MS recording technical questions

meathman · 25th May 2008

Hi i have just purchased an MS rig and had a few questions.

For SFX collecting/ field recording, I use a sound devices 722 and am using the onboard ms decoder so what i end up with out of the recorder is a stereo decoded L-R file.

My question is , once the file is decoded, is there a way to revert back, and extract say , only the M (cardoid) signal, or rebalance the width without any signal loss? i.e. revert back to the M S signal as fig 8 on one chan and cardoid on the other?

If not, would most people recommend monitoring MS decoded but recording as 2 separate files, to decode during the mix?

Thanks

5flagsaudio · 25th May 2008

Files can be decoded using the right processor. I know Waves Imager and Shuffler programs both allow for M/S input or L/R input. Which can be rematrixed again once your satisfied with whatever processing you've done. However, the simplest thing is simply to record them as M/S instead of matrixed.

meathman · 26th May 2008

So if I do record them as MS, can i reverse the process once recorded (encoded) ?

5flagsaudio · 26th May 2008

Yes, they can. I've done it before using the Waves S1 products. I'm not familiar with the hardware processors that would do the same thing, or any of the other plugs that would do the same thing, but the Waves stuff works if you've got it.
In MS audio L is M+S and R is M-S. I suppose it would be possible for you to build a box to dematrix it for you if you desired.

boojum · 26th May 2008

Voxengo is free. It allows you to go either way and vary the mid-side ratios.

With the 722 you can also record but not decode the MS tracks, leaving them in their native format, but listen to them decoded.

Rumi · 27th May 2008

Maybe I'm misunderstanding the question...

You can always convert L/R to M/S and back, using three channels of a mixer.

As was stated, L is M+S and R is M-S. Put the M signal center, the S signal hard left, and again the S signal hard right, but with polarity (what is often called "Phase") inverted. You can vary the amount of the M to S ratio by changing the level ratios between the M channel and the two S channels.

If you want M/S from L/R, sum L and R for M, and sum L and a polarity inverted R for S. Mix to taste.

There will be level differences of 6 dB in some cases that must be compensated.

In Logic there is a "Helper" app that lets you choose between L/R and M/S. I use it all the time for Mastering etc. (converting to M/S, changing the M/S ratio or processing only M or only S, then converting back to L/R, with 6 dB make up gain).

I would record in M/S and convert to L/R while mixing. There is no loss whatsoever.

Google comes up with lots of information about M/S.

Cheers, René

aracu · 28th May 2008

With the Sound Devices, you can also record to two mono files, monitering as ms without actually processing the files. Not better, just another possibility. Waves Stereo Imager will allow you to process files recorded with two non-ms coincident mics as though they were ms, adjusting the stereo image and/or shuffling.

Matt Biermann · 28th May 2008

Quote:

Originally Posted by René Hatt

Maybe I'm misunderstanding the question...

You can always convert L/R to M/S and back, using three channels of a mixer.

As was stated, L is M+S and R is M-S. Put the M signal center, the S signal hard left, and again the S signal hard right, but with polarity (what is often called "Phase") inverted. You can vary the amount of the M to S ratio by changing the level ratios between the M channel and the two S channels.

If you want M/S from L/R, sum L and R for M, and sum L and a polarity inverted R for S. Mix to taste.

There will be level differences of 6 dB in some cases that must be compensated.

In Logic there is a "Helper" app that lets you choose between L/R and M/S. I use it all the time for Mastering etc. (converting to M/S, changing the M/S ratio or processing only M or only S, then converting back to L/R, with 6 dB make up gain).

I would record in M/S and convert to L/R while mixing. There is no loss whatsoever.

Google comes up with lots of information about M/S.

Cheers, René

+1. Save your money and do it manually, or build your own plugin to do it in Synthedit or something.

wakah · 28th May 2008

It's easy to do it manually in your mixer:
R=M+S
L=M-S
(L+R)/2=M
(L-R)/2=S
if your lazy, you can also use the free voxengo plugin

M/S encoding/decoding is also very interesting for mastering/mixing, try equalising/compressing/... only M or S and listen what happens. It's so easy, yet so powerfull at the same time :p

25th May 2008	#1
meathman Gear nut Joined: Feb 2007 Posts: 116 Thread Starter	MS recording technical questions Hi i have just purchased an MS rig and had a few questions. For SFX collecting/ field recording, I use a sound devices 722 and am using the onboard ms decoder so what i end up with out of the recorder is a stereo decoded L-R file. My question is , once the file is decoded, is there a way to revert back, and extract say , only the M (cardoid) signal, or rebalance the width without any signal loss? i.e. revert back to the M S signal as fig 8 on one chan and cardoid on the other? If not, would most people recommend monitoring MS decoded but recording as 2 separate files, to decode during the mix? Thanks

26th May 2008	#5
boojum Lives for gear Joined: May 2007 Location: Astoria, OR, US&A Posts: 2,308 1 Review written	Voxengo is free. It allows you to go either way and vary the mid-side ratios. With the 722 you can also record but not decode the MS tracks, leaving them in their native format, but listen to them decoded. __________________ Nov schmoz ka pop. Last edited by boojum; 26th May 2008 at 02:50 AM.. Reason: shpeling

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25th May 2008	#2
5flagsaudio Gear nut Joined: Mar 2008 Location: Northwest Florida Posts: 81	Files can be decoded using the right processor. I know Waves Imager and Shuffler programs both allow for M/S input or L/R input. Which can be rematrixed again once your satisfied with whatever processing you've done. However, the simplest thing is simply to record them as M/S instead of matrixed.

27th May 2008	#6
Rumi Lives for gear Joined: Oct 2003 Location: Zurich, Switzerland Posts: 564	Maybe I'm misunderstanding the question... You can always convert L/R to M/S and back, using three channels of a mixer. As was stated, L is M+S and R is M-S. Put the M signal center, the S signal hard left, and again the S signal hard right, but with polarity (what is often called "Phase") inverted. You can vary the amount of the M to S ratio by changing the level ratios between the M channel and the two S channels. If you want M/S from L/R, sum L and R for M, and sum L and a polarity inverted R for S. Mix to taste. There will be level differences of 6 dB in some cases that must be compensated. In Logic there is a "Helper" app that lets you choose between L/R and M/S. I use it all the time for Mastering etc. (converting to M/S, changing the M/S ratio or processing only M or only S, then converting back to L/R, with 6 dB make up gain). I would record in M/S and convert to L/R while mixing. There is no loss whatsoever. Google comes up with lots of information about M/S. Cheers, René

28th May 2008	#7
aracu Lives for gear Joined: Jul 2006 Posts: 850	With the Sound Devices, you can also record to two mono files, monitering as ms without actually processing the files. Not better, just another possibility. Waves Stereo Imager will allow you to process files recorded with two non-ms coincident mics as though they were ms, adjusting the stereo image and/or shuffling.

28th May 2008	#9
wakah Gear interested Joined: Jun 2007 Location: belgium/brussels Posts: 14	It's easy to do it manually in your mixer: R=M+S L=M-S (L+R)/2=M (L-R)/2=S if your lazy, you can also use the free voxengo plugin M/S encoding/decoding is also very interesting for mastering/mixing, try equalising/compressing/... only M or S and listen what happens. It's so easy, yet so powerfull at the same time :p