Atmos Playback In 5.1

[Sal1950]

No, not at all. Atmos was obviously designed for cinemas. Music and streaming were afterthoughts.

Exactly. Atmos was in the cinema and on HT BluRay almost a decade before streaming came to be.

 

[barfle]

I don't know enough about Atmos so I need to ask this. If a recording comes out in Atmos only, does it down scale to 5.1 if you don't have Atmos?

As I understand the process (and it’s a bit cryptic), Atmos generally starts with a 5.1 or 7.1 bed, then with metadata removes various sounds from that bed and places them as objects in a designated location in the soundfield. I am fully aware that explanation leaves a lot out of the process of making Atmos, and if anyone wishes to expand on it, well, you may have more time on your hands today than I do.

 

[madscot]

yup..we have opinions. My ears are mine Yes..Dolby Atmos was most likely designed for streaming.. Isn't that obvious?

Most people who “stream” music listen on one or two speakers or headphones, i’d say 99% of people with atmos speakers have a home theatre system

 

[AYanguas]

I don't know enough about Atmos so I need to ask this. If a recording comes out in Atmos only, does it down scale to 5.1 if you don't have Atmos?

As I understand the process (and it’s a bit cryptic), Atmos generally starts with a 5.1 or 7.1 bed, then with metadata removes various sounds from that bed and places them as objects in a designated location in the soundfield. I am fully aware that explanation leaves a lot out of the process of making Atmos, and if anyone wishes to expand on it, well, you may have more time on your hands today than I do.

I made a somewhat more extensive explanation here:
https://www.quadraphonicquad.com/fo...tmos-parts-appear-in-stereo.35022/post-741118

 

[AYanguas]

When I can compare a 5.1 DTS MA to an Atmo version of same ('folded'' to 5.1)s ....make no mistake, it sounds like crap compared to the DTS 5.1 version on same titles. At least the ones we own. DTS has been squeezed out now, almost completely and so have we..... Nothing 'tricky' at all. Just the simple truth.

When a Blu-ray release have both Dolby Atmos track and 5.1 track, this is usually because the mixing engineer has made an independent mix adapted to 5.1 so that it sounds better than the 5.1 substream present in the TrueHD Atmos that is automatically generated from the original raw mix to the consumer format TrueHD Atmos

 

[AYanguas]

This is a good “White Paper” (only 15 pages) that can be useful to understand why and how Dolby Atmos was created and how it works:

https://professional.dolby.com/siteassets/tv/home/dolby-atmos/dolby-atmos-for-home-theater.pdf

I think that everyone interested in this topic, who has questions or doubts about it, should read it.

 

[J. PUPSTER]

Perhaps a lot of confusion about “down mixed” & “folded down” is due from point of view; either the person actually mixing the data information compared to the listening consumers. The listening consumer’s gear may be only 7.1 with all Atmos info already in those floor channels. 5.1 listeners get the 7.1 floor down mixed. If the consumer has Atmos gear (with height capability) then the 7.1 is “up folded.”

 

[J. PUPSTER]

Perhaps a lot of confusion about “down mixed” & “folded down” is due from point of view; either the person actually mixing the data information compared to the listening consumers. The listening consumer’s gear may be only 7.1 with all Atmos info already in those floor channels. 5.1 listeners get the 7.1 floor down mixed. If the consumer has Atmos gear (with height capability) then the 7.1 is “up folded.”

maybe even better to say the 7.1 is “unfolded up”

 

[barfle]

This is a good “White Paper” (only 15 pages) that can be useful to understand why and how Dolby Atmos was created and how it works:

https://professional.dolby.com/siteassets/tv/home/dolby-atmos/dolby-atmos-for-home-theater.pdf

I think that everyone interested in this topic, who has questions or doubts about it, should read it.

I will print it out and read it. Thank you.

 

[fourml8r]

Atmos is made up of 2 parts, the bed layer and a separate metadata signal that tells the processor where to place the Atmos sounds. When you do not have Atmos, it is backward compatible and will fold the metadata into the regular bed layer signal. You will have all the same audio components just in a different location

 

[JediJoker]

When you do not have Atmos, it is backward compatible and will fold the metadata into the regular bed layer signal.

Rather, the metadata are ignored and the bed is played as-is, with all elements present.

 

[Sal1950]

i’d say 99% of people with atmos speakers have a home theatre system

A fair enough statement of today I guess.
But like so many here, I started my surround journey to listen to and play back the Quad musical releases of the 1970s, a time when Home Theater hadn't even become a reality yet. It was only decades later with DVD (A few LaserDiscs) that multich movie sound was offered.

 

[himey]

Perhaps a lot of confusion about “down mixed” & “folded down” is due from point of view; either the person actually mixing the data information compared to the listening consumers. The listening consumer’s gear may be only 7.1 with all Atmos info already in those floor channels. 5.1 listeners get the 7.1 floor down mixed. If the consumer has Atmos gear (with height capability) then the 7.1 is “up folded.”

I like your use of floor rather than bed. Bed has a technical meaning (not object), that technically doesn't belong in this discussion, but is used all of the time.

 

[AYanguas]

Rather, the metadata are ignored and the bed is played as-is, with all elements present.

Correct. But what you are referring to is not "the bed".

I like your use of floor rather than bed. Bed has a technical meaning (not object), that technically doesn't belong in this discussion, but is used all of the time.

Correct.

Let's educate a little. Without acrimony, as a Spanish politician said.

