QAudioInput

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

Inheritance diagram of PySide2.QtMultimedia.QAudioInput

Synopsis

Functions

Signals

Detailed Description

You can construct an audio input with the system’s default audio input device . It is also possible to create QAudioInput with a specific QAudioDeviceInfo . 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:

QAudioInput 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 QAudioDeviceInfo for a specific device. You also need to pass in the QAudioFormat in which you wish to record.

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

    QFile destinationFile;   // Class member
    QAudioInput* audio; // Class member
{
    destinationFile.setFileName("/tmp/test.raw");
    destinationFile.open( QIODevice::WriteOnly | QIODevice::Truncate );

    QAudioFormat format;
    // Set up the desired format, for example:
    format.setSampleRate(8000);
    format.setChannelCount(1);
    format.setSampleSize(8);
    format.setCodec("audio/pcm");
    format.setByteOrder(QAudioFormat::LittleEndian);
    format.setSampleType(QAudioFormat::UnSignedInt);

    QAudioDeviceInfo info = QAudioDeviceInfo::defaultInputDevice();
    if (!info.isFormatSupported(format)) {
        qWarning() << "Default format not supported, trying to use the nearest.";
        format = info.nearestFormat(format);
    }

    audio = new QAudioInput(format, this);
    connect(audio, SIGNAL(stateChanged(QAudio::State)), this, SLOT(handleStateChanged(QAudio::State)));

    QTimer::singleShot(3000, this, 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.

void AudioInputExample::stopRecording()
{
    audio->stop();
    destinationFile.close();
    delete audio;
}

At any point in time, QAudioInput 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() . QAudioOutput will also signal you when the state changes ( stateChanged() ).

QAudioInput 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 QAudioInput 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 QAudioInput will enter the StoppedState when an error is encountered. Connect to the stateChanged() signal to handle the error:

void AudioInputExample::handleStateChanged(QAudio::State newState)
{
    switch (newState) {
        case QAudio::StoppedState:
            if (audio->error() != QAudio::NoError) {
                // Error handling
            } else {
                // Finished recording
            }
            break;

        case QAudio::ActiveState:
            // Started recording - read from IO device
            break;

        default:
            // ... other cases as appropriate
            break;
    }
}
class PySide2.QtMultimedia.QAudioInput(audioDeviceInfo[, format=QAudioFormat()[, parent=None]])

PySide2.QtMultimedia.QAudioInput([format=QAudioFormat()[, parent=None]])

param parent

PySide2.QtCore.QObject

param audioDeviceInfo

PySide2.QtMultimedia.QAudioDeviceInfo

param format

PySide2.QtMultimedia.QAudioFormat

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

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

PySide2.QtMultimedia.QAudioInput.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()

PySide2.QtMultimedia.QAudioInput.bytesReady()
Return type

int

Returns the amount of audio data available to read in bytes.

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

PySide2.QtMultimedia.QAudioInput.elapsedUSecs()
Return type

int

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

PySide2.QtMultimedia.QAudioInput.error()
Return type

Error

Returns the error state.

PySide2.QtMultimedia.QAudioInput.format()
Return type

PySide2.QtMultimedia.QAudioFormat

Returns the QAudioFormat being used.

PySide2.QtMultimedia.QAudioInput.notify()
PySide2.QtMultimedia.QAudioInput.notifyInterval()
Return type

int

Returns the notify interval in milliseconds.

PySide2.QtMultimedia.QAudioInput.periodSize()
Return type

int

Returns the period size in bytes.

Note: This is the recommended read size in bytes.

PySide2.QtMultimedia.QAudioInput.processedUSecs()
Return type

int

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

PySide2.QtMultimedia.QAudioInput.reset()

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

PySide2.QtMultimedia.QAudioInput.resume()

Resumes processing audio data after a suspend() .

Sets error() to NoError . Sets state() to ActiveState if you previously called start( QIODevice *). Sets state() to IdleState if you previously called start() . emits stateChanged() signal.

PySide2.QtMultimedia.QAudioInput.setBufferSize(bytes)
Parameters

bytes – int

Sets the audio buffer size to value 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, calling bufferSize() anytime after start() will return the actual buffer size being used.

See also

bufferSize()

PySide2.QtMultimedia.QAudioInput.setNotifyInterval(milliSeconds)
Parameters

milliSeconds – int

Sets the interval for notify() signal to be emitted. This is based on the ms of audio data processed not on actual real-time. The minimum resolution of the timer is platform specific and values should be checked with notifyInterval() to confirm actual value being used.

See also

notifyInterval()

PySide2.QtMultimedia.QAudioInput.setVolume(volume)
Parameters

volume – float

Sets the input volume to volume .

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

If the device does not support adjusting the input volume then volume will be ignored and the input volume will remain at 1.0.

The default volume is 1.0 .

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

See also

volume()

PySide2.QtMultimedia.QAudioInput.start(device)
Parameters

devicePySide2.QtCore.QIODevice

Starts transferring audio data from the system’s audio input to the device . The device must have been opened in the WriteOnly , Append or ReadWrite modes.

If the QAudioInput is able to successfully get audio data, state() returns either ActiveState or 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

PySide2.QtMultimedia.QAudioInput.start()
Return type

PySide2.QtCore.QIODevice

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

Note

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

If the QAudioInput 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

PySide2.QtMultimedia.QAudioInput.state()
Return type

State

Returns the state of audio processing.

PySide2.QtMultimedia.QAudioInput.stateChanged(state)
Parameters

stateState

PySide2.QtMultimedia.QAudioInput.stop()

Stops the audio input, detaching from the system resource.

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

PySide2.QtMultimedia.QAudioInput.suspend()

Stops processing audio data, preserving buffered audio data.

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

PySide2.QtMultimedia.QAudioInput.volume()
Return type

float

Returns the input volume.

If the device does not support adjusting the input volume the returned value will be 1.0.

See also

setVolume()