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

Inherited by AudioCDReader, and AudioSubsectionReader.

Classes
struct	ReadHelper
	Used by AudioFormatReader subclasses to copy data to different formats. More...
Public Member Functions
virtual	~AudioFormatReader ()
	Destructor.
const String &	getFormatName () const noexcept
	Returns a description of what type of format this is.
bool	read (int const destSamples, 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.
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.
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.
Public Attributes
double	sampleRate
	The sample-rate of the stream.
unsigned int	bitsPerSample
	The number of bits per sample, e.g.
int64	lengthInSamples
	The total number of samples in the audio stream.
unsigned int	numChannels
	The total number of channels in the audio stream.
bool	usesFloatingPointData
	Indicates whether the data is floating-point or fixed.
StringPairArray	metadataValues
	A set of metadata values that the reader has pulled out of the stream.
InputStream *	input
	The input stream, for use by subclasses.
Protected Member Functions
	AudioFormatReader (InputStream *sourceStream, const String &formatName)
	Creates an AudioFormatReader object.

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	(	InputStream *	sourceStream,
		const String &	formatName
	)		`[protected]`

Creates an AudioFormatReader object.

Parameters:

sourceStream	the 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 0).
formatName	the description that will be returned by the getFormatName() method

virtual AudioFormatReader::~AudioFormatReader ( ) [virtual]

Destructor.

Member Function Documentation

const String& AudioFormatReader::getFormatName ( ) const

Returns a description of what type of format this is.

E.g. "AIFF"

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

Reads samples from the stream.

Parameters:

destSamples	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 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
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

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:

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 AudioSubsectionReader.

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:

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)

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:

destSamples	the array of destination buffers to fill. Some of these pointers may be null
numDestChannels	the 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
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