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

[sjcorne]

Beds presently go up to 7.1.2 configuration.

 

[barfle]

Not sure if this is the correct forum topic --- but here I go... OK, Hive Mind, interestingly I have been sent a advance promo of an album for review that is Atmos. However, the format I received it in is WAVE, 10 channels. So, from my perspective, that would be 5.1.4. But what software if any can play that file and I seriously doubt that sending it out over HDMI to the processor would actually yeild the correct results. Thoughts? Please know that I confirm what is contained in the WAVE file by opening it in Sound Forge, but I do not have a multi-channel analog out from any PC to handle this!

Probably my best bet is to go back to the promoter and ask for an MKV or MP4 - but I thought I would try here first to see if anyone has encountered this, and if they know a solution.

I downloaded a file something like that, with the description that included the word “Atmos.” First, I couldn’t open it with any hardware oe software I own, so I tossed it. Second, as I understand Atmos, a channel-based WAV file is contradictory to tha object-based Atmos spec, so although it may have been intended to include overhead speakers, it was NOT Atmos.

 

[hi-res_edition]

Thanks to various responses and PM's I have received. The comments helped me sort this out, and here is my report.

The 10 Channel WAVE plays in surround only when played via VLC on a Windows 11 PC configured for Atmos. Used HDMI with the default audio as the Processor. Info shows as TrueHD. in VLC. Honestly I was surprised it played it at all. Also, tested via the AppleTV 4K using the VLC app on that device. Interestingly it only played the height channels, on the floor --- nothing else! But, that little app is certainly helpful to play surround files if I want... so thanks for that suggestion to try to play from that device. Finally, I have made a request to the promoter for consumer version of the Atmos files, be it MKV or MP4 and look forward to receiving those as I already enjoyed the 5.1 mix from the WAVE file.

Another side note, for those ripping BD's - I learned in the process that I can play .THD files through VLC. These are track by track rips of the Atmos version found on BD's Unlock the ISO and use DVD Audio Extractor in Direct Stream mode, which will output .thd files in seperate tracks.. I would be curious if others have tried this with success or found issues that I am not yet aware of....

 

[LB-V]

How big is the "bed"? I would assume 5.1? Maybe 7.1? I doubt that it would be only 2.0. Back to the original question what about Atmos played in stereo? Not that I really care it's just that now I'm rather curious.

I understand streaming, Atmos has a bed of 5.1 and BlueRay is 7.1.

Atmos in straight stereo is just a mix down.

 

[AYanguas]

I understand streaming, Atmos has a bed of 5.1 and BlueRay is 7.1.

Atmos in straight stereo is just a mix down.

Atmos 'Bed channels' is not the same as the number of channels that you see in a TrueHD or DD+ file.

Encoding Atmos:

When mixing a Dolby Atmos, you can put individual sounds either on 'Bed channels' or in 'Objects'.

The Atmos 'Bed Channels' are 'fixed' speaker locations of 7.1.2. The usual floor 7.1 and two heights located as Top Middles. The mixer can put sounds on any number of beds, or not. LFE is only 'Bed'.
If you want other location different from the 7.1.2, you need 'Objects'.

The Atmos 'Objects' have additional metadata defining its characteristics: 3D location and other 'size' parameters.

When rendering the final consumer file, for example, under TrueHD (for Blu-rays), up to 4 substreams can be generated:

Substream 1: 7.1 Lossless TrueHD (Downmix to 7.1 of the whole Atmos mix for backwards compatibility)
Substream 2: 5.1 AC3 (Downmix of the whole mix, for backwards compatibility). I think is optional.
Substream 3: 2.0 Stereo (Downmix of the whole mix, for backwards compatibility). I think is optional.
Substream 4: Atmos Metadata. Mandatory. Contains the sounds and metadata descriptions of the individual sounds mixed, either on 'Bed' or on 'Objects'

The final TrueHD file is seen as having 8 channels (7.1) (8 channels, not 8 beds)

If the final consumer file is DD+/JOC (used for streaming), The Dolby Digital+ file is seen as having 6 channels (5.1) (6 channels, not 6 beds).

Decoding Atmos:

If the player sends the file 'bitstream' to the AVR, the player is not decoding anytyhing. (Dolby MAT is a special case, not talking here about it).

The decoder on the AVR, or by software, reads the final custom file TrueHD or DD+ and:

- If it supports Atmos, will understand the Substream 4: Metadata and will do the decoding acording to the speaker configuration.
- If it Does Not Suport Atmos, it will ignore Substream 4 and will play a 'standard' TrueHD (7.1)
- 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.
- If the system has only 2 Speakers, it will decode the Substream 3: 2.0 if available. If not available, the AVR will play as when playing a TrueHD 7.1 file. It will 'downmix' if that is implemented in the AVR

Downmixing Atmos to 5.1:

The downmix done by the render tool to obtain the final consumer file (TrueHD or DD+) may give good results or not, depending on the mix itself. That is what you get when playing a Dolby Atmos file in a 5.1 system.

If the results are not so good, then some mixers like Steven Wilson, do a separate aditional 5.1 mix, specifically tailored to sound good, according to his taste.