An AudioFormatReader that uses a background thread to pre-read data from another reader. More...

#include <juce_BufferingAudioFormatReader.h>

Inheritance diagram for juce::BufferingAudioReader:

Collaboration diagram for juce::BufferingAudioReader:

[legend]

Classes
struct	BufferedBlock

Public Member Functions
	BufferingAudioReader (AudioFormatReader *sourceReader, TimeSliceThread &timeSliceThread, int samplesToBuffer)
	Creates a reader. More...

	~BufferingAudioReader () override

virtual AudioChannelSet	getChannelLayout ()
	Get the channel layout of the audio stream. More...

const String &	getFormatName () const noexcept
	Returns a description of what type of format this is. More...

void	read (AudioBuffer< float > *buffer, int startSampleInDestBuffer, int numSamples, int64 readerStartSample, bool useReaderLeftChan, bool useReaderRightChan)
	Fills a section of an AudioBuffer from this reader. More...

bool	read (float const destChannels, int numDestChannels, int64 startSampleInSource, int numSamplesToRead)
	Reads samples from the stream. More...

bool	read (int const destChannels, int numDestChannels, int64 startSampleInSource, int numSamplesToRead, bool fillLeftoverChannelsWithCopies)
	Reads samples from the stream. More...

virtual void	readMaxLevels (int64 startSample, int64 numSamples, float &lowestLeft, float &highestLeft, float &lowestRight, float &highestRight)
	Finds the highest and lowest sample levels from a section of the audio stream. More...

virtual void	readMaxLevels (int64 startSample, int64 numSamples, Range< float > *results, int numChannelsToRead)
	Finds the highest and lowest sample levels from a section of the audio stream. More...

bool	readSamples (int **destSamples, int numDestChannels, int startOffsetInDestBuffer, int64 startSampleInFile, int numSamples) override
	Subclasses must implement this method to perform the low-level read operation. More...

int64	searchForLevel (int64 startSample, int64 numSamplesToSearch, double magnitudeRangeMinimum, double magnitudeRangeMaximum, int minimumConsecutiveSamples)
	Scans the source looking for a sample whose magnitude is in a specified range. More...

void	setReadTimeout (int timeoutMilliseconds) noexcept
	Sets a number of milliseconds that the reader can block for in its readSamples() method before giving up and returning silence. More...

Public Attributes
unsigned int	bitsPerSample = 0
	The number of bits per sample, e.g. More...

InputStream *	input
	The input stream, for use by subclasses. More...

int64	lengthInSamples = 0
	The total number of samples in the audio stream. More...

StringPairArray	metadataValues
	A set of metadata values that the reader has pulled out of the stream. More...

unsigned int	numChannels = 0
	The total number of channels in the audio stream. More...

double	sampleRate = 0
	The sample-rate of the stream. More...

bool	usesFloatingPointData = false
	Indicates whether the data is floating-point or fixed. More...

Static Protected Member Functions
static void	clearSamplesBeyondAvailableLength (int **destChannels, int numDestChannels, int startOffsetInDestBuffer, int64 startSampleInFile, int &numSamples, int64 fileLengthInSamples)
	Used by AudioFormatReader subclasses to clear any parts of the data blocks that lie beyond the end of their available length. More...

Private Member Functions
BufferedBlock *	getBlockContaining (int64 pos) const noexcept

bool	readNextBufferChunk ()

int	useTimeSlice () override
	Called back by a TimeSliceThread. More...

Private Attributes
OwnedArray< BufferedBlock >	blocks

String	formatName

CriticalSection	lock

Time	nextCallTime

std::atomic< int64 >	nextReadPosition { 0 }

const int	numBlocks

std::unique_ptr< AudioFormatReader >	source

TimeSliceThread &	thread

int	timeoutMs = 0

Static Private Attributes
static constexpr int	samplesPerBlock = 32768

Detailed Description

An AudioFormatReader that uses a background thread to pre-read data from another reader.

See also: AudioFormatReader

@tags{Audio}

Constructor & Destructor Documentation

◆ BufferingAudioReader()

juce::BufferingAudioReader::BufferingAudioReader	(	AudioFormatReader *	sourceReader,
		TimeSliceThread &	timeSliceThread,
		int	samplesToBuffer
	)

Creates a reader.

