QMediaRecorder Class

The QMediaRecorder class is used for encoding and recording a capture session. More...

Header:	`#include <QMediaRecorder>`
CMake:	`find_package(Qt6 REQUIRED COMPONENTS Multimedia)` `target_link_libraries(mytarget PRIVATE Qt6::Multimedia)`
qmake:	`QT += multimedia`
In QML:	MediaRecorder
Inherits:	QObject

List of all members, including inherited members

Public Types

enum	EncodingMode { ConstantQualityEncoding, ConstantBitRateEncoding, AverageBitRateEncoding, TwoPassEncoding }
enum	Error { NoError, ResourceError, FormatError, OutOfSpaceError, LocationNotWritable }
enum	Quality { VeryLowQuality, LowQuality, NormalQuality, HighQuality, VeryHighQuality }
enum	RecorderState { StoppedState, RecordingState, PausedState }

Properties

actualLocation : const QUrl
autoStop : bool
duration : const qint64
error : const QMediaRecorder::Error
errorString : const QString

mediaFormat : QMediaFormat
metaData : QMediaMetaData
outputLocation : QUrl
quality : Quality
recorderState : const QMediaRecorder::RecorderState

Public Functions

	QMediaRecorder(QObject *parent = nullptr)
virtual	~QMediaRecorder()
QUrl	actualLocation() const
void	addMetaData(const QMediaMetaData &metaData)
int	audioBitRate() const
int	audioChannelCount() const
int	audioSampleRate() const
bool	autoStop() const
QMediaCaptureSession *	captureSession() const
qint64	duration() const
QMediaRecorder::EncodingMode	encodingMode() const
QMediaRecorder::Error	error() const
QString	errorString() const
bool	isAvailable() const
QMediaFormat	mediaFormat() const
QMediaMetaData	metaData() const
QIODevice *	outputDevice() const
QUrl	outputLocation() const
QMediaRecorder::Quality	quality() const
QMediaRecorder::RecorderState	recorderState() const
void	setAudioBitRate(int bitRate)
void	setAudioChannelCount(int channels)
void	setAudioSampleRate(int sampleRate)
void	setAutoStop(bool autoStop)
void	setEncodingMode(QMediaRecorder::EncodingMode mode)
void	setMediaFormat(const QMediaFormat &format)
void	setMetaData(const QMediaMetaData &metaData)
void	setOutputDevice(QIODevice *device)
void	setOutputLocation(const QUrl &location)
void	setQuality(QMediaRecorder::Quality quality)
void	setVideoBitRate(int bitRate)
void	setVideoFrameRate(qreal frameRate)
void	setVideoResolution(const QSize &size)
void	setVideoResolution(int width, int height)
int	videoBitRate() const
qreal	videoFrameRate() const
QSize	videoResolution() const

Public Slots

void	pause()
void	record()
void	stop()

Signals

void	actualLocationChanged(const QUrl &location)
void	audioBitRateChanged()
void	audioChannelCountChanged()
void	audioSampleRateChanged()
void	autoStopChanged()
void	durationChanged(qint64 duration)
void	encoderSettingsChanged()
void	encodingModeChanged()
void	errorChanged()
void	errorOccurred(QMediaRecorder::Error error, const QString &errorString)
void	mediaFormatChanged()
void	metaDataChanged()
void	qualityChanged()
void	recorderStateChanged(QMediaRecorder::RecorderState state)
void	videoBitRateChanged()
void	videoFrameRateChanged()
void	videoResolutionChanged()

Detailed Description

Use the QMediaRecorder class to encode and record media generated in QMediaCaptureSession. You can generate:

Audio. Use QAudioInput or QAudioBufferInput.
Video. Use QCamera, QScreenCapture, QWindowCapture, or QVideoFrameInput.

To record media, connect a generator to a corresponding media capture session.

Performance of video encoding and recording is limited by the hardware, the operating system, the installed graphic drivers, and the input video format. If QCamera, QScreenCapture, or QWindowCapture produces video frames faster than QMediaRecorder can encode and record them, the recorder may drop some frames. This is likely to occur if the input frame resolution is high, 4K for example, and hardware-accelerated encoding is unavailable. If you generate input video via QVideoFrameInput, the method QVideoFrameInput::sendVideoFrame will do nothing and return false whenever this limitation is reached and the internal frame queue is full. Rely on the signal QVideoFrameInput::readyToSendVideoFrame to know when the recorder is ready to receive new frames again. If you cannot change the rate of video frame generation and dropping frames is undesirable, we recommend implementing your own frame queue on top of QVideoFrameInput, considering the memory limitations of the hardware.

