When the sound design is targeted for 5.1, most of the dialogue comes from the center speaker.
This is great if you have one.
However if its downmixed on the fly (ie done on the client side) the center channel is often just played out of both speakers. This means that sound can be muffled, because its drowned out by the incidental noise that comes from the left/right channel.
When you master for 5.1, because you have the centre speaker, you can have dialogue at 100% volume, then out of left and right, you can have incidental noise, be that music or "atmosphere" also at 100%
(its been a while since I've mastered in 5.1) However, two channels of 100% volume (well 0dbu) is louder than just one channel. Which means that if you have lots of music, wind or other foley it'll drown out the dialogue.
It requires artistic choices from the sound team to make work properly.
Yeah I read the same comment you did, but if you're taking a signal with 6 channels, and only have two channels out, you don't really have any option but send the middle channel to both outputs, else it'll sound far too intense in a single ear.
You mix the dialog louder for the entire piece, and every other sound in the middle. No extreme highs, no extreme lows. General compression with dialog forward choices.
I don't know why compression isn't built in to consumer media devices, it's so often called for (and closely followed by volume normalisation ... but I guess the advertisers veto that).
Blueray supports downmix metadata that I think lets you mix volumes with the full 6x2 matrix, and I don't remember if there's EQ but there may be. Also a 5.1 AV is like 500 bucks if you have the space. I don't think what other innovations you need. The technology to stream different audio streams and let the user choose is there.
Thing is most studios now do only one mix for theaters and also most streaming providers don't give many fucks about audio. It's not an innovation problem it's a product problem.
This is great if you have one.
However if its downmixed on the fly (ie done on the client side) the center channel is often just played out of both speakers. This means that sound can be muffled, because its drowned out by the incidental noise that comes from the left/right channel.