Returns the sample rate being used.
int	getNumChannels () const noexcept
	Returns the number of channels being written.
int	getBitsPerSample () const noexcept
	Returns the bit-depth of the data being written.
bool	isFloatingPoint () const noexcept
	Returns true if it's a floating-point format, false if it's fixed-point.

Protected Member Functions
	AudioFormatWriter (OutputStream *destStream, const String &formatName, double sampleRate, unsigned int numberOfChannels, unsigned int bitsPerSample)
	Creates an AudioFormatWriter object.
	AudioFormatWriter (OutputStream *destStream, const String &formatName, double sampleRate, const AudioChannelSet &audioChannelLayout, unsigned int bitsPerSample)
	Creates an AudioFormatWriter object.

Protected Attributes
double	sampleRate
	The sample rate of the stream.
unsigned int	numChannels
	The number of channels being written to the stream.
unsigned int	bitsPerSample
	The bit depth of the file.
bool	usesFloatingPointData
	True if it's a floating-point format, false if it's fixed-point.
AudioChannelSet	channelLayout
	The audio channel layout that the writer should use.
OutputStream *	output
	The output stream for use by subclasses.

Detailed Description

Writes samples to an audio file stream.

A subclass that writes a specific type of audio format will be created by an AudioFormat object.

After creating one of these with the AudioFormat::createWriterFor() method you can call its write() method to store the samples, and then delete it.

See also

AudioFormat, AudioFormatReader

Constructor & Destructor Documentation

AudioFormatWriter() [1/2]

AudioFormatWriter::AudioFormatWriter ( OutputStream * destStream, const String & formatName, double sampleRate, unsigned int numberOfChannels, unsigned int bitsPerSample )

protected

Creates an AudioFormatWriter object.

Parameters

destStream	the stream to write to - this will be deleted by this object when it is no longer needed
formatName	the description that will be returned by the getFormatName() method
sampleRate	the sample rate to use - the base class just stores this value, it doesn't do anything with it
numberOfChannels	the number of channels to write - the base class just stores this value, it doesn't do anything with it
bitsPerSample	the bit depth of the stream - the base class just stores this value, it doesn't do anything with it

AudioFormatWriter() [2/2]

AudioFormatWriter::AudioFormatWriter ( OutputStream * destStream, const String & formatName, double sampleRate, const AudioChannelSet & audioChannelLayout, unsigned int bitsPerSample )

protected

Creates an AudioFormatWriter object.

Parameters

destStream	the stream to write to - this will be deleted by this object when it is no longer needed
formatName	the description that will be returned by the getFormatName() method
sampleRate	the sample rate to use - the base class just stores this value, it doesn't do anything with it
audioChannelLayout	the channel layout to use for the writer - the base class just stores this value, it doesn't do anything with it
bitsPerSample	the bit depth of the stream - the base class just stores this value, it doesn't do anything with it

~AudioFormatWriter()

virtual AudioFormatWriter::~AudioFormatWriter ( )

virtual

Destructor.

Member Function Documentation

getFormatName()

const String & AudioFormatWriter::getFormatName ( ) const

noexcept

Returns a description of what type of format this is.

E.g. "AIFF file"

write()

virtual bool AudioFormatWriter::write ( const int ** samplesToWrite, int numSamples )

pure virtual

Writes a set of samples to the audio stream.

Note that if you're trying to write the contents of an AudioBuffer, you can use writeFromAudioSampleBuffer().

Parameters

samplesToWrite

an array of arrays containing the sample data for each channel to write. This is a zero-terminated array of arrays, and can contain a different number of channels than the actual stream uses, and the writer should do its best to cope with this. If the format is fixed-point, each channel will be formatted as an array of signed integers using the full 32-bit range -0x80000000 to 0x7fffffff, regardless of the source's bit-depth. If it is a floating-point format, you should treat the arrays as arrays of floats, and just cast it to an (int**) to pass it into the method.

numSamples

the number of samples to write

flush()

virtual bool AudioFormatWriter::flush ( )

virtual

Some formats may support a flush operation that makes sure the file is in a valid state before carrying on.

If supported, this means that by calling flush periodically when writing data to a large file, then it should still be left in a readable state if your program crashes. It goes without saying that this method must be called from the same thread that's calling write()! If the format supports flushing and the operation succeeds, this returns true.

writeFromAudioReader()

bool AudioFormatWriter::writeFromAudioReader	(	AudioFormatReader &	reader,
		int64	startSample,
		int64	numSamplesToRead )

Reads a section of samples from an AudioFormatReader, and writes these to the output.

This will take care of any floating-point conversion that's required to convert between the two formats. It won't deal with sample-rate conversion, though.

If numSamplesToRead < 0, it will write the entire length of the reader.

Returns

false if it can't read or write properly during the operation

writeFromAudioSource()

bool AudioFormatWriter::writeFromAudioSource	(	AudioSource &	source,
		int	numSamplesToRead,
		int	samplesPerBlock = 2048 )

Reads some samples from an AudioSource, and writes these to the output.

The source must already have been initialised with the AudioSource::prepareToPlay() method

Parameters

source	the source to read from
numSamplesToRead	total number of samples to read and write
samplesPerBlock	the maximum number of samples to fetch from the source

Returns

false if it can't read or write properly during the operation

writeFromAudioSampleBuffer()

bool AudioFormatWriter::writeFromAudioSampleBuffer	(	const AudioBuffer< float > &	source,
		int	startSample,
		int	numSamples )

Writes some samples from an AudioBuffer.

writeFromFloatArrays()

bool AudioFormatWriter::writeFromFloatArrays	(	const float *const *	channels,
		int	numChannels,
		int	numSamples )

Writes some samples from a set of float data channels.

getSampleRate()

double AudioFormatWriter::getSampleRate ( ) const

noexcept

Returns the sample rate being used.

getNumChannels()

int AudioFormatWriter::getNumChannels ( ) const

noexcept

Returns the number of channels being written.

getBitsPerSample()

int AudioFormatWriter::getBitsPerSample ( ) const

noexcept

Returns the bit-depth of the data being written.

isFloatingPoint()

bool AudioFormatWriter::isFloatingPoint ( ) const

noexcept

Returns true if it's a floating-point format, false if it's fixed-point.

Member Data Documentation

sampleRate

double AudioFormatWriter::sampleRate

protected

The sample rate of the stream.

numChannels

unsigned int AudioFormatWriter::numChannels

protected

The number of channels being written to the stream.

bitsPerSample

unsigned int AudioFormatWriter::bitsPerSample

protected

The bit depth of the file.

usesFloatingPointData

bool AudioFormatWriter::usesFloatingPointData

protected

True if it's a floating-point format, false if it's fixed-point.

channelLayout

AudioChannelSet AudioFormatWriter::channelLayout

protected

The audio channel layout that the writer should use.

output

OutputStream* AudioFormatWriter::output

protected

The output stream for use by subclasses.

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The documentation for this class was generated from the following file:

• juce_AudioFormatWriter.h