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

[himey]

I thought there was an option to output either Bitstream or PCM? If that’s true then the player must decode although that would be limited to 7.1 as HDMI 2.0 is limited to 8 channels I believe.

EDIT: That would be an Atmos downmix on an Atmos certified BD player I would think. That is, output channels would follow results here.

The downmix of Atmos is built in the True HD specs.

Selecting pcm will get you a maximum of 7.1 over hdmi or analog.

Selecting bitstream, and outputting over hdmi, will get you Atmos if you have a compatible Atmos processor, and 7.1 max, if the receiver does True HD and not Atmos.

 

[himey]

How an Atmos processor handles Atmos music, downmixed to 5.1 (or 7.1), vs a Dolby TrueHD processor, is an interesting comparison.

On paper it should be the same and the 3D speakers (Atmos) metadata are completely ignored?

 

[HomerJAU]

I think all BD players will have a TrueHD decoder, as part of the BD spec.

 

[HomerJAU]

How an Atmos processor handles Atmos music, downmixed to 5.1 (or 7.1), vs a Dolby TrueHD processor, is an interesting comparison.

Yanguas has tests that would show that. It looks like his Onkyo AVR was non Atmos but had TrueHD decoding. Hopefully he can confirm this.

 

[HomerJAU]

On paper it should be the same and the 3D speakers (Atmos) metadata are completely ignored?

That sound right. We’d need to find a test Atmos track with obvious object data to test. The test files here may Not contain objects, although the Tops may all in fact be encoded as objects with fixed speaker positions.

 

[ar surround]

How did you create the 7.1 FLAC? So far this thread has only tested Dolby Atmos downmixing as output from a Dolby Atmos or TrueHD decoder.

I extracted the 7.1 FLAC files from a MakeMKV backup using DVD AudioExtractor. It is listed as 6 channel TrueHD in the list, but extracts as 8 channel 7.1. The 7.1 channels are shown in Audacity just fine. Then I used Audacity to export the FLAC as 24bit WAV files. I will fool with this some more, but not until tomorrow.

 

[himey]

That sound right. We’d need to find a test Atmos track with obvious object data to test. The test files here may Not contain objects, although the Tops may all in fact be encoded as objects with fixed speaker positions.

You just read my mind, haha.

I didn't even know there was such a format. Sometimes I think I get further out of the loop every day.

This post made me wonder exactly how these files came about considering the 9.1.6 test file.

 

[HomerJAU]

This post made me wonder exactly how these files came about considering the 9.1.6 test file.

These were all created from an official Dolby Atmos Demo disc I purchased online. I trimmed each chapter as the tests were originally 1 minute per channel. Now 10 sec per channel.

 

[HomerJAU]

If anyone with MMH wants to try this it would be good to get the result.

Use the Extract MKV to Audio tool, set Output to FLAC. Select all the test MKVs and Convert to FLAC.

Now playback each FLAC and report what channels playback.

MMH converts the Atmos TrueHD 7.1 Core to FLAC 7.1.

Id do this but I’m busy on my bathroom reno for a couple of days.

 

[himey]

These were all created from an official Dolby Atmos Demo disc I purchased online. I trimmed each chapter as the tests were originally 1 minute per channel. Now 10 sec per channel.

Their files not yours. I thought all the processing was done actively while listening, depending on the speaker configuration?

 

[ar surround]

How did you create the 7.1 FLAC? So far this thread has only tested Dolby Atmos downmixing as output from a Dolby Atmos or TrueHD decoder.

I extracted the 7.1 FLAC files from a MakeMKV backup using DVD AudioExtractor. It is listed as 6 channel TrueHD in the DVD AudioExtractor list, but extracts as 8 channel 7.1. Then I used Audacity to export the FLAC as 24bit WAV files. I will fool with trying to get the Oppo to play a proper 5.1 downmix of this stream, but not until tomorrow.

In the meantime, here is the scan of the Audacity WAV stream. The rear channels are definitely different than the surrounds, both visually and aurally.

 

[HomerJAU]

Their files not yours.

Their Atmos encoded disc.

I thought all the processing was done actively while listening, depending on the speaker configuration?

When played back with decoding on an AVR, yes that’s my understanding.

 

[harync]

I'm very interested in trying out these files, but I can't get them to play properly with an MKV wrapper. My Sony X800m2 can't read the ATMOS metadata when it's in an MKV container, and my LG OLED won't even play MKV at all. Is there anyway to provide the 5.1.4 file in an m2ts or mp4 format. That way I can compare the speaker mapping on my Atmos system to my non-atmos system.

 

[HomerJAU]

Is there anyway to provide the 5.1.4 file in an m2ts or mp4 format.

I can create mp4 files and you can try those. I’ll do that within 24hrs and post here when ready.

 

[HomerJAU]

MP4 versions of all channel test files uploaded. Same link as in first post.

 

[bracelis]

MP4 versions of all channel test files uploaded. Same link as in first post.

I believe most players will not recognize a TrueHD codec in a MP4 container -- you will need to use mt2s.
Or use the MP4 which contains Dolby Digital+ if it's available.

