Stereo to 5.1 Unwrapping Plug-in for Audition

[JZuck]

Trying to do a quick stereo-5.1 conversion. I know it's not ideal but in a crunch. I was wondering if anyone here had had success with any tools or plug-ins or a workflow that works. There's a free DCP creation tool called DCP-o-matic that does it so there MUST be some open source code out there. Most of the commercial stuff is like $400 which seems excessive. Thanks!

[Rick0725]

I use the ADL pentio 5 Composer vst plugin in an audition multi track session. you will need an iloc for authorization.

Rick

[Charles VW]

The Channel Mixer effect in Audition has a "matrixed stereo to ITU 5.1 preset". Put that on a 5.1 master or bus and feed it a stereo signal and it will populate L/C/R/Ls/Rs.

[JZuck]

Thanks. Almost seems too easy. Does it do it in such a way that separates out the center from and lowers the db of the other channels? Does it put anything in LTE? Thanks!

[SteveG_AudioMasters_ · Accepted solution]

JZuck  wrote

Does it put anything in LTE? Thanks!

There is no LTE but there is an LFE, and no, signal should not be going in it, as it stands for Low Frequency Effects. Like thunder and explosions, etc. Since Audition can't determine program content, then it won't put anything in that channel.

The preset does the following:

L = 100% (0dB) L

R = 100% (0dB) R

C = 70.71% (-3dB) L + 70.71% (-3dB) R

Ls = 70.71% (-3dB) L + inverted 70.71% (-3dB) R

Rs = inverted 70.71% (-3dB) L + 70.71% (-3dB) R

LFE 0%

[JZuck]

Thanks for your help Steve! I guess I've seen algorithms that use bandpass filters to trim the low frequencies off of L & R and another to isolate them for the LFE (sorry for the typo). Similarly, I guess it would be ideal to derive the center channel via the extractor?  I guess that's a lot to ask of the Channel Mixer! Thanks for walking me through it.

Jonathan

[SteveG_AudioMasters_]

JZuck  wrote

I guess I've seen algorithms that use bandpass filters to trim the low frequencies off of L & R and another to isolate them for the LFE (sorry for the typo).

I think that the Wikipedia explanation sums it up quite well:

'The LFE channel content is not the same as the content of a subwoofer-out jack. The LFE channel is used to carry additional bass information in the Dolby Digital program, while the subwoofer output is bass information from up to all six channels that has been selected to be reproduced by the subwoofer via a bass management system.'

What this means is that they shouldn't really be doing that, but you can sort-of understand why they might have...

Technically the center channel is correct when established from a stereo signal if it's just the sum of the two channels - it would be out of balance if either it was at a higher level, or the L and R signals had more difference signal in them (which amounts to exactly the same thing). So no, using the center channel extractor would be wrong initially, but you might well want to reconsider this if you're doing a re-balance.

[JZuck]

Thanks for all your time on this! I guess with the LFE, the implication is that the system doesn't NEED us to send lower tones to the subwoofer, it's already doing that and instead only needs us to send effects?

And I guess I thought the center channel was meant to be primarily dialog. Wrong about that too!

thanks again

[SteveG_AudioMasters_]

JZuck  wrote

Thanks for all your time on this! I guess with the LFE, the implication is that the system doesn't NEED us to send lower tones to the subwoofer, it's already doing that and instead only needs us to send effects?

Originally the idea was that your stereo system had full-range speakers - at least for the L and R channels, so 'normal' bass was only supposed to be reproduced through main speakers. That's why it's designated 5.1 - the .1 is essentially separate. The trouble is that a lot of manufacturers thought that having a sub meant that they could get away with small satellite speakers that couldn't reproduce bass, so against the spec, they started sending it to the sub, even though they shouldn't. It also means that the sound in your system is likely to be unbalanced - the LFE level is generally elevated, and the crossover levels and frequencies will accordingly be completely inappropriate.

And I guess I thought the center channel was meant to be primarily dialog. Wrong about that too!

Not really. If the dialog is all center stage, then it will come from the center speaker - but it will also be present as the sum signal in L and R. If you had only dialog in C  and not in L & R, and did a mixdown to a stereo file, then you'd have to add it back anyway - or nobody would hear it!

You have to bear in mind here that this is a plugin that's spreading stereo over 5 channels, and its options are pretty limited. Yes, if you want to create entirely different 5.1 mixes then it's possible to do things like center channel extraction and pull all the really deep bits out and send them to the .1, but you can't do that within the Amplify window - you'd need to set up an effects chain, or possibly two if you're going to do frequency extraction.

[JZuck]

Interesting. Well if a lot of systems (particularly in people's homes) ARE

relying on the subwoofer for bass that would suggest you SHOULD throw the

low tones there even against spec but NOT do it for distribution to a movie

theater which DCP-o-matic is doing.

On Sun, May 19, 2019 at 2:38 PM SteveG(AudioMasters) <

[Richard M Knight]

The redirection of bass to use the sub to make up for any shortfalls in the main speakers in home systems should be done in the replaying amp and not in the 5.1 soundtrack.