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AudioFormatReader Class Referenceabstract

Reads samples from an audio file stream. More...

Inheritance diagram for AudioFormatReader:

Classes

struct  ReadHelper
 Used by AudioFormatReader subclasses to copy data to different formats. More...
 

Public Member Functions

virtual ~AudioFormatReader ()
 Destructor. 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...
 
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...
 
virtual AudioChannelSet getChannelLayout ()
 Get the channel layout of the audio stream. More...
 
virtual bool readSamples (int **destSamples, int numDestChannels, int startOffsetInDestBuffer, int64 startSampleInFile, int numSamples)=0
 Subclasses must implement this method to perform the low-level read operation. More...
 

Public Attributes

double sampleRate = 0
 The sample-rate of the stream. More...
 
unsigned int bitsPerSample = 0
 The number of bits per sample, e.g. More...
 
int64 lengthInSamples = 0
 The total number of samples in the audio stream. More...
 
unsigned int numChannels = 0
 The total number of channels in the audio stream. More...
 
bool usesFloatingPointData = false
 Indicates whether the data is floating-point or fixed. More...
 
StringPairArray metadataValues
 A set of metadata values that the reader has pulled out of the stream. More...
 
InputStreaminput
 The input stream, for use by subclasses. More...
 

Protected Member Functions

 AudioFormatReader (InputStream *sourceStream, const String &formatName)
 Creates an AudioFormatReader object. 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...
 

Detailed Description

Reads samples from an audio file stream.

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

See also
AudioFormat, AudioFormatWriter

Constructor & Destructor Documentation

◆ AudioFormatReader()

AudioFormatReader::AudioFormatReader ( InputStream sourceStream,
const String formatName 
)
protected

Creates an AudioFormatReader object.

Parameters
sourceStreamthe stream to read from - this will be deleted by this object when it is no longer needed. (Some specialised readers might not use this parameter and can leave it as nullptr).
formatNamethe description that will be returned by the getFormatName() method

◆ ~AudioFormatReader()

virtual AudioFormatReader::~AudioFormatReader ( )
virtual

Destructor.

Member Function Documentation

◆ getFormatName()

const String& AudioFormatReader::getFormatName ( ) const
noexcept

Returns a description of what type of format this is.

E.g. "AIFF"

◆ read() [1/2]

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

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

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

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 AudioSubsectionReader.

◆ readMaxLevels() [2/2]

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

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

◆ searchForLevel()

int64 AudioFormatReader::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.

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)

◆ getChannelLayout()

virtual AudioChannelSet AudioFormatReader::getChannelLayout ( )
virtual

Get the channel layout of the audio stream.

◆ readSamples()

virtual bool AudioFormatReader::readSamples ( int **  destSamples,
int  numDestChannels,
int  startOffsetInDestBuffer,
int64  startSampleInFile,
int  numSamples 
)
pure virtual

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

Implemented in AudioCDReader, AudioSubsectionReader, and BufferingAudioReader.

◆ clearSamplesBeyondAvailableLength()

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

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

References jassert, and zeromem().

Member Data Documentation

◆ sampleRate

double AudioFormatReader::sampleRate = 0

The sample-rate of the stream.

◆ bitsPerSample

unsigned int AudioFormatReader::bitsPerSample = 0

The number of bits per sample, e.g.

16, 24, 32.

◆ lengthInSamples

int64 AudioFormatReader::lengthInSamples = 0

The total number of samples in the audio stream.

◆ numChannels

unsigned int AudioFormatReader::numChannels = 0

The total number of channels in the audio stream.

◆ usesFloatingPointData

bool AudioFormatReader::usesFloatingPointData = false

Indicates whether the data is floating-point or fixed.

◆ metadataValues

StringPairArray AudioFormatReader::metadataValues

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.

◆ input

InputStream* AudioFormatReader::input

The input stream, for use by subclasses.


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