Control events

You may have an application that needs to monitor audio management events and be notified when an event occurs.

These events track active audio streams and let you know what audio types are active on the system. You have to call snd_ctl_read() after the select() to read the event from the queue. If it's a SND_CTL_READ_AUDIOMGMT_CHG event, then use snd_ctl_ducking_read() to read the audio management status. Any audio that has been ducked to zero or has been preempted (e.g., in the SUSPENDED state) is considered not to be active.
Note: Audio streams that have been user-paused (e.g., snd_pcm_*_pause()) are considered active.

For an example of how to monitor events and determine the state of active audio streams on the system, see the audiomgmt_monitor.c example appendix. As part of using control events, you can specify the ducking outputs that you want to monitor. You can specify the name as a [CTRL] key in the audio configuration file or as a option when you start io-audio. For more information, see io-audio in the Utilities Reference.