iOS - Surround sound not working correctly over lightning to HDMI Adapter

[phunkyfish]

Tested using an iPhone X connected to a denon 7.1 sound system.

• 2.0 is just garbled for any format.
• Setting 5.1 or 7.1 it sounds ok but the speaker output is not correct.
• Left, left rear and sub play the same. Centre, right and right rear play the same.

So it's like it's forcing everything to 2 channels across 2 groups of speakers.

[phunkyfish]

Tested using 5.1 speaker test videos.

[phunkyfish]

Discovered when trying to port the audiosink upstream: xbmc/xbmc#16015