Parameters

sourceReader	the source reader to wrap. This BufferingAudioReader takes ownership of this object and will delete it later when no longer needed
timeSliceThread	the thread that should be used to do the background reading. Make sure that the thread you supply is running, and won't be deleted while the reader object still exists.
samplesToBuffer	the total number of samples to buffer ahead.

◆ ~BufferingAudioReader()

juce::BufferingAudioReader::~BufferingAudioReader ( )

override

Member Function Documentation

◆ clearSamplesBeyondAvailableLength()

static void juce::AudioFormatReader::clearSamplesBeyondAvailableLength	(	int **	destChannels,
		int	numDestChannels,
		int	startOffsetInDestBuffer,
		int64	startSampleInFile,
		int &	numSamples,
		int64	fileLengthInSamples
	)

inlinestaticprotectedinherited

Used by AudioFormatReader subclasses to clear any parts of the data blocks that lie beyond the end of their available length.

References int(), jassertfalse, and juce::zeromem().

◆ getBlockContaining()

BufferedBlock* juce::BufferingAudioReader::getBlockContaining ( int64 pos ) const

privatenoexcept

◆ getChannelLayout()

virtual AudioChannelSet juce::AudioFormatReader::getChannelLayout ( )

virtualinherited

Get the channel layout of the audio stream.

◆ getFormatName()

const String& juce::AudioFormatReader::getFormatName ( ) const

inlinenoexceptinherited

Returns a description of what type of format this is.

E.g. "AIFF"

◆ read() [1/3]

void juce::AudioFormatReader::read	(	AudioBuffer< float > *	buffer,
		int	startSampleInDestBuffer,
		int	numSamples,
		int64	readerStartSample,
		bool	useReaderLeftChan,
		bool	useReaderRightChan
	)

inherited

Fills a section of an AudioBuffer from this reader.

This will convert the reader's fixed- or floating-point data to the buffer's floating-point format, and will try to intelligently cope with mismatches between the number of channels in the reader and the buffer.

◆ read() [2/3]

bool juce::AudioFormatReader::read	(	float const	destChannels,
		int	numDestChannels,
		int64	startSampleInSource,
		int	numSamplesToRead
	)

inherited

Reads samples from the stream.

Parameters

destChannels	an array of float buffers into which the sample data for each channel will be written. Channels that aren't needed can be null
numDestChannels	the number of array elements in the destChannels array
startSampleInSource	the position in the audio file or stream at which the samples should be read, as a number of samples from the start of the stream. It's ok for this to be beyond the start or end of the available data - any samples that are out-of-range will be returned as zeros.
numSamplesToRead	the number of samples to read. If this is greater than the number of samples that the file or stream contains. the result will be padded with zeros

Returns: true if the operation succeeded, false if there was an error. Note that reading sections of data beyond the extent of the stream isn't an error - the reader should just return zeros for these regions

See also: readMaxLevels

◆ read() [3/3]

bool juce::AudioFormatReader::read	(	int const	destChannels,
		int	numDestChannels,
		int64	startSampleInSource,
		int	numSamplesToRead,
		bool	fillLeftoverChannelsWithCopies
	)

inherited

Reads samples from the stream.

Parameters

destChannels	an array of buffers into which the sample data for each channel will be written. If the format is fixed-point, each channel will be written as an array of 32-bit signed integers using the full range -0x80000000 to 0x7fffffff, regardless of the source's bit-depth. If it is a floating-point format, you should cast the resulting array to a (float**) to get the values (in the range -1.0 to 1.0 or beyond) If the format is stereo, then destChannels[0] is the left channel data, and destChannels[1] is the right channel. The numDestChannels parameter indicates how many pointers this array contains, but some of these pointers can be null if you don't want to read data for some of the channels
numDestChannels	the number of array elements in the destChannels array
startSampleInSource	the position in the audio file or stream at which the samples should be read, as a number of samples from the start of the stream. It's ok for this to be beyond the start or end of the available data - any samples that are out-of-range will be returned as zeros.
numSamplesToRead	the number of samples to read. If this is greater than the number of samples that the file or stream contains. the result will be padded with zeros
fillLeftoverChannelsWithCopies	if true, this indicates that if there's no source data available for some of the channels that you pass in, then they should be filled with copies of valid source channels. E.g. if you're reading a mono file and you pass 2 channels to this method, then if fillLeftoverChannelsWithCopies is true, both destination channels will be filled with the same data from the file's single channel. If fillLeftoverChannelsWithCopies was false, then only the first channel would be filled with the file's contents, and the second would be cleared. If there are many channels, e.g. you try to read 4 channels from a stereo file, then the last 3 would all end up with copies of the same data.

