I don't really know much about this as would be evident from my stupid question. But I was watching a movie using Emby and this questions popped into my head and what better place to ask then on Reddit :) Basically this movie has few audio tracks one of which is 7.1 and other ones were 5.1. Now the setup we have is Fire Stick 4K plugged into Yamaha RXV-685 which basically plugs into a cheap 4K Toshiba TV we have. We have a 5.1 surround sound setup using Acoustic speakers. This is the first time I actually played a movie that had 7.1 as default audio. It made me think although we only have 5.1 setup, RXV685 would kick in and use convert 7.1 into the audio for 5.1 or should I simply select 5.1 AAC?

2) 2nd question on a similar note, if a movie or show has multiple audio tracks like one for 7.1 and another for 5.1, if these are however played using just 5.1 surround sound setup, would there a quality difference between the two tracks? To rephrase say the centre speaker which is usually used for dialogue and is available in pretty much every surround sound setup, would there be a discernible quality difference if 7.1 audio was being played in contrast to 5.1 track via that speaker?