The "bed" channels is the Atmos concept of 7.1.2 fixed speakers locations where sounds can be assigned without using "Objects". 7.1 are the known floor channels and the .2 are the Top Middle channels just above the listener. Top Middle channels are bed channels.

The multichannel file TrueHD (7.1) or DD+ (5.1) is seen as having those number of "channels": 7.1 or 5.1

Additionaly, those mch files can contain a substream of metadata. Metadata describes sound content for the Atmos "bed" channels (fixed locations of 7.1.2) and/or Atmos Objects (whatever 3D locations).

When the processor does not decode Atmos it just "ignores" the metadata, because it does not understand it. It does not understand Atmos. Then it only "see" the mch file TrueHD (7.1) or DD+ (5.1) with those number of "channels" (not bed channels). Bed channels is an Atmos concept, and there are No "Bed Channels" if we do not decode Atmos, because we do not understand Atmos. Then the whole content 7.1 or 5.1 is played according to the AVR capacity, as in pre-Atmos era. That 7.1/5.1 substream, as well as the 2.0 substrem are generated when the TrueHD Atmos is rendered from the Master mix and contains ALL mixed sound. But this is done during the consumer TrueHD file creation at the production studio, not during the AVR decoding.

When the AVR processor support Atmos, it reads the metadata substream, and for each sound described in the metadata (3D location and size) (etither bed channel or Object), executes a substraction from the mch file channels substream and an addition to the available Speakers to image the sound 3D location (and size) as better as possible using the available speakers.

If the mix is done using Objects located in 3D space in locations other than bed channels, then as more speakers available the better is achieved as the mixer engineer intended. This way of mixing could be considered as "good" using the available potential of Dolby Atmos.

If the mix is done using only the bed channels, then the mixer engineer is not using the full Atmos potential, and not necessarily the mix could be considered "worse". It would depend on how well he has crafted the sounds for each channel to get the image effects that we know can be achieved, even from just Quad 4.0

Of course, the Objects potential of locating a sound at the 3D coordinates we want and with the "size" we want is more advanced and would get better results if well done, than with just single locations of bed channels.

 

[shokhead]

I believe all blu's that have an Atmos mix also have a dedicated 5.1 mix. At least that's the case in the ones I've bought.

Just bought the blu ray Eric Clapton and the disc is Atmos or stereo.

 

[artwwweb]

I still don't have an Atmos amp and only have 5.1 speakers.

When I've tried a couple of Atmos mixes I found them rear-heavy. I suspect that is because anything that's meant to be in the middle speakers is just sent to the rears. My amp is capable of 7.1 but knows it only has 5.1 speakers so I would have expected it to mix the middle sounds to a phantom middle, i.e. from both front and rear speakers. I don't know whether this is a problem with my amp or is a more general problem. So as a rule I play the 5.1 stream of an Atmos disc if there is one.

I've been disappointed to see that quite a few recent releases that don't have a separate 5.1 stream. I think this is a reflection of the fact that even the remix engineers sometimes don't understand how their mix will sound in 5.1 - I think they believe the hype that will all just magically work.

Question: if I get an Atmos amp but leave my speakers as 5.1 will it create a better sound mapping? I.e. put middle sounds in the phantom middle rather than out of the rear? (I would assume it would. It would be a relatively easy upgrade compared to paying for and installing all those speakers.)

 

[LuvMyQuad]

Just bought the blu ray Eric Clapton and the disc is Atmos or stereo.

I have several releases that do not list a 5.1 mix. But when you rip them, there is a 5.1 core stream embedded in the True HD stream. It's not shown as DD. I'm not sure if it's a dedicated mix or how one would access it..

 

[Stupy]

A heads up generally to this thread https://www.quadraphonicquad.com/fo...ms-tests-results-questions-experiences.29057/

If you can get the test files it will answer once and for all what your system is doing It may also effectively check your software behaviour-?

Before I had Atmos my tests were pleasing in that playback on 5.1 lost nothing and behaved doggedly predictably. I personally determined no point in converting atmos to 5.1 normally as the playback was that reliable and predictable.

 

[AYanguas]

I have several releases that do not list a 5.1 mix. But when you rip them, there is a 5.1 core stream embedded in the True HD stream. It's not shown as DD. I'm not sure if it's a dedicated mix or how one would access it..

The 5.1 substream in a TrueHD file is generated automatically when the TrueHD file is built from the Master file at the production studio. Possibly is optional and not always mandatory. That 5.1 substream is still TrueHD.

It is a kind of automatic "downmix" than contains all sound in the 5.1 mch, for playing retro-compatibility.

This substream ("core" is the terminology for DTS and is a different concept) can be seen by some ripping tools/MkvToolNix/MediaInfo as a separate "track", and eventually could be accessed by that tools. But it cannot be accessed directly by the BD menus. The AVR processor see a single "track" TrueHD and manages the substreams automatically to play for what it is compatible. Possibly setting of "Sound Options" in the AVR could select a non-atmos substring.

IT IS NOT a dedicated mix. If the automatic "downmixing" does not give good results for a particular Atmos mix, some engineers (as Steven Wilson) do usually craft a dedicated 5.1 mix, different than the Atmos mix, that would sound better in a 5.1 system. But some others don't do it.

 

[sjcorne]

I suspect that is because anything that's meant to be in the middle speakers is just sent to the rears.

Yep, I wrote a bit about this here:
https://www.quadraphonicquad.com/fo...ray-in-february-2024.32444/page-5#post-737955