Returns: true if the operation succeeded, false if there was an error. Note that reading sections of data beyond the extent of the stream isn't an error - the reader should just return zeros for these regions

See also: readMaxLevels

◆ readMaxLevels() [1/2]

virtual void juce::AudioFormatReader::readMaxLevels	(	int64	startSample,
		int64	numSamples,
		float &	lowestLeft,
		float &	highestLeft,
		float &	lowestRight,
		float &	highestRight
	)

virtualinherited

Finds the highest and lowest sample levels from a section of the audio stream.

This will read a block of samples from the stream, and measure the highest and lowest sample levels from the channels in that section, returning these as normalised floating-point levels.

Parameters

startSample	the offset into the audio stream to start reading from. It's ok for this to be beyond the start or end of the stream.
numSamples	how many samples to read
lowestLeft	on return, this is the lowest absolute sample from the left channel
highestLeft	on return, this is the highest absolute sample from the left channel
lowestRight	on return, this is the lowest absolute sample from the right channel (if there is one)
highestRight	on return, this is the highest absolute sample from the right channel (if there is one)

See also: read

◆ readMaxLevels() [2/2]

virtual void juce::AudioFormatReader::readMaxLevels	(	int64	startSample,
		int64	numSamples,
		Range< float > *	results,
		int	numChannelsToRead
	)

virtualinherited

Finds the highest and lowest sample levels from a section of the audio stream.

This will read a block of samples from the stream, and measure the highest and lowest sample levels from the channels in that section, returning these as normalised floating-point levels.

Parameters

startSample	the offset into the audio stream to start reading from. It's ok for this to be beyond the start or end of the stream.
numSamples	how many samples to read
results	this array will be filled with Range values for each channel. The array must contain numChannels elements.
numChannelsToRead	the number of channels of data to scan. This must be more than zero, but not more than the total number of channels that the reader contains

See also: read

Reimplemented in juce::AudioSubsectionReader.

◆ readNextBufferChunk()

bool juce::BufferingAudioReader::readNextBufferChunk ( )

private

◆ readSamples()

bool juce::BufferingAudioReader::readSamples	(	int **	destChannels,
		int	numDestChannels,
		int	startOffsetInDestBuffer,
		int64	startSampleInFile,
		int	numSamples
	)

overridevirtual

Subclasses must implement this method to perform the low-level read operation.

Callers should use read() instead of calling this directly.

Parameters

destChannels	the array of destination buffers to fill. Some of these pointers may be null
numDestChannels	the number of items in the destChannels array. This value is guaranteed not to be greater than the number of channels that this reader object contains
startOffsetInDestBuffer	the number of samples from the start of the dest data at which to begin writing
startSampleInFile	the number of samples into the source data at which to begin reading. This value is guaranteed to be >= 0.
numSamples	the number of samples to read

Implements juce::AudioFormatReader.

◆ searchForLevel()

int64 juce::AudioFormatReader::searchForLevel	(	int64	startSample,
		int64	numSamplesToSearch,
		double	magnitudeRangeMinimum,
		double	magnitudeRangeMaximum,
		int	minimumConsecutiveSamples
	)

inherited

Scans the source looking for a sample whose magnitude is in a specified range.

This will read from the source, either forwards or backwards between two sample positions, until it finds a sample whose magnitude lies between two specified levels.

If it finds a suitable sample, it returns its position; if not, it will return -1.

There's also a minimumConsecutiveSamples setting to help avoid spikes or zero-crossing points when you're searching for a continuous range of samples

Parameters

startSample	the first sample to look at
numSamplesToSearch	the number of samples to scan. If this value is negative, the search will go backwards
magnitudeRangeMinimum	the lowest magnitude (inclusive) that is considered a hit, from 0 to 1.0
magnitudeRangeMaximum	the highest magnitude (inclusive) that is considered a hit, from 0 to 1.0
minimumConsecutiveSamples	if this is > 0, the method will only look for a sequence of this many consecutive samples, all of which lie within the target range. When it finds such a sequence, it returns the position of the first in-range sample it found (i.e. the earliest one if scanning forwards, the latest one if scanning backwards)

◆ setReadTimeout()

void juce::BufferingAudioReader::setReadTimeout ( int timeoutMilliseconds )

noexcept

Sets a number of milliseconds that the reader can block for in its readSamples() method before giving up and returning silence.