 QMediaCaptureSession session;
 QAudioInput audioInput;
 session.setAudioInput(&input);
 QMediaRecorder recorder;
 session.setRecorder(&recorder);
 recorder.setQuality(QMediaRecorder::HighQuality);
 recorder.setOutputLocation(QUrl::fromLocalFile("test.mp3"));
 recorder.record();

Member Type Documentation

enum QMediaRecorder::EncodingMode

Enumerates encoding modes.

Constant	Value	Description
`QMediaRecorder::ConstantQualityEncoding`	`0`	Encoding will aim to have a constant quality, adjusting bitrate to fit.
`QMediaRecorder::ConstantBitRateEncoding`	`1`	Encoding will use a constant bit rate, adjust quality to fit.
`QMediaRecorder::AverageBitRateEncoding`	`2`	Encoding will try to keep an average bitrate setting, but will use more or less as needed.
`QMediaRecorder::TwoPassEncoding`	`3`	The media will first be processed to determine the characteristics, and then processed a second time allocating more bits to the areas that need it.

enum QMediaRecorder::Error

Constant	Value	Description
`QMediaRecorder::NoError`	`0`	No Errors.
`QMediaRecorder::ResourceError`	`1`	Device is not ready or not available.
`QMediaRecorder::FormatError`	`2`	Current format is not supported.
`QMediaRecorder::OutOfSpaceError`	`3`	No space left on device.
`QMediaRecorder::LocationNotWritable`	`4`	The output location is not writable.

enum QMediaRecorder::Quality

Enumerates quality encoding levels.

Constant	Value
`QMediaRecorder::VeryLowQuality`	`0`
`QMediaRecorder::LowQuality`	`1`
`QMediaRecorder::NormalQuality`	`2`
`QMediaRecorder::HighQuality`	`3`
`QMediaRecorder::VeryHighQuality`	`4`

enum QMediaRecorder::RecorderState

Constant	Value	Description
`QMediaRecorder::StoppedState`	`0`	The recorder is not active.
`QMediaRecorder::RecordingState`	`1`	The recording is requested.
`QMediaRecorder::PausedState`	`2`	The recorder is paused.

Property Documentation

`[read-only]` actualLocation : const QUrl

This property holds the actual location of the last media content.

The actual location is usually available after recording starts, and reset when new location is set or new recording starts.

Access functions:

QUrl	actualLocation() const

Notifier signal:

void	actualLocationChanged(const QUrl &location)

autoStop : bool

This property controls whether the media recorder stops automatically when all media inputs have reported the end of the stream or have been deactivated.

The end of the stream is reported by sending an empty media frame, which you can send explicitly via QVideoFrameInput or QAudioBufferInput.

Video inputs, specificly, QCamera, QScreenCapture and QWindowCapture, can be deactivated via the function setActive.

Defaults to false.

Access functions:

bool	autoStop() const
void	setAutoStop(bool autoStop)

Notifier signal:

void	autoStopChanged()

See also QCamera, QScreenCapture, and QWindowCapture.

`[read-only]` duration : const qint64

This property holds the recorded media duration in milliseconds.

Access functions:

qint64 duration() const

Notifier signal:

void	durationChanged(qint64 duration)

`[read-only]` error : const QMediaRecorder::Error

Returns the current error state.

Access functions:

QMediaRecorder::Error error() const

Notifier signal:

void	errorChanged()

See also errorString().

`[read-only]` errorString : const QString

Returns a string describing the current error state.

Access functions:

QString errorString() const

Notifier signal:

void	errorChanged()

See also error().

mediaFormat : QMediaFormat

Returns the recording media format.

Access functions:

QMediaFormat	mediaFormat() const
void	setMediaFormat(const QMediaFormat &format)

Notifier signal:

void	mediaFormatChanged()

metaData : QMediaMetaData

Returns the metaData associated with the recording.

Access functions:

QMediaMetaData	metaData() const
void	setMetaData(const QMediaMetaData &metaData)

Notifier signal:

void	metaDataChanged()

outputLocation : QUrl

This property holds the destination location of media content.

Setting the location can fail, for example when the service supports only local file system locations but a network URL was passed. If the operation fails an errorOccured() signal is emitted.

The output location can be relative or empty; in the latter case the recorder uses the system specific place and file naming scheme.

Access functions:

QUrl	outputLocation() const
void	setOutputLocation(const QUrl &location)

quality : Quality

Returns the recording quality.

