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MediaRecorder QML Type

For encoding and recording media generated in a CaptureSession. More...

Import Statement: import QtMultimedia
In C++: QMediaRecorder

Properties

Signals

Methods

Detailed Description

Use the MediaRecorder element within a CaptureSession to encode and record:

  • Audio captured from an audio interface (like microphone or line input).
  • Video captured from camera, screen, or an application window.

Performance of video encoding and recording is limited by the hardware, the operating system, the installed graphic drivers, and the input video format. If Camera, ScreenCapture, or WindowCapture produces video frames faster than MediaRecorder 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.

The code below shows a simple capture session containing a MediaRecorder using the default camera and default audio input.

CaptureSession {
    id: captureSession
    camera: Camera {
        id: camera
        active: true
    }
    audioInput: AudioInput {}
    recorder: MediaRecorder {
        id: recorder
    }
}

The code below shows how the recording can be started and stopped.

CameraButton {
    text: "Record"
    visible: recorder.recorderState !== MediaRecorder.RecordingState
    onClicked: recorder.record()
}

CameraButton {
    id: stopButton
    text: "Stop"
    visible: recorder.recorderState === MediaRecorder.RecordingState
    onClicked: recorder.stop()
}

See also CaptureSession, Camera, ScreenCapture, WindowCapture, AudioInput, and ImageCapture.

Property Documentation

actualLocation : QUrl [read-only]

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.


audioBitRate : int [since 6.6]

This property holds the bit rate of the compressed audio stream in bits per second.

This property was introduced in Qt 6.6.


audioChannelCount : int [since 6.6]

This property holds the number of audio channels.

This property was introduced in Qt 6.6.


audioSampleRate : int [since 6.6]

This property holds the audio sample rate in Hz.

This property was introduced in Qt 6.6.


duration : qint64 [read-only]

This property holds the recorded media duration in milliseconds.


encodingMode : enumeration [since 6.6]

This property holds the encoding mode.

This property was introduced in Qt 6.6.

See also QMediaRecorder::EncodingMode.


error : enumeration [read-only]

This property holds the current media recorder error state.

ConstantDescription
MediaRecorder.NoErrorNot in an error state.
MediaRecorder.ResourceErrorNot enough system resources
MediaRecorder.FormatErrorthe current format is not supported.
MediaRecorder.OutOfSpaceErrorNo space left on device.
MediaRecorder.LocationNotWriteableThe output location is not writable.

errorString : string [read-only]

This property holds a string describing the current error state.

See also error.


mediaFormat : MediaFormat

This property holds the current MediaFormat of the recorder.


metaData : mediaMetaData

This property holds meta data associated with the recording.

When a recording is started, any meta-data assigned will be attached to that recording.

Note: Ensure that meta-data is assigned correctly by assigning it before starting the recording.

See also mediaMetaData.


outputLocation : QUrl

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 location can be relative or empty. If empty the recorder uses the system specific place and file naming scheme.

See also errorOccurred().


quality : enumeration

Enumerates quality encoding levels.

ConstantValue
MediaRecorder.VeryLowQuality
MediaRecorder.LowQuality
MediaRecorder.NormalQuality
MediaRecorder.HighQuality
MediaRecorder.VeryHighQuality

recorderState : enumeration [read-only]

This property holds the current media recorder state.

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

ConstantDescription
MediaRecorder.StoppedStateThe recorder is not active.
MediaRecorder.RecordingStateThe recording is requested.
MediaRecorder.PausedStateThe recorder is pause.

videoBitRate : int [since 6.6]

This property holds the bit rate of the compressed video stream in bits per second.

This property was introduced in Qt 6.6.


videoFrameRate : real [since 6.6]

This property holds the video frame rate.

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.

This property was introduced in Qt 6.6.


videoResolution : Size [since 6.6]

This property holds the resolution of the encoded video.

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

This property was introduced in Qt 6.6.


Signal Documentation

actualLocationChanged(const QUrl &location)

Signals that the actual location of the recorded media has changed.

This signal is usually emitted when recording starts.

Note: The corresponding handler is onActualLocationChanged.


durationChanged(qint64 duration)

Signals that the duration of the recorded media has changed.

Note: The corresponding handler is onDurationChanged.


errorOccurred(Error error, const QString &errorString)

Signals that an error has occurred.

The errorString contains a description of the error.

Note: The corresponding handler is onErrorOccurred.


metaDataChanged()

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

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

Note: The corresponding handler is onMetaDataChanged.


recorderStateChanged(RecorderState state)

Signals that a media recorder's state has changed.

Note: The corresponding handler is onRecorderStateChanged.


Method Documentation

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.


record()

Starts recording.

While the recorder state is changed immediately to MediaRecorder.RecordingState, recording may start asynchronously.

If recording fails, the 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 the Window and unlock it again once the recording is finished.


stop()

Stops the recording.

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.


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