LT+RT to surround, how?

[tormento]

The title tells it all.

I have found some old BD with LT+RT track, i.e. Dolby Surround.

Is there any way to recover the original surround format?

[SeeMoreDigital]

So.... Is it this? (https://en.wikipedia.org/wiki/Dolby_Pro_Logic#Dolby_Surround_(2014))

[tormento]

Is it this?
Nope, it's some version of Pro Logic, II I think. I need to invert the procedure.

[junh1024]

Not possible to completely reverse the procedure since downmixing loses a lot of information. Please use any surround decoder or upmixer.

[tormento]

Not possible to completely reverse the procedure since downmixing loses a lot of information. Please use any surround decoder or upmixer.
I know that Surcode had a piece of software that allows to recreate the mono wavs from the LT+RT audio.

I'd just like to do the same thing, with freeware software possibily, as Surcode has closed long time ago.

[tebasuna51]

Try with Foobar2000 and the foo_dsp_fsurround.dll (https://hydrogenaud.io/index.php?topic=52235.0) plugin.

[tormento]

Try with Foobar2000 and the foo_dsp_fsurround.dll (https://hydrogenaud.io/index.php?topic=52235.0) plugin.
Can it output to separate mono wav? I never used foobar.

[junh1024]

Can it output to separate mono wav? I never used foobar.

No need, encoding software like eac3to or Totalcode studio already accept 6ch wav.

BTW, if you play using software like PowerDVD, that can upmix 2ch to surround.

Ac3filter's expand stereo, and windows speaker fill should also do basic dematrixing.

Keep in mind you will never completely recover the original: https://i.imgur.com/0o7Rflf.png

[tebasuna51]

Keep in mind you will never completely recover the original

Of course if LT+RT was created with a standard downmix (LT mix of FL + SL, RT mix of FR + SR) it is not possible extract the 4 channels.

But with DplII downmix we can obtain a good aproach

[tebasuna51]

Can it output to separate mono wav? I never used foobar.

It is possible but better try before with wav 5.1.

Foobar method I use, ask if you need more info:

[SeeMoreDigital]

But with DplII downmix we can obtain a good aproach
Have I missed (another) meeting... Where does one find this?

[tormento]

Foobar method I use, ask if you need more info:
You are always so kind!

I think we have both different Foobar and different DSP:

https://i1.lensdump.com/i/tB488K.pnghttps://i2.lensdump.com/i/tB4AQZ.png

Where can I find your FreeSurround package?

[tebasuna51]

Not always the new are better.

But you can try the new one (never redirect bass to LFE please!, the AVR's make that to subwofer automatically and include filters can destroy the sound).

[tebasuna51]

Have I missed (another) meeting... Where does one find this?

I'm not sure what you ask.

More info in 2007 discussion in https://hydrogenaud.io/index.php?topic=52235.msg471734#msg471734
and precedents in 2003 https://forum.doom9.org/showthread.php?p=347432#post347432

[tormento]

But you can try the new one (never redirect bass to LFE please!
I trust your capabilities in audio much more than mine.

When you have time, would you please do some trials with newer plugin version?

Can you please also explain me the Center Image value and Rear Phase Reconstruction options?

[tormento]

Well, it seems that something is wrong with channels.

I used your configuration and:

https://i3.lensdump.com/i/tBbtwM.jpg

[tebasuna51]

Well, it seems that something is wrong with channels.

Wrong is your audio editor, the channels are correct in this order: L,R,C,LFE,SL,SR and not L,C,R,Ls,Rs,LFE

EDIT: verified with your source, the wav output is correct
Of course we can't know if dplII mix method was Dolby compliant
The center channel seems too loud, maybe you can use a Center Image less than 1

[tebasuna51]

When you have time, would you please do some trials with newer plugin version?
With defaults seems the same than old version using Besweet compatibility and mix coeficients 0.8145, 0.5744 (defaults).
The output over a dplII created by eac3to or BeHappy/MeGUI have a little worse channel separation and the SR channel inverted.

Can you please also explain me the Center Image value and Rear Phase Reconstruction options?

Center Image: 0 -> Center channel empty, 1 -> All common values in L and R are extracted to Center channel (recommended)

Rear Phase Reconstruction: is a topic with many opinions, read https://forum.doom9.org/showthread.php?p=347432#post347432 and https://forum.doom9.org/showthread.php?p=837667#post837667

My opinion is:
I make many test using a directshow dplII decoder from PowerDVD and, if that decoder is correct (Dolby compliant), the better downmix method to recover the original channels is:

LT = L + 0.707 C + 0.866 SL + 0.5 SR
RT = R + 0.707 C - 0.5 SL - 0.866 SR
Method used in eac3to, BeHappy and MeGUI.

The BeSweet method is:
LT = L + 0.707 C - 0.866 SL - 0.5 SR
RT = R + 0.707 C + 0.5 SL + 0.866 SR
But the PowerDVD dplII decoder invert now the SR channel
Other coeficients make worse channel separation.