Mid-Side decoding

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Keith Taylor
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Mid-Side decoding

Post by Keith Taylor » Tue Jun 03, 2014 6:09 pm

I have Audacity 2.0.5 installed on a computer running Win Vista Home Premium. Nuances of version and OS are probably irrelevant to my question, which is, Does Audacity have an M-S decoding function?

I record in M-S format so it is fundamental that any editing software I use should be able to convert M-S to stereo. The basic operations are-

Left channel=M+S and Right channel =M-S.

It is often done with 3 mixer channels in hardware or software. There is nothing particularly special about the mixer channels except that at least one of them needs a phase invert function on its input, and that this channel, and another, have to be fed with the same input signal. We get subtraction (M-S) by summing/mixing the two signals in antiphase.

Anyone had any experience in doing this operation in Audacity?

Keith
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steve
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Re: Mid-Side decoding

Post by steve » Tue Jun 03, 2014 6:23 pm

To invert a track, use "Effect > Invert".
You may also need to split / join stereo tracks: http://manual.audacityteam.org/o/man/sp ... racks.html
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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Robert J. H.
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Re: Mid-Side decoding

Post by Robert J. H. » Tue Jun 03, 2014 6:34 pm

You can also download Steve's channel-mixer plug-in.
One of the presets (e.g. left to center) is what you want.
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steve
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Re: Mid-Side decoding

Post by steve » Tue Jun 03, 2014 6:58 pm

Robert J. H. wrote:You can also download Steve's channel-mixer plug-in.
Available here: http://wiki.audacityteam.org/wiki/Nyqui ... nnel_Mixer
Installation instructions: http://wiki.audacityteam.org/wiki/Downl ... g_Plug-ins
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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Keith Taylor
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Re: Mid-Side decoding

Post by Keith Taylor » Wed Jun 04, 2014 2:40 pm

Steve and Robert, thanks for your prompt and helpful responses. For the plugin to do what it is capable of tends to indicate that it is doing sum and difference operations on the stereo signals and finally restoring them to stereo. This suggests that M-S decoding is possible.

Keith
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steve
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Re: Mid-Side decoding

Post by steve » Wed Jun 04, 2014 5:59 pm

The plug-in is written in a scripting language called "Nyquist".
Nyquist plug-ins are plain text files, so can easily be edited in any plain text editor (such as NotePad or NotePad++)

You can read about Nyquist plug-ins here: http://wiki.audacityteam.org/wiki/Nyqui ... _Reference
and we have a forum board specifically for things to do with Nyquist: http://forum.audacityteam.org/viewforum.php?f=39
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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themickster
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Re: Mid-Side decoding

Post by themickster » Tue Sep 15, 2015 10:27 pm

Why does there need to be the phase difference between the two sides? Don't they cancel each other?
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