Dolby Atmos: thoughts on mixing for Atmos as it pertains to 7.1 & 5.1 systems.

[J. PUPSTER]

I recall not long ago dissecting the bed (floor) channels of an Atmos rip from a song off the Rolling Stones release Hackney Diamonds Blu-ray; and noticed what could be perceived as problematic mixing choices, if you don't have a full (7.1.4) Atmos system or even just an 7.1 system.
Here's the link to that post (I later learned that in Audacity channels 5&6 were actually the rears "Rear Surround" and 7&8 are the sides "Surrounds"):
https://www.quadraphonicquad.com/fo...tmos-blu-ray-box-set.34753/page-7#post-733813

So actually, that mostly isolated Piano (at a somewhat relatively low amplitude I might add) would appear in the Rears or "Rear Surrounds" of a full 7.1.4 or 7.1 speaker system.
As we should know by now, the full Atmos with height information is embedded in the 7.1 floor and then up-folded into the heights when someone with height speakers and an Atmos capable AVR processes the metadata allowing the information to come forth correctly. Shouldn't be a problem, however when someone like myself only has a standard 5.1 system with no Atmos handling capabilities there could be other issues with the mix that aren't immediately apparent. In this case the lovely low level Piano in a 5.1 system is relegated to be down mixed by my oppo BD or a receiver, into the Sides "Surrounds" where it has to compete with the distorted rhythm guitars (lower amplitude of the Piano combined with whatever frequency range conflicts that might occur.) As such and IMO, the Piano gets mostly buried in the mix. It is possible I suppose with my advanced age and level of hearing, I'm just not able to "pick it out of the mix" as easily as someone with much better hearing. But I do contend that when something like that happens, it very well could be muddying things up; and that the mixing engineer should consider that situation.

I'll open the floor now for discussion

 

[austinsignal]

I recall not long ago dissecting the bed (floor) channels of an Atmos rip from a song off the Rolling Stones release Hackney Diamonds Blu-ray; and noticed what could be perceived as problematic mixing choices, if you don't have a full (7.1.4) Atmos system or even just an 7.1 system.
Here's the link to that post (I later learned that in Audacity channels 5&6 were actually the rears "Rear Surround" and 7&8 are the sides "Surrounds"):
https://www.quadraphonicquad.com/fo...tmos-blu-ray-box-set.34753/page-7#post-733813

So actually, that mostly isolated Piano (at a somewhat relatively low amplitude I might add) would appear in the Rears or "Rear Surrounds" of a full 7.1.4 or 7.1 speaker system.
As we should know by now, the full Atmos with height information is embedded in the 7.1 floor and then up-folded into the heights when someone with height speakers and an Atmos capable AVR processes the metadata allowing the information to come forth correctly. Shouldn't be a problem, however when someone like myself only has a standard 5.1 system with no Atmos handling capabilities there could be other issues with the mix that aren't immediately apparent. In this case the lovely low level Piano in a 5.1 system is relegated to be down mixed by my oppo BD or a receiver, into the Sides "Surrounds" where it has to compete with the distorted rhythm guitars (lower amplitude of the Piano combined with whatever frequency range conflicts that might occur.) As such and IMO, the Piano gets mostly buried in the mix. It is possible I suppose with my advanced age and level of hearing, I'm just not able to "pick it out of the mix" as easily as someone with much better hearing. But I do contend that when something like that happens, it very well could be muddying things up; and that the mixing engineer should consider that situation.

I'll open the floor now for discussion

When mixing in ATMOS (assuming in 7.1.4 or greater), imho it's important to check 5.1 to see how the downmix translates - obviously it's important to hear what's happening to heights and rears. When finalizing an ATMOS mix, there are downmix controls that are adjustable on a per-song basis (see attached). I tend to use all the space available generally, so there's typically a lot up top and behind when I mix - and sometimes that stuff needs adjusting for 5.1....so the downmix controls can help make things a little more coherent in 5.1. It ain't perfect, but it can help. I will say that a fair number of people mixing leave the surround and height trims set to '0' and leave it at that. No idea what's happening with the piano part you mention; impossible to tell without running the master (ADM) in the Dolby Renderer, but it may have been 'improvable' with downmix settings.

In general, all kinds of tonal weirdness happens when one spreads tracks out in the ATMOS space. For instance, if you widen a drum stem out, say, further from it's normal stereo/LR position into the sides (or up!) , the 'click' of a kick drum can disappear, snare drums can change in tone etc. ATMOS makes decisions about tonality based location in space, which can really be a challenge. If mixing from stems, and trying to match eq, etc with the stereo master, all kinds of tricks can be employed to take advantage of the 3D space and at the same time keep the tonality of the stereo master. Combine all this with downmix placement in 5.1, and it makes for a LOT of checking/adjusting. And don't even get me started on then checking headphones - 7.1.4 --> 5.1 --> Binaural headphones --> Apple Spatial headphones ....lots of check-re-check-check-re-check....It's obviously easier to just take the 'ambient' mix approach and leave things generally in the traditional stereo field and add surround reverb/delays to give a sense of space. But what fun is that?

Clearly there are imperfections in translation to various downmixes and lots to evaluate when mixing, but I find what Dolby has done as absolutely miraculous overall. Incredible.