QAudioFormat Class

The QAudioFormat class stores audio stream parameter information. More...

Header:	#include <QAudioFormat>
qmake:	QT += multimedia

• List of all members, including inherited members

Public Types

enum	Endian { BigEndian, LittleEndian }
enum	SampleType { Unknown, SignedInt, UnSignedInt, Float }

Public Functions

	QAudioFormat()
	QAudioFormat(const QAudioFormat &other)
	~QAudioFormat()
QAudioFormat::Endian	byteOrder() const
qint32	bytesForDuration(qint64 duration) const
qint32	bytesForFrames(qint32 frameCount) const
int	bytesPerFrame() const
int	channelCount() const
QString	codec() const
qint64	durationForBytes(qint32 bytes) const
qint64	durationForFrames(qint32 frameCount) const
qint32	framesForBytes(qint32 byteCount) const
qint32	framesForDuration(qint64 duration) const
bool	isValid() const
int	sampleRate() const
int	sampleSize() const
QAudioFormat::SampleType	sampleType() const
void	setByteOrder(QAudioFormat::Endian byteOrder)
void	setChannelCount(int channels)
void	setCodec(const QString &codec)
void	setSampleRate(int samplerate)
void	setSampleSize(int sampleSize)
void	setSampleType(QAudioFormat::SampleType sampleType)
bool	operator!=(const QAudioFormat &other) const
QAudioFormat &	operator=(const QAudioFormat &other)
bool	operator==(const QAudioFormat &other) const

Detailed Description

The QAudioFormat class stores audio stream parameter information.

An audio format specifies how data in an audio stream is arranged, i.e, how the stream is to be interpreted. The encoding itself is specified by the codec() used for the stream.

In addition to the encoding, QAudioFormat contains other parameters that further specify how the audio sample data is arranged. These are the frequency, the number of channels, the sample size, the sample type, and the byte order. The following table describes these in more detail.

Parameter	Description
Sample Rate	Samples per second of audio data in Hertz.
Number of channels	The number of audio channels (typically one for mono or two for stereo)
Sample size	How much data is stored in each sample (typically 8 or 16 bits)
Sample type	Numerical representation of sample (typically signed integer, unsigned integer or float)
Byte order	Byte ordering of sample (typically little endian, big endian)

This class is typically used in conjunction with QAudioInput or QAudioOutput to allow you to specify the parameters of the audio stream being read or written, or with QAudioBuffer when dealing with samples in memory.

You can obtain audio formats compatible with the audio device used through functions in QAudioDeviceInfo. This class also lets you query available parameter values for a device, so that you can set the parameters yourself. See the QAudioDeviceInfo class description for details. You need to know the format of the audio streams you wish to play or record.

In the common case of interleaved linear PCM data, the codec will be "audio/pcm", and the samples for all channels will be interleaved. One sample for each channel for the same instant in time is referred to as a frame in Qt Multimedia (and other places).

Member Type Documentation

enum QAudioFormat::Endian

Constant	Value	Description
QAudioFormat::BigEndian	QSysInfo::BigEndian	Samples are big endian byte order
QAudioFormat::LittleEndian	QSysInfo::LittleEndian	Samples are little endian byte order

enum QAudioFormat::SampleType

Constant	Value	Description
QAudioFormat::Unknown	0	Not Set
QAudioFormat::SignedInt	1	Samples are signed integers
QAudioFormat::UnSignedInt	2	Samples are unsigned intergers
QAudioFormat::Float	3	Samples are floats

Member Function Documentation

QAudioFormat::QAudioFormat()

Construct a new audio format.

Values are initialized as follows:

• sampleRate() = -1
• channelCount() = -1
• sampleSize() = -1
• byteOrder() = QAudioFormat::Endian(QSysInfo::ByteOrder)
• sampleType() = QAudioFormat::Unknown codec() = ""

QAudioFormat::QAudioFormat(const QAudioFormat &other)

Construct a new audio format using other.