Access functions:

QMediaRecorder::Quality	quality() const
void	setQuality(QMediaRecorder::Quality quality)

Notifier signal:

void	qualityChanged()

`[read-only]` recorderState : const QMediaRecorder::RecorderState

This property holds the current state of the media recorder.

The state property represents the user request and is changed synchronously during record(), pause() or stop() calls. Recorder state may also change asynchronously when recording fails.

Access functions:

QMediaRecorder::RecorderState recorderState() const

Notifier signal:

void	recorderStateChanged(QMediaRecorder::RecorderState state)

Member Function Documentation

QMediaRecorder::QMediaRecorder(QObject **parent* = nullptr)

Constructs a media recorder. The media recorder is a child of parent.

`[virtual noexcept]` QMediaRecorder::~QMediaRecorder()

Destroys a media recorder object.

`[signal]` void QMediaRecorder::actualLocationChanged(const QUrl &location)

Signals that the actual location of the recorded media has changed. This signal is usually emitted when recording starts.

Note: Notifier signal for property actualLocation.

void QMediaRecorder::addMetaData(const QMediaMetaData &metaData)

Adds metaData to the recorded media.

int QMediaRecorder::audioBitRate() const

Returns the bit rate of the compressed audio stream in bits per second.

Note: Getter function for property audioBitRate.

See also setAudioBitRate().

`[signal]` void QMediaRecorder::audioBitRateChanged()

Signals when the recording audio bit rate changes.

Note: Notifier signal for property audioBitRate.

int QMediaRecorder::audioChannelCount() const

Returns the number of audio channels.

Note: Getter function for property audioChannelCount.

See also setAudioChannelCount().

`[signal]` void QMediaRecorder::audioChannelCountChanged()

Signals when the recording audio channel count changes.

Note: Notifier signal for property audioChannelCount.

int QMediaRecorder::audioSampleRate() const

Returns the audio sample rate in Hz.

Note: Getter function for property audioSampleRate.

See also setAudioSampleRate().

`[signal]` void QMediaRecorder::audioSampleRateChanged()

Signals when the recording audio sample rate changes.

Note: Notifier signal for property audioSampleRate.

QMediaCaptureSession *QMediaRecorder::captureSession() const

Returns the media capture session.

`[signal]` void QMediaRecorder::durationChanged(qint64 duration)

Signals that the duration of the recorded media has changed.

Note: Notifier signal for property duration.

`[signal]` void QMediaRecorder::encoderSettingsChanged()

Signals when the encoder settings change.

QMediaRecorder::EncodingMode QMediaRecorder::encodingMode() const

Returns the encoding mode.

Note: Getter function for property encodingMode.

See also setEncodingMode() and EncodingMode.

`[signal]` void QMediaRecorder::encodingModeChanged()

Signals when the encoding mode changes.

Note: Notifier signal for property encodingMode.

`[signal]` void QMediaRecorder::errorOccurred(QMediaRecorder::Error error, const QString &errorString)

Signals that an error has occurred, with errorString containing a description of the error.

bool QMediaRecorder::isAvailable() const

Returns true if media recorder service ready to use.

`[signal]` void QMediaRecorder::metaDataChanged()

Signals that a media object's meta-data has changed.

If multiple meta-data elements are changed metaDataChanged() is emitted once.

Note: Notifier signal for property metaData.

QIODevice *QMediaRecorder::outputDevice() const

Returns the output IO device for media content.

See also setOutputDevice().

`[slot]` void QMediaRecorder::pause()

Pauses recording.

The recorder state is changed to QMediaRecorder::PausedState.

Depending on the platform, pausing recording may be not supported. In this case the recorder state is unchanged.

`[signal]` void QMediaRecorder::qualityChanged()

Signals when the recording quality changes.

Note: Notifier signal for property quality.

`[slot]` void QMediaRecorder::record()

Start recording.

While the recorder state is changed immediately to c{QMediaRecorder::RecordingState}, recording may start asynchronously.

If recording fails error() signal is emitted with recorder state being reset back to QMediaRecorder::StoppedState.

Note: On mobile devices, recording will happen in the orientation the device had when calling record and is locked for the duration of the recording. To avoid artifacts on the user interface, we recommend to keep the user interface locked to the same orientation as long as the recording is ongoing using the contentOrientation property of QWindow and unlock it again once the recording is finished.

QMediaRecorder::RecorderState QMediaRecorder::recorderState() const

Returns the current media recorder state.

Note: Getter function for property recorderState.

See also QMediaRecorder::RecorderState.

