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Old 2nd April 2021, 12:13   #1  |  Link
tebasuna51's Avatar
Join Date: Feb 2005
Location: Spain
Posts: 6,268
3D audio, not only Atmos

I'm interested in 3D audio and I buy a cheap receiver Denon AVR-X1500 and I have the speakers, conexions and config like attached 3D_Front_Dolby.png

With that I can play without problems Atmos (TrueHD or EAC3) or DTS:X from commercial sources and also free ones created in EAC3 Atmos.

But encode to EAC3-Atmos is not easy like junh1024 say here

Also junh1024 send me a free sample .m4a than can be played 3D with my Denon but in a not easy way. Here I want to explain how.

The 7.1 m4a was created with qaac using the 7.1ch front (--chanmask 255) different from the standard 7.1ch rear

MediaInfo inform like:
Channel layout: C L R Ls Rs Lw Rw LFE

Remember the name of channels used by MediaInfo, is equivalent to M$ WAV channels:
Lw and Rw (Left/Right Front Wide) don't have a exact WAV correspondence but maybe can be FLC and FRC (Front Left/Right Center) like the channel mask 255 is.

These last 2 channels must be played by the Front Dolby Left/Right speakers, like a M$ WAV channels:
FL FR FC LFE BL BR TFL TFR (Top Front Left/Right)

To obtain that I need to deceive my Denon AVR-X1500 config it like I have connected Surround Back speakers (instead Dolby) and send the 7.1 PCM like a standard 7.1 FL FR FC LFE BL BR SL SR.

Now I have other problem, my mpc-hc player (the LAV filters) decode the AAC C L R Ls Rs Lw Rw LFE in a wrong order: Lw Rw C LFE Ls Lr L R then I need make a remap like show in 3D_aac remap.png

I attached a little channel test for check 5.1.2 audio systems

My Denon can be configured to have conected to last speakers “Front Height” or “Top Front” (maybe the logical selection) but I can't obtain the correct output even with different remaps in mpc-hc.
Attached Images
Attached Files
File Type: 7z 3D_test_5.1.2.aac.7z (119.2 KB, 18 views)
BeHappy, AviSynth audio transcoder.
tebasuna51 is offline   Reply With Quote
Old 8th April 2021, 07:04   #2  |  Link
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Posts: 37
So to summarize, using extended AAC channels for 51 compatibility but 3D is prolly not gonna work. A basic outline for 3D is this:

1- set your AVR to 71b
2- mix in 71, BUT treat SL SR as BL BR, and treat BL BR as HL HR. Maybe best to mix in 51 + have a separate height bus you can mute & solo.
3- append like, _512sh to your file for clarity

This should work, but might sound horrible when downmixed to 51.
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