Atmos and TrueHD 7.1 playback on 5.1 systems - Tests, Results, questions, experiences

[castironshore]

Forgive me if this is a stupid question but what happens to the discrete sounds from the ceiling and side speakers when downmixed to 5.1? Do they go to the back speakers as discrete channels (for example the side L speaker going to the rear L speaker discretely and the side R speaker going to the rear R speaker discretely) or does the sound go to both of the back speakers at the same time (non-discretely)?

 

[ar surround]

Forgive me if this is a stupid question but what happens to the discrete sounds from the ceiling and side speakers when downmixed to 5.1? Do they go to the back speakers as discrete channels (for example the side L speaker going to the rear L speaker discretely and the side R speaker going to the rear R speaker discretely) or does the sound go to both of the back speakers at the same time (non-discretely)?

Stupid question? Probably one of the smartest questions in regard to how Atmos renders when downmixed.

 

[castironshore]

Stupid question? Probably one of the smartest questions in regard to how Atmos renders when downmixed.

Thanks. Any ideas?

 

[himey]

Forgive me if this is a stupid question but what happens to the discrete sounds from the ceiling and side speakers when downmixed to 5.1? Do they go to the back speakers as discrete channels (for example the side L speaker going to the rear L speaker discretely and the side R speaker going to the rear R speaker discretely) or does the sound go to both of the back speakers at the same time (non-discretely)?

I found this earlier this morning which may help you.

 

[castironshore]

I found this earlier this morning which may help you.

Thanks for that, but the discussion is completely over my head. Can someone explain it to me like they would to a child?

 

[himey]

Thanks for that, but the discussion is completely over my head. Can someone explain it to me like they would to a child?

To some extent, the mixing tools and the mix engineer has control over this. So the real answer to the original question is, it depends.

The objects get moved depending on the speaker layout. If you don't have top channels, nothing gets moved to the top channels.

 

[castironshore]

To some extent, the mixing tools and the mix engineer has control over this. So the real answer to the original question is, it depends.

The objects get moved depending on the speaker layout. If you don't have top channels, nothing gets moved to the top channels.

So if there's Atmos sound coming out of the top channels, those end up not coming out anywhere on a 5.1?

 

[himey]

So if there's Atmos sound coming out of the top channels, those end up not coming out anywhere on a 5.1?

No. They start and stay in the 5.1.

 

[castironshore]

No. They start and stay in the 5.1.

That’s good. Which speaker does the ceiling come out of when it’s played in 5.1?

 

[Kal Rubinson]

That’s good. Which speaker does the ceiling come out of when it’s played in 5.1?

Good question. In my 5.1.4 system, "Top Side Right" comes out of both FR and SR bed channels, iirc. If I get a chance, I can the 9.1.6 test signals through my system and take notes.

 

[himey]

That’s good. Which speaker does the ceiling come out of when it’s played in 5.1?

Again, it will depend on how it was mixed.

You are looking at the process backwards. The ceiling speakers can be in multiple configurations. If you are not using ceiling speakers, the 5.1 stays in place because the metadata is ignored. The ceiling speakers are never engaged, so they stay right in the 5.1. Depending on the setup with ceiling speakers, 5.1.2, 7.1.2, 5.1.4, 7.1.4, 9.1.6, the last number being how many ceiling speakers are used, will determine where the sounds will be placed.

 

[sjcorne]

That’s good. Which speaker does the ceiling come out of when it’s played in 5.1?

If you're using an older 5.1 AVR with no Atmos decoding - the content meant for the front heights will play in the front speakers (though if anything is centered in the front heights, it goes to the discrete center speaker instead), while the sides, rears, and rear heights will be combined into a single pair of rear speakers. No information is lost, but the results can sound kind of weird or back-heavy depending on how much the sides are used (for example, there are a handful of Atmos mixes that place lead vocal in those side speakers).

 

[castironshore]

Thanks for all the replies. I have an Oppo BDP 95, which I believe is from 2012, with the most recent firmware update in 2014. Since it doesn't have any Atmos decoding, it sounds like Atmos mixes will not be as discrete as if the music was mixed specifically for 5.1.

