Audio constraints. Audio device will be chosen according to these settings. Settings are specified via AudioDeviceManager.setDefaultAudioSettings and AudioDeviceManager.setCallAudioSettings.
If this value is a true or false, the user agent will attempt to obtain media with automatic gain control enabled or disabled as specified, if possible.
Should participant's echo be cancelled or not? If it's true, echo is cancelled; it's true by default.
Unique ID of microphone. It can be received via the AudioDeviceManager.getInputDevices method.
If it's true, backgroung noise is suppressed. It's true by default.
Unique ID of a sound card/processor. It can be received via the AudioDeviceManager.getOutputDevices method.
If it's true, all audio settings must suit each other strictly; the incorrect settings will cause an error. If it's false, the incorrect values will be changed to the best appropriate values. It's false by default.