QAudioSource¶

The QAudioSource class provides an interface for receiving audio data from an audio input device. More…

Synopsis¶

Functions¶

def bufferSize ()
def bytesAvailable ()
def elapsedUSecs ()
def error ()
def format ()
def isNull ()
def processedUSecs ()
def reset ()
def resume ()
def setBufferSize (bytes)
def setVolume (volume)
def start ()
def start (device)
def state ()
def stop ()
def suspend ()
def volume ()

Signals¶

def stateChanged (state)

Detailed Description¶

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

To record to a file:

QAudioSource lets you record audio with an audio input device. The default constructor of this class will use the systems default audio device, but you can also specify a QAudioDevice for a specific device. You also need to pass in the QAudioFormat in which you wish to record.

Starting up the QAudioSource is simply a matter of calling start() with a QIODevice opened for writing. For instance, to record to a file, you can:

destinationFile = QFile()
QAudioSource* audio # Class member        destinationFile.setFileName("/tmp/test.raw")
destinationFile.open( QIODevice.WriteOnly | QIODevice.Truncate )
format = QAudioFormat()
# Set up the desired format, for example:
format.setSampleRate(8000)
format.setChannelCount(1)
format.setSampleFormat(QAudioFormat.UInt8)
info = QMediaDevices.defaultAudioInput()
if (not info.isFormatSupported(format)) {
    qWarning() << "Default format not supported, trying to use the nearest."

audio = QAudioSource(format, self)
connect(audio, SIGNAL(stateChanged(QAudio.State)), self, SLOT(handleStateChanged(QAudio.State)))
QTimer.singleShot(3000, self, SLOT(stopRecording()))
audio.start(destinationFile)
# Records audio for 3000ms

This will start recording if the format specified is supported by the input device (you can check this with isFormatSupported() . In case there are any snags, use the error() function to check what went wrong. We stop recording in the stopRecording() slot.

def stopRecording(self):

    audio.stop()
    destinationFile.close()
    del audio

At any point in time, QAudioSource will be in one of four states: active, suspended, stopped, or idle. These states are specified by the State enum. You can request a state change directly through suspend() , resume() , stop() , reset() , and start() . The current state is reported by state() . QAudioSink will also signal you when the state changes ( stateChanged() ).

QAudioSource provides several ways of measuring the time that has passed since the start() of the recording. The processedUSecs() function returns the length of the stream in microseconds written, i.e., it leaves out the times the audio input was suspended or idle. The elapsedUSecs() function returns the time elapsed since start() was called regardless of which states the QAudioSource has been in.

If an error should occur, you can fetch its reason with error() . The possible error reasons are described by the Error enum. The QAudioSource will enter the StoppedState when an error is encountered. Connect to the stateChanged() signal to handle the error:

def handleStateChanged(self, newState):

    switch (newState) {
        QAudio.StoppedState: = case()
            if (audio.error() != QAudio.NoError) {
                # Error handling
            else:
                # Finished recording

            break
        QAudio.ActiveState: = case()
            # Started recording - read from IO device
            break
        default:
            # ... other cases as appropriate
            break

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