Atmos vs 5.1

[Owen Smith]

In this post you can find a summary of what I have found: https://www.quadraphonicquad.com/fo...tmos-parts-appear-in-stereo.35022/post-741118

Please, if you have any evidences for or against that post, I would like to hear them.

That post matches my understanding, and goes into more detail about what happens when playing back on a 5.1 or 2.0 system vs the optional DD 5.1 substream. I'm dismayed (but I have no evidence either way) you say the decoder has the option to chose the lossy DD 5.1 for playback on a 5.1 system, I'd much prefer if if the True HD 7.1 were always used. Any decoder that knows about Atmos playback rules and downgrades will be capable of playing True HD.

 

[Owen Smith]

It is cheaper in man hours and can sound fine if the Atmos mix is good and the mixer takes the 5.1 output into consideration. It wouldn't be output as lossy.

Dolby Digital is always lossy, in any speaker configuration. If it isn't output as lossy then it isn't the DD that is being played.

 

[Owen Smith]

The "recording of that element" in the metadata would be a difference audio signal. The result of subtraction of one audio signal from another. Precisely the style of relationships and manipulation used in past systems, yes! That's still object audio in the metadata though. @steelydave does a much better job of accuracy than I did but we're not in disagreement.

My point was meant to be that the system keeps actual discrete audio channels throughout the process. Involving lossless phase inversions and mlp mysteries as it may be. I thought I read it the other way around when I read some tech papers a few years ago now. Maybe I read a 'simplified' version? But alright... difference signals in the metadata then from all the object channels. Same end result.

In other words you've completely changed your view of how this works.

And in this new view of how this works there are no "older codecs" that will omit playback of the objects.

 

[himey]

I'm dismayed (but I have no evidence either way) you say the decoder has the option to chose the lossy DD 5.1 for playback on a 5.1 system, I'd much prefer if if the True HD 7.1 were always used.

Not every receiver has TrueHD. It is a separate track for compatibility.

 

[himey]

Dolby Digital is always lossy, in any speaker configuration. If it isn't output as lossy then it isn't the DD that is being played.

You can output a lossless 5.1 file from the main DAW session.

 

[Owen Smith]

Not every receiver has TrueHD. It is a separate track for compatibility.

That's fine, you play this on a year 2000 system you get the Dolby Digital 5.1 track.

What I don't like is that an Atmos decoder, which by definition can decode True HD, appears to be allowed to choose the DD 5.1 instead when playing back on a 5.1 system. That's nuts.

 

[Owen Smith]

You can output a lossless 5.1 file from the main DAW session.

I which case it isn't the Dolby Digital substream. It might or might not be the 5.1 audio that was then encoded to create the DD 5.1 substream, but that's not the same as actually being the DD 5.1. There will be differences between the two due to the DD lossy encoding.

 

[himey]

What I don't like is that an Atmos decoder, which by definition can decode True HD, appears to be allowed to choose the DD 5.1 instead when playing back on a 5.1 system. That's nuts.

Why do you think that? That track will be ignored unless the receiver doesn't do TrueHD.

 

[himey]

I which case it isn't the Dolby Digital substream.

Same 5.1 mix derived from the DAW output. One for compatibility (DD), one for promoting an included 5.1 mix (lossless). The Goat Head Soup had a different mix for the Dolby Digital track I vaguely recall.

 

[GOS]

Same 5.1 mix derived from the DAW output. One for compatibility (DD), one for promoting an included 5.1 mix (lossless). The Goat Head Soup had a different mix for the Dolby Digital track I vaguely recall.

Please, don't be vague. lol

 

[LuvMyQuad]

You guys have restored my idea of how it works.

Consider that if you rip the 7.1 files to FLAC, they can also be played back on a processor that does not do Dolby TrueHD. This would allow those with old processors to get lossless playback in 7.1 (or 5.1 with the processor doing the downmix for 5.1). The processor would need 7.1 capability though.

Edit: I wonder if this is related to why the vast majority of older non Atmos processors were 7.1 capable when the vast majority of titles were released as 5.1, at least for music releases. In fact, I can't recall any 7.1 music releases. I don't buy movies. Are there many with 7.1 audio?

 

[Owen Smith]

Why do you think that? That track will be ignored unless the receiver doesn't do TrueHD.

That's not what @AYanguas said in his post, he said the decoder can choose either the True HD or the DD 5.1.

Edit: I think there may be some confusion between separate DD 5.1 tracks and the DD 5.1 substream that can be embedded in the Atmos True HD track. Either or both could optionally be present on a disc. Not sure why both would ever be though.

 

[Owen Smith]

Consider that if you rip the 7.1 files to FLAC, they can also be played back on a processor that does not do Dolby TrueHD. This would allow those with old processors to get lossless playback in 7.1 (or 5.1 with the processor doing the downmix for 5.1). The processor would need 7.1 capability though.

