class QAudioSink

The QAudioSink class provides an interface for sending audio data to an audio output device. More

Inheritance diagram of PySide6.QtMultimedia.QAudioSink

Synopsis

Methods

Signals

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

You can construct an audio output with the system’s default audio output device. It is also possible to create QAudioSink with a specific QAudioDevice . When you create the audio output, you should also send in the QAudioFormat to be used for the playback (see the QAudioFormat class description for details).

To play a file:

Starting to play an audio stream is simply a matter of calling start() with a QIODevice. QAudioSink will then fetch the data it needs from the io device. So playing back an audio file is as simple as:

QFile sourceFile # class member.
QAudioSink* audio # class member.
sourceFile.setFileName("/tmp/test.raw")
sourceFile.open(QIODevice.ReadOnly)
format = QAudioFormat()
# Set up the format, eg.
format.setSampleRate(8000)
format.setChannelCount(1)
format.setSampleFormat(QAudioFormat.UInt8)
info = QAudioDevice(QMediaDevices.defaultAudioOutput())
if not info.isFormatSupported(format):
    qWarning() << "Raw audio format not supported by backend, cannot play audio."
    return

audio = QAudioSink(format, self)
audio.connect(QAudioSink::stateChanged, self.handleStateChanged)
audio.start(sourceFile)

The file will start playing assuming that the audio system and output device support it. If you run out of luck, check what’s up with the error() function.

After the file has finished playing, we need to stop the device:

def stopAudioOutput(self):

    audio.stop()
    sourceFile.close()
    del audio

At any given time, the QAudioSink will be in one of four states: active, suspended, stopped, or idle. These states are described by the State enum. State changes are reported through the stateChanged() signal. You can use this signal to, for instance, update the GUI of the application; the mundane example here being changing the state of a play/pause button. You request a state change directly with suspend() , stop() , reset() , resume() , and start() .

If an error occurs, you can fetch the error type with the error() function. Please see the Error enum for a description of the possible errors that are reported. When UnderrunError is encountered, the state changes to IdleState , when another error is encountered, the state changes to StoppedState . You can check for errors by connecting to the stateChanged() signal:

def handleStateChanged(self, newState):


        if newState == QAudio.IdleState:
            # Finished playing (no more data)
            AudioOutputExample::stopAudioOutput()
            break
        elif newState == QAudio.StoppedState:
            # Stopped for other reasons
            if audio.error() != QAudio.NoError:
                # Error handling

            break
        else:
            # ... other cases as appropriate
            break
__init__([format=QAudioFormat()[, parent=None]])
Parameters:

Construct a new audio output and attach it to parent. The default audio output device is used with the output format parameters.

__init__(audioDeviceInfo[, format=QAudioFormat()[, parent=None]])
Parameters:

Construct a new audio output and attach it to parent. The device referenced by audioDevice is used with the output format parameters.

bufferSize()
Return type:

int

Returns the audio buffer size in bytes.

If called before start() , returns platform default value. If called before start() but setBufferSize() was called prior, returns value set by setBufferSize() . If called after start() , returns the actual buffer size being used. This may not be what was set previously by setBufferSize() .

See also

setBufferSize()

bytesFree()
Return type:

int

Returns the number of free bytes available in the audio buffer.

Note

The returned value is only valid while in ActiveState or IdleState state, otherwise returns zero.

elapsedUSecs()
Return type:

int

Returns the microseconds since start() was called, including time in Idle and Suspend states.

error()
Return type:

Error

Returns the error state.

format()
Return type:

QAudioFormat

Returns the QAudioFormat being used.

isNull()
Return type:

bool

Returns true is the QAudioSink instance is null, otherwise returns false.

processedUSecs()
Return type:

int

Returns the amount of audio data processed since start() was called (in microseconds).

reset()

Drops all audio data in the buffers, resets buffers to zero.

resume()

Resumes processing audio data after a suspend() .

Sets state() to the state the sink had when suspend() was called, and sets error() to QAudioError::NoError. This function does nothing if the audio sink’s state is not SuspendedState .

setBufferSize(bytes)
Parameters:

bytes – int

Sets the audio buffer size to value in bytes.

Note

This function can be called anytime before start() . Calls to this are ignored after start() . It should not be assumed that the buffer size set is the actual buffer size used - call bufferSize() anytime after start() to return the actual buffer size being used.

See also

bufferSize()

setVolume(arg__1)
Parameters:

arg__1 – float

Sets the output volume to volume.

The volume is scaled linearly from 0.0 (silence) to 1.0 (full volume). Values outside this range will be clamped.

The default volume is 1.0.

Note

Adjustments to the volume will change the volume of this audio stream, not the global volume.

UI volume controls should usually be scaled non-linearly. For example, using a logarithmic scale will produce linear changes in perceived loudness, which is what a user would normally expect from a volume control. See convertVolume() for more details.

See also

volume()

start()
Return type:

QIODevice

Returns a pointer to the internal QIODevice being used to transfer data to the system’s audio output. The device will already be open and write() can write data directly to it.

Note

The pointer will become invalid after the stream is stopped or if you start another stream.

If the QAudioSink is able to access the system’s audio device, state() returns IdleState , error() returns NoError and the stateChanged() signal is emitted.

If a problem occurs during this process, error() returns OpenError , state() returns StoppedState and the stateChanged() signal is emitted.

See also

QIODevice

start(device)
Parameters:

deviceQIODevice

Starts transferring audio data from the device to the system’s audio output. The device must have been opened in the ReadOnly or ReadWrite modes.

If the QAudioSink is able to successfully output audio data, state() returns ActiveState , error() returns NoError and the stateChanged() signal is emitted.

If a problem occurs during this process, error() returns OpenError , state() returns StoppedState and the stateChanged() signal is emitted.

See also

QIODevice

state()
Return type:

State

Returns the state of audio processing.

stateChanged(state)
Parameters:

stateState

This signal is emitted when the device state has changed. This is the current state of the audio output.

Note

The QtAudio namespace was named QAudio up to and including Qt 6.6. String-based connections to this signal have to use QAudio::State as the parameter type: connect(source, SIGNAL(stateChanged(QAudio::State)), ...);

stop()

Stops the audio output, detaching from the system resource.

Sets error() to NoError , state() to StoppedState and emit stateChanged() signal.

Note

On Linux, and Darwin, this operation synchronously drains the underlying audio buffer, which may cause delays accordingly to the buffer payload. To reset all the buffers immediately, use the method reset instead.

See also

reset()

suspend()

Stops processing audio data, preserving buffered audio data.

Sets error() to NoError , state() to SuspendedState and emits stateChanged() signal.

volume()
Return type:

float

Returns the volume between 0.0 and 1.0 inclusive.

See also

setVolume()