Mid/Side Mux/Demux

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gilzad
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Joined: Wed Dec 19, 2012 6:46 am

Mid/Side Mux/Demux

Post by gilzad » Tue Jan 15, 2013 8:09 am

This one is a bit more complicated. That's two DSPs for Mid/Side-processing. Mostly good for mastering.

(Right-Click to save)
Mid/Side Multiplexer and Demultiplexer in action
Mid/Side Multiplexer (Sunsynth module)
Mid/Side Demultiplexer (Sunsynth module)
Demo-file providing mid-sound behind 'TakeLeft' and side-sound behind 'TakeRight'

Background
We've learned how we can have a more accurate control on the sound by treating its frequeny bands separately instead of manipulating the total sum.
Like an EQ can make some sound clearer by adding highs and mids. Or a Highpass-filter can cut unwanted rumbling frequencies. Or a multiband compressor can gain much more loudness by compressing separate bands at once.
One more thing that can be done, is to treat middle and side-information on stereo signals separately. Yes, this is actually possible. As a musician you can decide how the mono-part of your music shall be processed and how the stereo-part shall be processed. I'm not talking about simple panning here. It's about splitting your music into mono and a 100% widened image, treating these two parts separately using any DSP and bringing the mono & widened image together again, so you get back to the stereo sound with its middle and side information being manipulated the way you like.


What is it good for?
I'd say mastering mostly. But it can also be used to design your music or to remove single parts from a stereo image as good as you can.
I have to admit that I never did any Mid/Side-processing myself though. So my knowledge might be limited here. But I could imagine how much more powerful we can use such a thing in sunvox than in any other prepared DSP that encapsulates the Mid/Side-separation along with an integrated EQ or exciter (e.g. Renoise) or other filters. However keeping the Mid/Side mux and demux open for any task, will make things a bit more scientific, thus complicated.
With mid/side-processing:

You can compress the mono-part of your song and leave the stereo sounds uncompressed. Or have them compressed differently. That's what they do in mid/side-processing most of the time.
You can add bass to the mono-part and have the same frequencies completely cut out of the stereo part.
You can widen your stereo image without worrying about loosing center signals on mono playback.
In Sunvox you can apply any DSP to either the mono or the stereo part or both.

The example file
..is not so exciting here. It just shows the multiplexer and demultiplexer from the inside and proves that they are working. To check that, simply pan the sound on the input-dsp to left and right. The chosen loop is an excerpt from The Beatles' "Hey Jude". Beatles-recordings are perfect for testing stereo images as they used to have their instruments hard-panned to left and right.

What is happening?
In the multiplexer
In one step the stereo signal is just being turned into mono and the result is just panned to left. So the left channel of the multiplexer always delivers the middle/center/mono information.
In a second step one of the two available stereo channels (left) is being inverted and mixed together with the other channel. This way anything that is equally available on the left and on the right channel, will cancel out itself. Because after we have inverted the left channel, any center information will become the opposite of itself on the untouched right channel.The result of this is panned to right. So this is the side-information being provided by the right channel of our multiplexer.

Not confused yet? Here's the demultiplexer
The demultiplexer naturally expects the middle/center/mono information on its left input and the side information on its right input.
Now, in one step the mid and side channels are just being mixed together. In this case any sound that is the opposite of the left channel will cancel out the left channel out of the center. What remains is the right track. Now we only need the left track.
In a second step all the side-information is being inverted and mixed to the middle-information again. Now there is no opposite of the left channel anymore, it's inverted, thus exactly the same. But the right channel in the middle-track will be the opposite of the itself in the side-channel. So mixing side and middle together, will bring us the left channel. These two 'decoded' channels are panned to their correct positions again and will represent the natural output of the demultiplexer.
So the output of the demultiplexer will be exactly the input of the multiplexer. Right, we have done so many things to the sound and ended up getting the same sound again. What a waste! ;) No, it's not, hang on.

The Sunsynth modules
For mid/side-processing you'll need a DSP (mux) that splits the sound into mid/side-information and another DSP that decodes this mid/side-info to plain stereo again. Anything that you do in between of these both DSPs is the actual processing. To be able to do this, we'll need to access the left and right output of our multiplexer separately. This demo-file shows how to get there. Simply chain anything you like behind the 'TakeLeft' and/or the 'TakeRight' DSPs.

Like I mentioned, I haven't done any mid/side processing myself, so I'll be happy to see any of you guys finding some use for the mux and demux.

Best,

gilzad

Oliv
Posts: 20
Joined: Wed Oct 31, 2012 4:30 am

Re: Mid/Side Mux/Demux

Post by Oliv » Tue Jan 15, 2013 8:48 pm

Just tested it on an old song in combination with two iteration of your Exciter (accentuating the Bass range on the Mids and the High End on the Sides, respectively).

Some very interesting possibilities. Well done.

That's very nice of you to give us the tools to polish our mixes without having to resort to another application. :)

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samrai katt kovboy
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Re: Mid/Side Mux/Demux

Post by samrai katt kovboy » Tue Jan 15, 2013 10:20 pm

Ahhh
Mid side processing is quite useful and started to use it pretty recently. You just have be a little careful as it can make your mix sound pretty weird in mono, so it's a good idea to switch inbeetwen mono and stereo.
But it's really cool that Mr gilzad made it for sunvox.
As it can really open up sounds.
I like to use it to fatten up bass. Keep the lower frequencies in mono and just widen the upper top frequencies to the sides.

Mr Gilzad
Thank you soooo much for the modules you been doing for us the last month.
Where do we send the champagne...

Easy blue babies floating on top
SOOOOOOOOOOOOOOO MANY CIRCLES

gilzad
Posts: 92
Joined: Wed Dec 19, 2012 6:46 am

Re: Mid/Side Mux/Demux

Post by gilzad » Wed Jan 16, 2013 4:51 am

Thanks guys!
I'm glad you are more aware of m/s-processing than me. I wasn't sure anyone would find this interesting.

@Oliv: Oh, the Exciter..I have to update it to support output volumes and an LQ-version. Hey, I made you post once more! :D
@samrai katt kovboy: We should drink that champagne together! I'll pass out first though. Can I have coffee instead? ;)

On a sidenote: I really like to get to know you people as musicians. Maybe we can add a soundcloud-link or something to our signatures? Only if you want to, of course.

*is going to edit his signature*

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samrai katt kovboy
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Re: Mid/Side Mux/Demux

Post by samrai katt kovboy » Wed Jan 16, 2013 4:02 pm

coffe is totally okay...

havent got soundcloud yet, but think that in about a month or two i have to finally to start posting on soundcloud and bandcamp!

time out to fly in... throughout.
SOOOOOOOOOOOOOOO MANY CIRCLES

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manganoid
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Re: Mid/Side Mux/Demux

Post by manganoid » Sun Oct 12, 2014 1:10 am

WOOOOOW, awesome :D
Again, Welldone mr Gilzad, kudos :D

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