You could do the downgrade to 5.1 yourself, just add each rear channel to the respective side channel and you'd have a 5.1 FLAC. Your processor would only need 5.1 capability then, which they all had unless we're talking vintage quad gear (and you could downgrade to that too in the file if you want).

 

[AYanguas]

That post matches my understanding, and goes into more detail about what happens when playing back on a 5.1 or 2.0 system vs the optional DD 5.1 substream. I'm dismayed (but I have no evidence either way) you say the decoder has the option to chose the lossy DD 5.1 for playback on a 5.1 system, I'd much prefer if if the True HD 7.1 were always used. Any decoder that knows about Atmos playback rules and downgrades will be capable of playing True HD.

In my summary post I say:

- If the system has only 5.1 speakers, It will decode the Substream 2: 5.1 if available, or the Substream 1: TrueHD 7.1, with the capabilities of the AVR.

This is really a guess of mine. If the AVR has 5.1 speakers will not have Atmos capability either because it works that way or because it is an old AVR without Atmos.

Then the AVR will behave the same way as with an input file TrueHD 7.1 without Atmos. It will play the TrueHD lossless with the kind of "downmix" that is able to play 7.1 in a 5.1 channels.

If the AVR is old and not recognize 7.1, then it would play the 5.1 AC3 lossy substream, if is available in the file. (I think the standards for Bluray enforce that for backwards compatibility).

Again, this is my assumption, logically.

 

[AYanguas]

That's fine, you play this on a year 2000 system you get the Dolby Digital 5.1 track.

What I don't like is that an Atmos decoder, which by definition can decode True HD, appears to be allowed to choose the DD 5.1 instead when playing back on a 5.1 system. That's nuts.

It's logical that if the decoder recognizes TrueHD (either Atmos capable or not), then it will play TrueHD 5.1

The lossy 5.1 would only be played by an old AVR that does not recognize TrueHD.


Here are the tests I did with my Denon 8500, configured for less speakers:

Both tests with the same TrueHD Atmos input:

- 7.1 speakers is the minimum for the AVR to recognize (and decode) the Input Signal Atmos
- 5.1 speakers. Does not recognize Atmos input. Plays TrueHD 7.1 input ---> "downmixed" to TrueHD 5.1 (Didn't have avaialable neither the Sound Option Atmos from the remote)

 

[AYanguas]

That's not what @AYanguas said in his post, he said the decoder can choose either the True HD or the DD 5.1.

Edit: I think there may be some confusion between separate DD 5.1 tracks and the DD 5.1 substream that can be embedded in the Atmos True HD track. Either or both could optionally be present on a disc. Not sure why both would ever be though.

I think TrueHD track may have (or not) an embedded DD+ for retrocompatibility. Perhaps is mandatory to have if for the Blu-Ray standards.

The separate track 5.1 is usually DTS HD-MA

I dont think any Bluray has a separate DD 5.1 track. Only DVD has a separate AC3, along with a DTS, for example.

 

[key_wiz]

While the amount of proper Atmos headphones is going to dwarf the amount of rooms with an Atmos setup, I don't feel like those of us with a room that can support it are an afterthought. In the various interviews I see online with engineers they seem to have a speaker setup for testing and mixing. Steven Wilson for example has said that he will mix stereo on headphones, but uses a speaker setup for Atmos mixing.

Cost and setup are definitely factors for doing an actual Atmos setup. But for the majority of 5.1 or 7.1 setups the upgrade cost isn't what I would consider insurmountable. Atmos doesn't need a crazy speaker investment and most AVRs or Preamps from the last decade or so can support it. Coming in with nothing, I would also say that unless you have constraints you just can't work around you would want to build an Atmos setup.

No doubt there are some like Wilson who prioritize the full Atmos speaker system. But I have to question whether that is true for many/most of the engineers cranking out a lot of the mixes we see streaming. Many are quite weak through a full system.

 

[Owen Smith]

This is really a guess of mine. If the AVR has 5.1 speakers will not have Atmos capability either because it works that way or because it is an old AVR without Atmos.

This is not true for my AVR, I have 5.0 speakers and it allows me to select Atmos, DTS:X and Auro. I think you are making too many assumptions.

 

[Owen Smith]

I think TrueHD track may have (or not) an embedded DD+ for retrocompatibility. Perhaps is mandatory to have if for the Blu-Ray standards.

It's DD not DD+.

 

[AYanguas]

This is not true for my AVR, I have 5.0 speakers and it allows me to select Atmos, DTS:X and Auro. I think you are making too many assumptions.

Nice.
Well, I only can speak with my experience with my Denon.