A specialised type of AudioFormatReader that uses a MemoryMappedFile to read directly from an audio file. More...

#include <juce_MemoryMappedAudioFormatReader.h>

Inheritance diagram for juce::MemoryMappedAudioFormatReader:

Collaboration diagram for juce::MemoryMappedAudioFormatReader:

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Public Member Functions
virtual AudioChannelSet	getChannelLayout ()
	Get the channel layout of the audio stream.

const File &	getFile () const noexcept
	Returns the file that is being mapped.

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

Range< int64 >	getMappedSection () const noexcept
	Returns the sample range that's currently memory-mapped and available for reading.

size_t	getNumBytesUsed () const
	Returns the number of bytes currently being mapped.

virtual void	getSample (int64 sampleIndex, float *result) const noexcept=0
	Returns the samples for all channels at a given sample position.

bool	mapEntireFile ()
	Attempts to map the entire file into memory.

virtual bool	mapSectionOfFile (Range< int64 > samplesToMap)
	Attempts to map a section of the file into memory.

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

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

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

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.

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.

virtual bool	readSamples (int const destChannels, int numDestChannels, int startOffsetInDestBuffer, int64 startSampleInFile, int numSamples)=0
	Subclasses must implement this method to perform the low-level read operation.

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.

void	touchSample (int64 sample) const noexcept
	Touches the memory for the given sample, to force it to be loaded into active memory.

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

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

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

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

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

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

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

Protected Member Functions
	MemoryMappedAudioFormatReader (const File &file, const AudioFormatReader &details, int64 dataChunkStart, int64 dataChunkLength, int bytesPerFrame)
	Creates an MemoryMappedAudioFormatReader object.

int64	filePosToSample (int64 filePos) const noexcept
	Converts a byte position in the file to a sample index.

int64	sampleToFilePos (int64 sample) const noexcept
	Converts a sample index to a byte position in the file.

const void *	sampleToPointer (int64 sample) const noexcept
	Converts a sample index to a pointer to the mapped file memory.

template<typename SampleType , typename Endianness >
Range< float >	scanMinAndMaxInterleaved (int channel, int64 startSampleInFile, int64 numSamples) const noexcept
	Used by AudioFormatReader subclasses to scan for min/max ranges in interleaved data.

Static Protected Member Functions
static void	clearSamplesBeyondAvailableLength (int const 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.

Protected Attributes
int	bytesPerFrame

int64	dataChunkStart

int64	dataLength

File	file

std::unique_ptr< MemoryMappedFile >	map

Range< int64 >	mappedSection

Private Attributes
String	formatName

Detailed Description

A specialised type of AudioFormatReader that uses a MemoryMappedFile to read directly from an audio file.

This allows for incredibly fast random-access to sample data in the mapped region of the file, but not all audio formats support it - see AudioFormat::createMemoryMappedReader().

Note that before reading samples from a MemoryMappedAudioFormatReader, you must first call mapEntireFile() or mapSectionOfFile() to ensure that the region you want to read has been mapped.

See also: AudioFormat::createMemoryMappedReader, AudioFormatReader

@tags{Audio}

Constructor & Destructor Documentation

◆ MemoryMappedAudioFormatReader()

juce::MemoryMappedAudioFormatReader::MemoryMappedAudioFormatReader	(	const File &	file,
		const AudioFormatReader &	details,
		int64	dataChunkStart,
		int64	dataChunkLength,
		int	bytesPerFrame
	)

protected

Creates an MemoryMappedAudioFormatReader object.

Note that before attempting to read any data, you must call mapEntireFile() or mapSectionOfFile() to ensure that the region you want to read has been mapped.

Member Function Documentation

◆ clearSamplesBeyondAvailableLength()

static void juce::AudioFormatReader::clearSamplesBeyondAvailableLength	(	int const	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 jassertfalse, and juce::zeromem().

◆ filePosToSample()

int64 juce::MemoryMappedAudioFormatReader::filePosToSample ( int64 filePos ) const

inlineprotectednoexcept

Converts a byte position in the file to a sample index.

◆ getChannelLayout()

virtual AudioChannelSet juce::AudioFormatReader::getChannelLayout ( )

virtualinherited

Get the channel layout of the audio stream.

◆ getFile()

const File & juce::MemoryMappedAudioFormatReader::getFile ( ) const

inlinenoexcept

Returns the file that is being mapped.

◆ getFormatName()

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

inlinenoexceptinherited

Returns a description of what type of format this is.

E.g. "AIFF"

◆ getMappedSection()

Range< int64 > juce::MemoryMappedAudioFormatReader::getMappedSection ( ) const

inlinenoexcept

Returns the sample range that's currently memory-mapped and available for reading.

