Wouldn't it be great if AirServer could work like an Apple TV and an AirPort express, both at the same time?
With this option you can enable both these features into AirServer. Once this option is enabled, you will see two AirPlay endpoints available for your Mac. One regular AirPlay receiver and one audio-only receiver suffixed with an "Ex" in the end.
Use this feature if you want to keep watching a video on your iOS device and want to send only the audio-only part of the video to your Mac running AirServer.
Streaming to the audio-only part of AirServer also forces the iOS device to send audio in lossless quality as opposed to AAC compressed audio.