Do this backwards: Where do 5.1 and Atmos parts appear in stereo

[MidiMagic]

I want to know where all of the other channels in a 5.1 discrete and Atmos will appear if I listen to it in:

1. Ordinary stereo.

2. A Dolby 2.1 soundbar.

 

[zeerround]

The short answer is; it depends.

Dolby (and others for their systems) have default mixdown rules, but there is also the ability for producers/engineers to change those, or even have a custom "presentation" mix for lessor systems.

Not sure what would be controlling the mixdown for your "5.1 discrete" use case, as it would depend on the player. Some will reduce the volume of rears and others will not. The way I do 5.1 mixdown would be:

Fronts to L & R
Rears to L & R
Center - 6dB to L & R
LFE - 6dB to L & R

Overall volume normalized after mixdown.

The logic being that C and LFE will be comming from twice the number of speakers, as in the original mix, so we need to halve the volume, in order for the volume at the listening position to be the same as in the 5.1 mix.

Note the -6dB refers to amplitude or voltage, where as half volume in terms of power would be -3dB.

 

[zeerround]

Here you can see some of the options for Dolby Atmos encoding for 2 ch. playback:

 

[zeerround]

More info on Dolby Atmos downmix settings here:

https://professionalsupport.dolby.c...d-Stereo-downmix-settings-work?language=en_US

 

[Sonik Wiz]

I want to know where all of the other channels in a 5.1 discrete and Atmos will appear if I listen to it in:

1. Ordinary stereo.

2. A Dolby 2.1 soundbar.

Do you listen to ATMOS or 5.1 discrete down mixed to stereo?

Do you have a Dolby 2.1 soundbar?

Maybe just curious?

 

[MidiMagic]

I don't have either yet.

I recently played a YouTube Atmos video in stereo and heard some strange sound placements.

I am interested in what it will sound like if I play new media before I have the proper equipment.

I am particularly interested in where the sound images from each channel will end up:

5.1 discrete played through stereo
5.1 discrete played through Pro-Logic I
5.1 discrete played through 2.1 soundbar
Atmos played through stereo
Atmos played through Pro-Logic I
Atmos played through a 2.1 soundbar

I am particularly interested in whether or not the 2.1 soundbar tries to fake surround positions.

 

[jimfisheye]

I want to know where all of the other channels in a 5.1 discrete and Atmos will appear if I listen to it in:

1. Ordinary stereo.

2. A Dolby 2.1 soundbar.

As mentioned, there are downmix rules. This has been a thing for a while now well before Atmos extended the concept.

"Regular stereo" could end up being all left channels to stereo L and all right channels to stereo R. There might be a rule set to lower the rears 3db, for just one example. The idea is the mixer sets and vets this. This extends to lesser surround channel arrays too. Heights folded down to sides and/or rears.

"Atmos binaural stereo" is different and new for Atmos. This downmixes to stereo in a similar way but will apply binaural fold down to preserve as much of the surround mix as possible. It's not 1:1 and 1:1 is not possible here! (There are ambiguous areas folding down to binaural. Surround really does need speakers and you need to immerse yourself in the speaker array and turn your head to the sides a little here and there. BUT... this at least gives you something of the surround mix to hear.)

The in between channel arrays will downmix with the Atmos system as well as the speaker array allows. A 5.1 array will preserve a lot of the discreteness but obviously the height channels would be folded down to the ground floor, for just one example.

In short, it downmixes as well as possible to what you have to preserve as much of the mix as possible. The mixer can set some downmix rules and audition and tweak that in. Again, this isn't really new like the Atmos brochure would lead one to believe but it is extended from past systems. The binaural stereo bit is new to Atmos. This is all compromised to be clear! But it preserve more of a surround mix than in the past and might lead to a single inventory mix.

A shitbar is gonna shitbar though. You won't even have decent stereo. These are made for crude movie mixes. You get a center speaker for dialog. Everything else is literally ricocheted off your walls and ceiling. Crudeness and lo-fi and not suitable for music IMHO.

