Play N videos in sync

This is a toy app to try and understand how many videos I can play simultaneously on iOS. Some forums say it's 4. I seem to hit a limit at 16.

Behaviours to try out:

• Can I quickly toggle between several videos within a same AVPlayerLayer, with random seekTimes?
• Can I sync video playback on an external clock (driven by the audio render callback, for instance)?

Links

• This guy also observes 16 vids as a max
• The four streams limit seems to be unofficially admitted by Apple
• Some dev hints from the Pinterest engineers
• WWDC presentation #517 on syncing players with clocks