A value of less that 0 means "wait forever". The default timeout is 0.

◆ useTimeSlice()

int juce::BufferingAudioReader::useTimeSlice ( )

overrideprivatevirtual

Called back by a TimeSliceThread.

When you register this class with it, a TimeSliceThread will repeatedly call this method.

The implementation of this method should use its time-slice to do something that's quick - never block for longer than absolutely necessary.

Returns: Your method should return the number of milliseconds which it would like to wait before being called again. Returning 0 will make the thread call again as soon as possible (after possibly servicing other busy clients). If you return a value below zero, your client will be removed from the list of clients, and won't be called again. The value you specify isn't a guarantee, and is only used as a hint by the thread - the actual time before the next callback may be more or less than specified. You can force the TimeSliceThread to wake up and poll again immediately by calling its notify() method.

Implements juce::TimeSliceClient.

Member Data Documentation

◆ bitsPerSample

unsigned int juce::AudioFormatReader::bitsPerSample = 0

inherited

The number of bits per sample, e.g.

16, 24, 32.

◆ blocks

OwnedArray<BufferedBlock> juce::BufferingAudioReader::blocks

private

◆ formatName

String juce::AudioFormatReader::formatName

privateinherited

◆ input

InputStream* juce::AudioFormatReader::input

inherited

The input stream, for use by subclasses.

◆ lengthInSamples

int64 juce::AudioFormatReader::lengthInSamples = 0

inherited

The total number of samples in the audio stream.

◆ lock

CriticalSection juce::BufferingAudioReader::lock

private

◆ metadataValues

StringPairArray juce::AudioFormatReader::metadataValues

inherited

A set of metadata values that the reader has pulled out of the stream.

Exactly what these values are depends on the format, so you can check out the format implementation code to see what kind of stuff they understand.

◆ nextCallTime

Time juce::TimeSliceClient::nextCallTime

privateinherited

◆ nextReadPosition

std::atomic<int64> juce::BufferingAudioReader::nextReadPosition { 0 }

private

◆ numBlocks

const int juce::BufferingAudioReader::numBlocks

private

◆ numChannels

unsigned int juce::AudioFormatReader::numChannels = 0

inherited

The total number of channels in the audio stream.

◆ sampleRate

double juce::AudioFormatReader::sampleRate = 0

inherited

The sample-rate of the stream.

◆ samplesPerBlock

constexpr int juce::BufferingAudioReader::samplesPerBlock = 32768

staticconstexprprivate

◆ source

std::unique_ptr<AudioFormatReader> juce::BufferingAudioReader::source

private

◆ thread

TimeSliceThread& juce::BufferingAudioReader::thread

private

◆ timeoutMs

int juce::BufferingAudioReader::timeoutMs = 0

private

◆ usesFloatingPointData

bool juce::AudioFormatReader::usesFloatingPointData = false

inherited

Indicates whether the data is floating-point or fixed.

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

juce_BufferingAudioFormatReader.h

Classes

Public Member Functions

Public Attributes

Static Protected Member Functions

Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ BufferingAudioReader()

◆ ~BufferingAudioReader()

Member Function Documentation

◆ clearSamplesBeyondAvailableLength()

◆ getBlockContaining()

◆ getChannelLayout()

◆ getFormatName()

◆ read() [1/3]

◆ read() [2/3]

◆ read() [3/3]

◆ readMaxLevels() [1/2]

◆ readMaxLevels() [2/2]

◆ readNextBufferChunk()

◆ readSamples()

◆ searchForLevel()

◆ setReadTimeout()

◆ useTimeSlice()

Member Data Documentation

◆ bitsPerSample

◆ blocks

◆ formatName

◆ input

◆ lengthInSamples

◆ lock

◆ metadataValues

◆ nextCallTime

◆ nextReadPosition

◆ numBlocks

◆ numChannels

◆ sampleRate

◆ samplesPerBlock

◆ source

◆ thread

◆ timeoutMs

◆ usesFloatingPointData