Atmos can deliver 7.1.4 1:1 to a 7.1.4 speaker array. This is reference quality. Everything else is winging it and you get what you get! But it's a big step forward and it preserves some of a surround mix for the surround system challenged.

The other direction - upmixing to a larger theater speaker array (with all the surround channel positions you've never even seen before), the Atmos object system is like a vector line drawing when expanding to more speakers. So you hear a smooth motion in a large theater instead of a speaker bank hocket to another speaker bank. This requires the mixer to use this system and dial it in! A straight 7.1.4 mix with no object use would upmix the same as in the past.

Now someone COULD make an Atmos mix that was 9.1.6 and had another 120 object elements and absolutely requires a full theater install Atmos system with all the channels! Most of the music mixes are mixed on a 7.1.4 speaker array. That's the reference system to shoot for if you want to hear the 12 channel music mixes 1:1 as the engineer heard it.

And you know, most music mixes at present are 5.1. And there will be plenty of phoned in Atmos mixes that aren't much more than stereo just to insult anyone who set up a full system. Of course I recommend 7.1.4 but you're not exactly just missing everything if you stall for a while. Take your time and don't compromise on speakers. Perhaps consider getting through the software dance first. Speakers all hooked up but the decoder being elusive is a frustrating experience otherwise!

 

[kfbkfb]

Is it common to spend money/time to adjust the Atmos downmix parameters (seems like an Atmos downmix is for a minority of listeners)?


Kirk Bayne

 

[MidiMagic]

So where are these downmix rules imposed?

I am assuming that a standard player is being used and that no other special equipment is present. How are downmix rules applied to the signals?

- Recorded on the medium (e.g. a separate set of tracks)
- Rules on the medium loaded into the player.
- Rules in the player
- Somewhere else

Does it depend on what player you have?

And I want to know what the soundbar actually does, not your opinion of how well it does it.

 

[SeeMoreDigital]

So where are these downmix rules imposed?

I am assuming that a standard player is being used and that no other special equipment is present. How are downmix rules applied to the signals?

- On the medium
- In the player
- Somewhere else

Does it depend on what player you have?

And I want to know what the soundbar actually does, not your opinion of how well it does it.

A media 'player' has no idea what Atmos (or any other bit-streamed audio format) is. This is the job of the audio decoder...

 

[zeerround]

The only reason I mentioned players was the subject of "discrete 5.1" to stereo was raised. "Discrete 5.1" would not be encoded (other than LPCM), so in that case there is no decoder to do the downmix.

 

[jimfisheye]

There is metadata with the audio in an Atmos file. The receiving decoder uses this + the speaker array available to make its render settings on the fly. The output from the decoder is just 12 channels of audio (or 6 folded down to a 5.1 system or 2 folded down to binaural stereo). That's just normal channels of audio at that point.

The Atmos decoder software reads the metadata to determine what the format is. It knows your speaker array because you told it. (Setup in the computer audio OS or AV receiver controls.)

Soundbars will have an official Atmos decoder just like an AVR or the software on the computer. There's no difference there. Soundbars don't really have proper speakers to put that audio into after and thus the sucking. They decode the encoded Atmos literally the same and by the book. They're customized to expect a stock movie mix that is center dialog, maybe some music pad in front L/R, and occasional folly that goes "zing" in the surrounds. Ricochet a full audio channel off your ceiling and back wall and that starts to sound rather crude. Super effective and efficient for movie soundtracks. Mutilating for music.

 

[DuncanS]

Just reading this makes me think that where I feel the Rear speakers are louder compared to the fronts it is because the mixer set a 7.1.4 bed, I have a 5.0.4 set-up.

So my Rear (in 5.1, but sides in 7.1 parlance) speakers carry both the Side & Rear Surrounds as they are mapped down onto them, whereas if the Rears or Sides were meta encoded as vectors they would be placed as virtual speakers. Is this a valid thought?

 

[zeerround]

Again, “it depends” on the engineer, but without double checking to refresh my memory by default sides are going to get mixed down into the fronts (instead of the way I would do it, which is 50% front 50% rears, so the sound image is consistent with the larger speaker layout).