 

[sjcorne]

...it sounds like Atmos mixes will not be as discrete as if the music was mixed specifically for 5.1.

Some titles translate really well, others less so. I think it's worth exploring in any case, as there's so much music available in this format.

 

[himey]

Thanks for all the replies. I have an Oppo BDP 95, which I believe is from 2012, with the most recent firmware update in 2014. Since it doesn't have any Atmos decoding, it sounds like Atmos mixes will not be as discrete as if the music was mixed specifically for 5.1.

There are discrete Atmos mixes for sure, even without decoding. There are non-discrete 5.1 mixes. Mix is king not the format.

 

[AYanguas]

To shed some light on this matter I have been doing the following tests:

Test file: Dolby Atmos speakers test 9.1.6 from Dolby Test Blu-ray

The test file has a TrueHD Atmos track that sends individual noise to each 9.1.6 speaker. I don’t know if the Atmos mix has been done using bed channels or objects, or both, because I think to remember that there are only two bed channels for the Atmos Heights.​

AVR: Denon AVC-X8500H

Using each of the following configurations:​

​

9.1.4 (7.1.4 + Wides)​

​

7.1.6 (7.1 + Top Fronts, Top Middles, Top Rears)​

​

7.1.4 (7.1 + Top Fronts, Top Rears)​

​

7.1 (LCR + Surrounds + Surround Backs)​

​

5.1 (LCR + Surrounds)​

Testing:

I was curious to know if at any time the rendering of the Atmos test file makes any sound image using several speakers. To be sure, I have used my visual VUMeters, with enough volume level, that show me exactly if any speaker is fired.​

TEST RESULTS:

All tests results have been always that only a single speaker is fired in all cases, except the Top Middles when there is only 4 Height Speakers.​

​

There was No image (as I was expecting) combining fronts and surrounds for Wides, or Tops.​

AVR Config: 9.1.4

Top Middles => Both Top Front and Top Rear​

AVR Config: 7.1.6

Wides => Fronts​

AVR Config: 7.1.4

Top Middles => Both Top Front and Top Rear​

Wides => Fronts​

AVR Config: 7.1

Wides => Fronts​

​

Top Fronts => Fronts​

​

Top Middles => Surrounds​

​

Top Rears => Surround Backs​

AVR Config: 5.1

Wides => Fronts​

​

Surround Backs => Surrounds​

​

Top Fronts => Fronts​

​

Top Middles => Surrounds​

​

Top Rears => Surrounds​

As seen in pictures below, I have made sure that the AVR Sound Option is setup to see a Dolby Atmos input signal.
That was obvious when the speaker config has Height Speakers but was also possible for 7.1 (without heights).
It was not available for 5.1

 

[ar surround]

Thanks. Any ideas?

Some titles translate really well, others less so. I think it's worth exploring in any case, as there's so much music available in this format.

When I accidentally screwed up the settings on my Oppo 205 and was only getting 7.1 instead of Atmos, it was quite apparent that the 'sense of space' had been significantly compromised. So from simply an aural rather than analytical perspective, things simply do not sound as satisfying when they are downmixed rather than rendered as intended in the Atmos mix.

 

[Sal1950]

So from simply an aural rather than analytical perspective, things simply do not sound as satisfying when they are downmixed rather than rendered as intended in the Atmos mix.

I think we've become spoiled.
It's like listening in surround all the time and then playing a 2ch.

 

[soesbeout]

So about 99 percent of this stuff is way over my head but anyway I downloaded the test tones put the folder into the video file of my pc and see if they stream over my home network with my Oppo 93 useing VLC.

 

[LB-V]

Yes.
Atmos in TrueHD is 7.1 (8 channels).
But it use to have also an inner layer in 5.1 (6 channels). You can 'see' it when you load a TrueHD Atmos track on MKVToolNix and get two audio tracks 7.1 (8 channels) and 5.1 (6 channels).
When played on 5.1 system, the AVR could play just that inner 5.1 layer or mix/downmix the sides and rears if the 5.1 layer is not implemented in the file.

Atmos in DD+ is 5.1

Appreciate the clarification.