◆ getNumBytesUsed()

size_t juce::MemoryMappedAudioFormatReader::getNumBytesUsed ( ) const

inline

Returns the number of bytes currently being mapped.

◆ getSample()

virtual void juce::MemoryMappedAudioFormatReader::getSample	(	int64	sampleIndex,
		float *	result
	)		const

pure virtualnoexcept

Returns the samples for all channels at a given sample position.

The result array must be large enough to hold a value for each channel that this reader contains.

◆ mapEntireFile()

bool juce::MemoryMappedAudioFormatReader::mapEntireFile ( )

Attempts to map the entire file into memory.

◆ mapSectionOfFile()

virtual bool juce::MemoryMappedAudioFormatReader::mapSectionOfFile ( Range< int64 > samplesToMap )

virtual

Attempts to map a section of the file into memory.

◆ read() [1/3]

bool 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.

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

◆ 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

Reimplemented in juce::AudioSubsectionReader.

◆ 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, and juce::AudioSubsectionReader.

◆ readSamples()

virtual bool juce::AudioFormatReader::readSamples	(	int const	destChannels,
		int	numDestChannels,
		int	startOffsetInDestBuffer,
		int64	startSampleInFile,
		int	numSamples
	)

pure virtualinherited

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

Implemented in juce::ARAAudioSourceReader, juce::ARAPlaybackRegionReader, juce::AudioSubsectionReader, juce::BufferingAudioReader, and juce::AudioCDReader.

◆ sampleToFilePos()

int64 juce::MemoryMappedAudioFormatReader::sampleToFilePos ( int64 sample ) const

inlineprotectednoexcept

Converts a sample index to a byte position in the file.

◆ sampleToPointer()

const void * juce::MemoryMappedAudioFormatReader::sampleToPointer ( int64 sample ) const

inlineprotectednoexcept

Converts a sample index to a pointer to the mapped file memory.

References juce::addBytesToPointer().

◆ scanMinAndMaxInterleaved()

template<typename SampleType , typename Endianness >

Range< float > juce::MemoryMappedAudioFormatReader::scanMinAndMaxInterleaved	(	int	channel,
		int64	startSampleInFile,
		int64	numSamples
	)		const

inlineprotectednoexcept

Used by AudioFormatReader subclasses to scan for min/max ranges in interleaved data.

References juce::addBytesToPointer(), and juce::Range< ValueType >::findMinAndMax().

◆ 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)

◆ touchSample()

void juce::MemoryMappedAudioFormatReader::touchSample ( int64 sample ) const

noexcept

Touches the memory for the given sample, to force it to be loaded into active memory.

Member Data Documentation

◆ bitsPerSample

unsigned int juce::AudioFormatReader::bitsPerSample = 0

inherited

The number of bits per sample, e.g.

16, 24, 32.

◆ bytesPerFrame

int juce::MemoryMappedAudioFormatReader::bytesPerFrame

protected

◆ dataChunkStart

int64 juce::MemoryMappedAudioFormatReader::dataChunkStart

protected

◆ dataLength

int64 juce::MemoryMappedAudioFormatReader::dataLength

protected

◆ file

File juce::MemoryMappedAudioFormatReader::file

protected

◆ 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.

◆ map

std::unique_ptr<MemoryMappedFile> juce::MemoryMappedAudioFormatReader::map

protected

◆ mappedSection

Range<int64> juce::MemoryMappedAudioFormatReader::mappedSection

protected

◆ 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.

◆ 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.

◆ 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_MemoryMappedAudioFormatReader.h

Public Member Functions

Public Attributes

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ MemoryMappedAudioFormatReader()

Member Function Documentation

◆ clearSamplesBeyondAvailableLength()

◆ filePosToSample()

◆ getChannelLayout()

◆ getFile()

◆ getFormatName()

◆ getMappedSection()

◆ getNumBytesUsed()

◆ getSample()

◆ mapEntireFile()

◆ mapSectionOfFile()

◆ read() [1/3]

◆ read() [2/3]

◆ read() [3/3]

◆ readMaxLevels() [1/2]

◆ readMaxLevels() [2/2]

◆ readSamples()

◆ sampleToFilePos()

◆ sampleToPointer()

◆ scanMinAndMaxInterleaved()

◆ searchForLevel()

◆ touchSample()

Member Data Documentation

◆ bitsPerSample

◆ bytesPerFrame

◆ dataChunkStart

◆ dataLength

◆ file

◆ formatName

◆ input

◆ lengthInSamples

◆ map

◆ mappedSection

◆ metadataValues

◆ numChannels

◆ sampleRate

◆ usesFloatingPointData