 

[jimfisheye]

The side vs rear faux pas between 5.1 and 7.1 really rears its ugly head at this point doesn't it! There were actually two versions of 5.1 format. 5.1 (side) and 5.1 (rear). Nobody respected this and it effectively became kind of a depreciated feature. Select media players might, others do it wrong. The rears in 5.1 were meant to be the rears in 7.1. The sides were the addition. The 5.1 (side) format was supposed to be the outlier that translated to the side channels in 7.1.

It means you have to grab the controls sometimes. This is an example where it would suck to do this with an AV receiver instead of a computer!

Anyway, I've been thinking I might start delivering the rear channels in Atmos format as objects to work around this. Not a unique idea - others are already doing just that. 5.1 bed + 6 objects instead of 7.1 bed + 4 objects.

 

[zeerround]

That is just one example of Dolby mix down rules that don’t make sense. Another, from memory, is 9.1.6 to 7.1.4 in the treatment of the front “wide” channels. I guess I came to a similar solution, author in 7.1.4 and use objects for wides. Oh I think the .6 to .4 might be “wrong” as well. Moving channels frontwards vs. mixing so the result is the intended same.

 

[SeeMoreDigital]

That is just one example of Dolby mix down rules that don’t make sense. Another, from memory, is 9.1.6 to 7.1.4 in the treatment of the front “wide” channels...

Out of interest... Where can you find 9.1.6 encoded content on a disc. And what's the audio format?

Is it some Auro 3D encoded stuff?

 

[jimfisheye]

Hardly anyone is giving providence on Atmos mix channel format they used on the album cover at present. We only know from reading about the mix engineers talking about setting up in 7.1.4. Most album covers just state "Atmos" and omit the channel array.

You can gather insight from the dolby reference player. Set to decode to 7.1.4 - if the front and rear height channel pairs are identical the mix was likely 7.1.2, for one example.

Is someone talking about their mixes being done on a 9.1.6 speaker array?
The format supports it. 9.1.6 is considered the full 16 channel reference format. 7.1.4 is the "common" 12 channel reference format and we just happen to know that mix engineers are making their mixes with this array.

If you want to hear what they heard, that's 7.1.4.
If the downmix rules are done correctly and the system is setup correctly, upmixing to larger should preserve that mix and just expand it.

I'm already approaching near field (between mid and near) with 7.1.4 in my mix room! 9.1.6 is just not going to happen. And 7.1.4 is the array that hit right now so... alright! I'll just be a downmixing consumer if someone out there starts releasing stray 9.1.6 mixes. If it becomes all the rage and everyone decides 12 channels is not enough (yeah, right!) I'll have to set up a bigger room!

 

[jimfisheye]

Decoding an Atmos stream with non-Atmos decoder results in a corrupted output missing all object audio. A 7.1.4 mix would have the 4 height channels omitted. Possibly more if more objects were used for mix elements.

It will be a corrupted decode missing audio channels. This is by design to coax you into buying the new decoder. And of course the current hold on releasing the decoder license to 3rd party software media players leads to requiring a new hardware purchase to get access to the music at present. Hence the software dance to acquire the dolby reference player app.

The only software that can fully decode TrueHD+Atmos at present is the dolby reference player. Period. Full stop.

 

[LuvMyQuad]

Decoding an Atmos stream with non-Atmos decoder results in a corrupted output missing all object audio. A 7.1.4 mix would have the 4 height channels omitted. Possibly more if more objects were used for mix elements.

It will be a corrupted decode missing audio channels. This is by design to coax you into buying the new decoder. And of course the current hold on releasing the decoder license to 3rd party software media players leads to requiring a new hardware purchase to get access to the music at present. Hence the software dance to acquire the dolby reference player app.

The only software that can fully decode TrueHD+Atmos at present is the dolby reference player. Period. Full stop.

This is not correct. Nothing is omitted. It just becomes 7.1. The height channels are already embedded in the bed channels. Atmos processing just re locates them from the beds to the heights.