JUCE  v5.4.1-191-g0ab5e696f
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juce::BufferingAudioReader Class Reference

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:

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 StringgetFormatName () const noexcept
 Returns a description of what type of format this is. More...
 
bool read (int *const *destSamples, int numDestChannels, int64 startSampleInSource, int numSamplesToRead, bool fillLeftoverChannelsWithCopies)
 Reads samples from the stream. 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...
 
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...
 
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...
 
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...
 
InputStreaminput
 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 **destSamples, 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 Types

enum  { samplesPerBlock = 32768 }
 

Private Member Functions

BufferedBlockgetBlockContaining (int64 pos) const noexcept
 
bool readNextBufferChunk ()
 
int useTimeSlice () override
 Called back by a TimeSliceThread. More...
 

Private Attributes

OwnedArray< BufferedBlockblocks
 
CriticalSection lock
 
std::atomic< int64nextReadPosition { 0 }
 
const int numBlocks
 
std::unique_ptr< AudioFormatReadersource
 
TimeSliceThreadthread
 
int timeoutMs = 0
 

Detailed Description

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

See also
AudioFormatReader

{Audio}

Member Enumeration Documentation

◆ anonymous enum

anonymous enum
private
Enumerator
samplesPerBlock 

Constructor & Destructor Documentation

◆ BufferingAudioReader()

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

Creates a reader.

Parameters
sourceReaderthe source reader to wrap. This BufferingAudioReader takes ownership of this object and will delete it later when no longer needed
timeSliceThreadthe 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.
samplesToBufferthe total number of samples to buffer ahead.

◆ ~BufferingAudioReader()

juce::BufferingAudioReader::~BufferingAudioReader ( )
override

Member Function Documentation

◆ clearSamplesBeyondAvailableLength()

static void juce::AudioFormatReader::clearSamplesBeyondAvailableLength ( int **  destSamples,
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(), jassert, 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() [1/2]

bool juce::AudioFormatReader::read ( int *const *  destSamples,
int  numDestChannels,
int64  startSampleInSource,
int  numSamplesToRead,
bool  fillLeftoverChannelsWithCopies 
)
inherited

Reads samples from the stream.

Parameters
destSamplesan 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 destSamples[0] is the left channel data, and destSamples[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
numDestChannelsthe number of array elements in the destChannels array
startSampleInSourcethe 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.
numSamplesToReadthe 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
fillLeftoverChannelsWithCopiesif 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

◆ read() [2/2]

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.

◆ readMaxLevels() [1/2]

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
startSamplethe offset into the audio stream to start reading from. It's ok for this to be beyond the start or end of the stream.
numSampleshow many samples to read
resultsthis array will be filled with Range values for each channel. The array must contain numChannels elements.
numChannelsToReadthe 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.

◆ readMaxLevels() [2/2]

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
startSamplethe offset into the audio stream to start reading from. It's ok for this to be beyond the start or end of the stream.
numSampleshow many samples to read
lowestLefton return, this is the lowest absolute sample from the left channel
highestLefton return, this is the highest absolute sample from the left channel
lowestRighton return, this is the lowest absolute sample from the right channel (if there is one)
highestRighton return, this is the highest absolute sample from the right channel (if there is one)
See also
read

◆ readNextBufferChunk()

bool juce::BufferingAudioReader::readNextBufferChunk ( )
private

◆ readSamples()

bool juce::BufferingAudioReader::readSamples ( int **  destSamples,
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
destSamplesthe array of destination buffers to fill. Some of these pointers may be null
numDestChannelsthe number of items in the destSamples array. This value is guaranteed not to be greater than the number of channels that this reader object contains
startOffsetInDestBufferthe number of samples from the start of the dest data at which to begin writing
startSampleInFilethe number of samples into the source data at which to begin reading. This value is guaranteed to be >= 0.
numSamplesthe 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
startSamplethe first sample to look at
numSamplesToSearchthe number of samples to scan. If this value is negative, the search will go backwards
magnitudeRangeMinimumthe lowest magnitude (inclusive) that is considered a hit, from 0 to 1.0
magnitudeRangeMaximumthe highest magnitude (inclusive) that is considered a hit, from 0 to 1.0
minimumConsecutiveSamplesif 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 guaranteee, 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

◆ 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.

◆ 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.

◆ 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: