High Sierra Airplay Problems

I've been using a Mac running Sierra with an Airplay 2 capable Denon home cinemas amp for several months without any major problems.

After upgrading to High Sierra I've run into two VERY annoying issues:

• Whenever I switch audio output from internal speaker to the Airplay amp and then hit play in a Youtube video or other video player iTunes starts instead of the video playing! I have to quit iTunes and hit play again before it actually starts playing
• Whenever playback starts all open network connections drop.

Does anybody know how to stop iTunes autostarting when I switch to Airplay as the output device, and how to stop the connections from dropping? Neither of these things happened in Sierra.

EDIT: I tried getting a list of audio devices and AirPlay doesn't show up at all.

system_profiler SPAudioDataType Audio:

Devices:

    Built-in Output:

      Default Output Device: Yes
      Default System Output Device: Yes
      Manufacturer: Apple Inc.
      Output Channels: 2
      Current SampleRate: 44100
      Transport: Built-in
      Output Source: Internal Speakers

    iShowU Audio Capture:

      Default Input Device: Yes
      Input Channels: 2
      Manufacturer: shinywhitebox ltd.
      Output Channels: 2
      Current SampleRate: 44100
      Transport: Unknown
      Input Source: Default
      Output Source: Default

    Stream/Record:

      Manufacturer: Apple Inc.
      Output Channels: 2
      Current SampleRate: 44100
      Transport: Unknown
      Output Source: Default

However "Denon AVR-6400H" shows up as an available output device in the audio prefs pane and in the icon menu options.

Solution 1:

That's probably because High Sierra introduced AirPlay2 (before, you were running AirPlay). With AirPlay2, it's no more a system wide output that's being redirected to your remote player, but instead a per-application output. Technically speaking, it's now a userspace library that application must implement.

Since only iTunes supports AirPlay2 for now, I guess this is the reason why it's being launched.

As to how to disable this, please check if your player can disable its AirPlay2 announce or use iTunes...