`[signal]` void QMediaRecorder::recorderStateChanged(QMediaRecorder::RecorderState state)

Signals that a media recorder's state has changed.

Note: Notifier signal for property recorderState.

void QMediaRecorder::setAudioBitRate(int bitRate)

Sets the audio bitRate in bits per second.

Note: Setter function for property audioBitRate.

See also audioBitRate().

void QMediaRecorder::setAudioChannelCount(int channels)

Sets the number of audio channels.

A value of -1 indicates the recorder should make an optimal choice based on what is available from the audio source and the limitations of the codec.

Note: Setter function for property audioChannelCount.

See also audioChannelCount().

void QMediaRecorder::setAudioSampleRate(int sampleRate)

Sets the audio sampleRate in Hz.

A value of -1 indicates the recorder should make an optimal choice based on what is available from the audio source, and the limitations of the codec.

Note: Setter function for property audioSampleRate.

See also audioSampleRate().

void QMediaRecorder::setEncodingMode(QMediaRecorder::EncodingMode mode)

Sets the encoding mode setting.

If ConstantQualityEncoding is set, the quality encoding parameter is used and bit rates are ignored, otherwise the bitrates are used.

Note: Setter function for property encodingMode.

See also encodingMode() and EncodingMode.

void QMediaRecorder::setMetaData(const QMediaMetaData &metaData)

Sets the meta data to metaData.

Note: To ensure that meta-data is set correctly, it should be set before starting the recording. Once the recording is started, any meta-data set will be attached to the next recording.

Note: Setter function for property metaData.

See also metaData().

void QMediaRecorder::setOutputDevice(QIODevice **device*)

Set the output IO device for media content.

The device must have been opened in the WriteOnly or ReadWrite modes before the recording starts.

The media recorder doesn't take ownership of the specified device. If the recording has been started, the device must be kept alive and open until the signal recorderStateChanged(StoppedState) is emitted.

See also outputDevice().

void QMediaRecorder::setVideoBitRate(int bitRate)

Sets the video bitRate in bits per second.

Note: Setter function for property videoBitRate.

See also videoBitRate().

void QMediaRecorder::setVideoFrameRate(qreal frameRate)

Sets the video frameRate.

A value of 0 indicates the recorder should make an optimal choice based on what is available from the video source and the limitations of the codec.

Note: Setter function for property videoFrameRate.

See also videoFrameRate().

void QMediaRecorder::setVideoResolution(const QSize &size)

Sets the resolution of the encoded video to size.

Pass an empty QSize to make the recorder choose an optimal resolution based on what is available from the video source and the limitations of the codec.

Note: Setter function for property videoResolution.

See also videoResolution().

void QMediaRecorder::setVideoResolution(int width, int height)

Sets the width and height of the resolution of the encoded video.

This is an overloaded function.

Note: Setter function for property videoResolution.

`[slot]` void QMediaRecorder::stop()

The recorder will stop the recording. Processing pending video and audio data might however still take some time. The recording is finished, once the state of the media recorder changes to QMediaRecorder::StoppedState.

int QMediaRecorder::videoBitRate() const

Returns the bit rate of the compressed video stream in bits per second.

Note: Getter function for property videoBitRate.

See also setVideoBitRate().

`[signal]` void QMediaRecorder::videoBitRateChanged()

Signals when the recording video bit rate changes.

Note: Notifier signal for property videoBitRate.

qreal QMediaRecorder::videoFrameRate() const

Returns the video frame rate.

Note: Getter function for property videoFrameRate.

See also setVideoFrameRate().

`[signal]` void QMediaRecorder::videoFrameRateChanged()

Signals when the recording video frame rate changes.

Note: Notifier signal for property videoFrameRate.

QSize QMediaRecorder::videoResolution() const

Returns the resolution of the encoded video.

Note: Getter function for property videoResolution.

See also setVideoResolution().

`[signal]` void QMediaRecorder::videoResolutionChanged()

Signals when the video recording resolution changes.

Note: Notifier signal for property videoResolution.

