QMediaDevices Class

Detailed Description

The QMediaDevices class provides information about the available multimedia devices and the system defaults. It monitors the following three groups:

• Audio input devices (Microphones)
• Audio output devices (Speakers, Headsets)
• Video input devices (Cameras)

QMediaDevices provides a separate list for each device group. If it detects that a new device has been connected to the system or an attached device has been disconnected from the system, it will update the corresponding device list and emit a signal notifying about the change.

The QMediaDevices::audioInputs and QMediaDevices::audioOutputs functions can be used to enumerate all microphones and speakers/headsets on the system. This example first gets a list of all connected microphones, and then prints their identifier, description, and if it is the default device or not.

 const QList<QAudioDevice> audioDevices = QMediaDevices::audioInputs();
 for (const QAudioDevice &device : audioDevices)
 {
     out << "ID: " << device.id() << Qt::endl;
     out << "Description: " << device.description() << Qt::endl;
     out << "Is default: " << (device.isDefault() ? "Yes" : "No") << Qt::endl;
 }

Similarly, the QMediaDevices::videoInputs will return a list of all connected cameras. In this example we list all connected cameras and their identifier, description, and if it is the default camera or not.

 const QList<QCameraDevice> videoDevices = QMediaDevices::videoInputs();
 for (const QCameraDevice &device : videoDevices)
 {
     out << "ID: " << device.id() << Qt::endl;
     out << "Description: " << device.description() << Qt::endl;
     out << "Is default: " << (device.isDefault() ? "Yes" : "No") << Qt::endl;
 }

QMediaDevices monitors the system defaults for each device group. It will notify about any changes done through the system settings. For example, if the user selects a new default audio output in the system settings, QMediaDevices will update the default audio output accordingly and emit a signal. If the system does not provide a default for a camera or an audio input, QMediaDevices will select the first device from the list as the default device.

While using the default input and output devices is often sufficient for playing back or recording multimedia, there is often a need to explicitly select the device to be used.

QMediaDevices is a singleton object and all getters are thread-safe.