Audio tracks from several AVPlayer instances mixed when using AirPlay for only one of them

[defagos]

When using AirPlay with a single non-muted AVPlayer instance enabled for external playback, with other sibling instances muted and not enabled for external playback, audio tracks of all instances are mixed on the AirPlay receiver.

This seems to be a regression which appeared with AirPlay 2:

• https://forums.developer.apple.com/thread/105877
• https://stackoverflow.com/questions/19797618/airplay-with-multiple-instances-of-avplayer

There might be no simple fix to this issue.

Issue type

Incorrect behavior

Environment information

I tested with devices probably using AirPlay 2:

• Library version: 3.0.0
• iOS version: 13
• Device: iPhone XS with Apple TV 1080p

Reproducibility

Always reproducible

Steps to reproduce

1. Open the multiplayer demo.
2. Enable AirPlay
3. Listen