Contents

QMediaRecorder Class

Public Types

Properties

Public Functions

Public Slots

Signals

Detailed Description

Member Type Documentation

enum QMediaRecorder::EncodingMode

enum QMediaRecorder::Error

enum QMediaRecorder::Quality

enum QMediaRecorder::RecorderState

Property Documentation

[read-only] actualLocation : const QUrl

autoStop : bool

[read-only] duration : const qint64

[read-only] error : const QMediaRecorder::Error

[read-only] errorString : const QString

mediaFormat : QMediaFormat

metaData : QMediaMetaData

outputLocation : QUrl

quality : Quality

[read-only] recorderState : const QMediaRecorder::RecorderState

Member Function Documentation

QMediaRecorder::QMediaRecorder(QObject *parent = nullptr)

[virtual noexcept] QMediaRecorder::~QMediaRecorder()

[signal] void QMediaRecorder::actualLocationChanged(const QUrl &location)

void QMediaRecorder::addMetaData(const QMediaMetaData &metaData)

int QMediaRecorder::audioBitRate() const

[signal] void QMediaRecorder::audioBitRateChanged()

int QMediaRecorder::audioChannelCount() const

[signal] void QMediaRecorder::audioChannelCountChanged()

int QMediaRecorder::audioSampleRate() const

[signal] void QMediaRecorder::audioSampleRateChanged()

QMediaCaptureSession *QMediaRecorder::captureSession() const

[signal] void QMediaRecorder::durationChanged(qint64 duration)

[signal] void QMediaRecorder::encoderSettingsChanged()

QMediaRecorder::EncodingMode QMediaRecorder::encodingMode() const

[signal] void QMediaRecorder::encodingModeChanged()

[signal] void QMediaRecorder::errorOccurred(QMediaRecorder::Error error, const QString &errorString)

bool QMediaRecorder::isAvailable() const

[signal] void QMediaRecorder::metaDataChanged()

QIODevice *QMediaRecorder::outputDevice() const

[slot] void QMediaRecorder::pause()

[signal] void QMediaRecorder::qualityChanged()

[slot] void QMediaRecorder::record()

QMediaRecorder::RecorderState QMediaRecorder::recorderState() const

[signal] void QMediaRecorder::recorderStateChanged(QMediaRecorder::RecorderState state)

void QMediaRecorder::setAudioBitRate(int bitRate)

void QMediaRecorder::setAudioChannelCount(int channels)

void QMediaRecorder::setAudioSampleRate(int sampleRate)

void QMediaRecorder::setEncodingMode(QMediaRecorder::EncodingMode mode)

void QMediaRecorder::setMetaData(const QMediaMetaData &metaData)

void QMediaRecorder::setOutputDevice(QIODevice *device)

void QMediaRecorder::setVideoBitRate(int bitRate)

void QMediaRecorder::setVideoFrameRate(qreal frameRate)

void QMediaRecorder::setVideoResolution(const QSize &size)

void QMediaRecorder::setVideoResolution(int width, int height)

[slot] void QMediaRecorder::stop()

int QMediaRecorder::videoBitRate() const

[signal] void QMediaRecorder::videoBitRateChanged()

qreal QMediaRecorder::videoFrameRate() const

[signal] void QMediaRecorder::videoFrameRateChanged()

QSize QMediaRecorder::videoResolution() const

[signal] void QMediaRecorder::videoResolutionChanged()

`[read-only]` actualLocation : const QUrl

`[read-only]` duration : const qint64

`[read-only]` error : const QMediaRecorder::Error

`[read-only]` errorString : const QString

`[read-only]` recorderState : const QMediaRecorder::RecorderState

QMediaRecorder::QMediaRecorder(QObject **parent* = nullptr)

`[virtual noexcept]` QMediaRecorder::~QMediaRecorder()

`[signal]` void QMediaRecorder::actualLocationChanged(const QUrl &location)

`[signal]` void QMediaRecorder::audioBitRateChanged()

`[signal]` void QMediaRecorder::audioChannelCountChanged()

`[signal]` void QMediaRecorder::audioSampleRateChanged()

`[signal]` void QMediaRecorder::durationChanged(qint64 duration)

`[signal]` void QMediaRecorder::encoderSettingsChanged()

`[signal]` void QMediaRecorder::encodingModeChanged()

`[signal]` void QMediaRecorder::errorOccurred(QMediaRecorder::Error error, const QString &errorString)

`[signal]` void QMediaRecorder::metaDataChanged()

`[slot]` void QMediaRecorder::pause()

`[signal]` void QMediaRecorder::qualityChanged()

`[slot]` void QMediaRecorder::record()

`[signal]` void QMediaRecorder::recorderStateChanged(QMediaRecorder::RecorderState state)

void QMediaRecorder::setOutputDevice(QIODevice **device*)

`[slot]` void QMediaRecorder::stop()

`[signal]` void QMediaRecorder::videoBitRateChanged()

`[signal]` void QMediaRecorder::videoFrameRateChanged()

`[signal]` void QMediaRecorder::videoResolutionChanged()