QAudioFormat::~QAudioFormat()

Destroy this audio format.

QAudioFormat::Endian QAudioFormat::byteOrder() const

Returns the current byteOrder value.

See also setByteOrder().

qint32 QAudioFormat::bytesForDuration(qint64 duration) const

Returns the number of bytes required for this audio format for duration microseconds.

Returns 0 if this format is not valid.

Note that some rounding may occur if duration is not an exact fraction of the sampleRate().

See also durationForBytes().

qint32 QAudioFormat::bytesForFrames(qint32 frameCount) const

Returns the number of bytes required for frameCount frames of this format.

Returns 0 if this format is not valid.

See also bytesForDuration().

int QAudioFormat::bytesPerFrame() const

Returns the number of bytes required to represent one frame (a sample in each channel) in this format.

Returns 0 if this format is invalid.

int QAudioFormat::channelCount() const

Returns the current channel count value.

See also setChannelCount().

QString QAudioFormat::codec() const

Returns the current codec identifier.

See also setCodec() and QAudioDeviceInfo::supportedCodecs().

qint64 QAudioFormat::durationForBytes(qint32 bytes) const

Returns the number of microseconds represented by bytes in this format.

Returns 0 if this format is not valid.

Note that some rounding may occur if bytes is not an exact multiple of the number of bytes per frame.

See also bytesForDuration().

qint64 QAudioFormat::durationForFrames(qint32 frameCount) const

Return the number of microseconds represented by frameCount frames in this format.

qint32 QAudioFormat::framesForBytes(qint32 byteCount) const

Returns the number of frames represented by byteCount in this format.

Note that some rounding may occur if byteCount is not an exact multiple of the number of bytes per frame.

Each frame has one sample per channel.

See also framesForDuration().

qint32 QAudioFormat::framesForDuration(qint64 duration) const

Returns the number of frames required to represent duration microseconds in this format.

Note that some rounding may occur if duration is not an exact fraction of the sampleRate().

bool QAudioFormat::isValid() const

Returns true if all of the parameters are valid.

int QAudioFormat::sampleRate() const

Returns the current sample rate in Hertz.

See also setSampleRate().

int QAudioFormat::sampleSize() const

Returns the current sample size value, in bits.

See also setSampleSize() and bytesPerFrame().

QAudioFormat::SampleType QAudioFormat::sampleType() const

Returns the current SampleType value.

See also setSampleType().

void QAudioFormat::setByteOrder(QAudioFormat::Endian byteOrder)

Sets the byteOrder to byteOrder.

See also byteOrder().

void QAudioFormat::setChannelCount(int channels)

Sets the channel count to channels.

See also channelCount().

void QAudioFormat::setCodec(const QString &codec)

Sets the codec to codec.

The parameter to this function should be one of the types reported by the QAudioDeviceInfo::supportedCodecs() function for the audio device you are working with.

See also codec() and QAudioDeviceInfo::supportedCodecs().

void QAudioFormat::setSampleRate(int samplerate)

Sets the sample rate to samplerate Hertz.

See also sampleRate().

void QAudioFormat::setSampleSize(int sampleSize)

Sets the sample size to the sampleSize specified, in bits.

This is typically 8 or 16, but some systems may support higher sample sizes.

See also sampleSize().

void QAudioFormat::setSampleType(QAudioFormat::SampleType sampleType)

Sets the sampleType to sampleType.

See also sampleType().

bool QAudioFormat::operator!=(const QAudioFormat &other) const

Returns true if this QAudioFormat is not equal to the other QAudioFormat; otherwise returns false.

All elements of QAudioFormat are used for the comparison.

QAudioFormat &QAudioFormat::operator=(const QAudioFormat &other)

Assigns other to this QAudioFormat implementation.

bool QAudioFormat::operator==(const QAudioFormat &other) const

Returns true if this QAudioFormat is equal to the other QAudioFormat; otherwise returns false.

All elements of QAudioFormat are used for the comparison.