 

[bracelis]

How an Atmos processor handles Atmos music, downmixed to 5.1 (or 7.1), vs a Dolby TrueHD processor, is an interesting comparison.

On paper it should be the same and the 3D speakers (Atmos) metadata are completely ignored?

With a Denon/Marantz Atmos receiver/processor, you can test this:
Configure your speakers to 5.1 (i.e. no height speakers), and bitstream the TrueHD/Atmos test file, and listen and compare these two sound modes (use the "Sound Mode" buttons on the remote):
(1) Dolby TrueHD (this should behave the same way as a non-Atmos TrueHD receiver)
(2) Atmos/Surround

Edit / Correction:
I tried it -- if the speaker configuration doesn't have any height channels (on the Atmos-capable receiver), then the receiver will use TrueHD decoding, not Atmos decoding. In other words, it will behave the same way as a non-Atmos TrueHD receiver.

PS:
I compared "Here Comes The Sun" DTS-HD 5.1 vs Atmos (with TrueHD decoding and without height channels), and I could not notice any difference.

 

[harync]

I believe most players will not recognize a TrueHD codec in a MP4 container -- you will need to use mt2s.
Or use the MP4 which contains Dolby Digital+ if it's available.

Bracelis is correct. Thanks for trying, but unfortunately the mp4 files contain no sound and report as stereo. Here are examples of a DD+ MP4 encoded files that I found on the web that work properly:

https://www.heimkino-atmos.de/.cm4all/uproc.php/0/Trailer/Dolby Atmos/dolby-test-tones_5_1_2.mp4
https://www.heimkino-atmos.de/.cm4all/uproc.php/0/Trailer/Dolby Atmos/dolby-test-tones_5_1_4.mp4
https://www.heimkino-atmos.de/.cm4all/mediadb/Trailer/Dolby Atmos/dolby-test-tones_7_1_2.mp4
https://www.heimkino-atmos.de/.cm4all/mediadb/Trailer/Dolby Atmos/dolby-test-tones_7_1_4.mp4
m2ts would be the best way to properly test TrueHD with Atmos, but I understand the file size constraints.

 

[~dave~~wave~]

Bracelis is correct. Thanks for trying, but unfortunately the mp4 files contain no sound and report as stereo. Here are examples of a DD+ MP4 encoded files that I found on the web that work properly:

Thanks, these work for me on the Sony X800.

 

[harync]

Here are examples of a DD+ MP4 encoded files that I found on the web that work properly:
https://www.heimkino-atmos.de/.cm4all/uproc.php/0/Trailer/Dolby Atmos/dolby-test-tones_5_1_2.mp4https://www.heimkino-atmos.de/.cm4all/uproc.php/0/Trailer/Dolby Atmos/dolby-test-tones_5_1_4.mp4https://www.heimkino-atmos.de/.cm4all/mediadb/Trailer/Dolby Atmos/dolby-test-tones_7_1_2.mp4https://www.heimkino-atmos.de/.cm4all/mediadb/Trailer/Dolby Atmos/dolby-test-tones_7_1_4.mp4

Using the files above, I can report the following results in an Atmos system and a non-Atmos System:

Atmos System is a Sony UBP-X800m2 into a Pioneer VSX-LX503 with 5.2.4 speakers:
5.1.2 -> LF, Center, RF, LS, RS, LFE all map correctly.
Left Height places in LF and LR height, Right Height places in RF and RR height
5.1.4-> All sounds map exactly where they are supposed to
7.1.2 -> All sounds map exactly where they are supposed to, except LR maps to LS and RR maps to RS (as they should). Left Height maps to both LF and LR Height. Right Height maps to both RF and LF height
7.1.4 -> All sounds map exactly where they are supposed to, except LR maps to LS and RR maps to RS (as they should).

Non-Atmos System is a Oppo BDP-93 into a Denon AVR-3312CE with 5.1:
5.1.2 -> LF, Center, RF, LFE all map correctly.
RS has a little bit of bleed through to LS and vice versa
Left Height places in LS only, Right Height places in RS only
5.1.4-> LF, Center, RF, LFE all map correctly.
RS has a little bit of bleed through to LS and vice versa
LF Height places in LF only, RF Height places in RF only
LR Height places in LS only, RR Height places in RS only
7.1.2 -> All sounds map exactly where they are supposed to, except LR maps to LS and RR maps to RS (as they should)
Left Height places in LS only, Right Height places in RS only
7.1.4 -> All sounds map exactly where they are supposed to, except LR maps to LS and RR maps to RS (as they should)
LF Height places in LF only, RF Height places in RF only
LR Height places in LS only, RR Height places in RS only

As I was carrying out this exercise, I realized why an Atmos signal on a 5.1 system will always be lacking: Since Atmos is an object based system, a non-atmos system is going to make errors about placing signals. For example, based on the above results, an object that is supposed to be in both the LF height and LR height in a x.1.4 system (or Left height in x.1.2 system), will only play in the Left surround.

I think the example set by the Abbey Road BD is the best case: simultaneous release of Atmos and properly mixed 5.1.