ProTools - how to reduce stereo file to center image only?

Archived from groups: rec.audio.pro (More info?)

ProTools - how can I reduce a stereo file to center image only?

Everyone knows the phase flip trick that removes all information
common to left and right channels. (left summed with out-of-phase
right channel.) It's the poor man's vocal elimination trick.

So I'm stymied - how can I remove information NOT common to left and
right? I'm doing a forensics job and there is video tracking noise in
the left and right channels, and it's not in the center. Any way to do
this? I have a full Waves collection and a few Digi plugs.

I could do it externally with a Dolby Prologic decoder, but this is
eight hours of audio. I need to do it as a batch job.

This comes up often enough that I need a permanent cure.




Thanks -

Kurt Riemann

Archived from groups: rec.audio.pro (More info?)

Put the Waves MS-Matrix on the stereo track and bus the track´s output to
e.g. busses 1-2.
What´s coming in on bus 1 is the M signal only.

Is this what you need?

Peter
---
http://www.merlinsound.de

Kurt Riemann wrote:
> ProTools - how can I reduce a stereo file to center image only?
>
> Everyone knows the phase flip trick that removes all information
> common to left and right channels. (left summed with out-of-phase
> right channel.) It's the poor man's vocal elimination trick.
>
> So I'm stymied - how can I remove information NOT common to left and
> right? I'm doing a forensics job and there is video tracking noise in
> the left and right channels, and it's not in the center. Any way to do
> this? I have a full Waves collection and a few Digi plugs.
>
> I could do it externally with a Dolby Prologic decoder, but this is
> eight hours of audio. I need to do it as a batch job.
>
> This comes up often enough that I need a permanent cure.

Archived from groups: rec.audio.pro (More info?)

On Sun, 11 Sep 2005 19:27:34 -0400, "Zigakly" <no@no.no> wrote:

>
><Kurt Riemann> wrote in message
>news:gfc9i11kh42v01g8a36epkopo1fs8ulbkv@4ax.com...
>> ProTools - how can I reduce a stereo file to center image only?
>>
>> Everyone knows the phase flip trick that removes all information
>> common to left and right channels. (left summed with out-of-phase
>> right channel.) It's the poor man's vocal elimination trick.
>>
>> So I'm stymied - how can I remove information NOT common to left and
>> right? I'm doing a forensics job and there is video tracking noise in
>> the left and right channels, and it's not in the center. Any way to do
>> this? I have a full Waves collection and a few Digi plugs.
>
>Take the "vocal eliminated" track and inverse that against the standard mono
>sum?
>

No, Left would sum with the "vical eliminated" track because left was
never inverted in either process. So any noise on the left would be
reinforced, not eliminated.



Kurt Riemann

Archived from groups: rec.audio.pro (More info?)

On 9/11/05 10:12 PM, in article
1126491160.482356.243410@z14g2000cwz.googlegroups.com, "Mark"
<makolber@yahoo.com> wrote:

>
> Kurt Riemann wrote:
>> ProTools - how can I reduce a stereo file to center image only?
>>
>> Everyone knows the phase flip trick that removes all information
>> common to left and right channels. (left summed with out-of-phase
>> right channel.) It's the poor man's vocal elimination trick.
>>
>> So I'm stymied - how can I remove information NOT common to left and
>> right? I'm doing a forensics job and there is video tracking noise in
>> the left and right channels, and it's not in the center. Any way to do
>> this? I have a full Waves collection and a few Digi plugs.
>>
>> I could do it externally with a Dolby Prologic decoder, but this is
>> eight hours of audio. I need to do it as a batch job.
>>
>> This comes up often enough that I need a permanent cure.

Dang it we just DID this thread a few weeks back.
Dolby Pro Logic can derive a SORT of center-only channel but that it can do
it at all is damned amazing, and it's hardly perfect. Beyond that, you
pretty much can't... Though as a forensics job you're not concerned with
perfection.
What dedicated forensic audio tools are you using?
There are a couple systems that can dig through this with some success, if
you've had no success with them then there may not be a better result.

Archived from groups: rec.audio.pro (More info?)

On Sun, 11 Sep 2005 18:08:15 -0800, Kurt Riemann <> wrote:

>>Take the "vocal eliminated" track and inverse that against the standard mono
>>sum?
>>
>
>No, Left would sum with the "vocal eliminated" track because left was
>never inverted in either process. So any noise on the left would be
>reinforced, not eliminated.

Yeah, the Dolby stuff includes gain-riding. No amount
of summing and differencing can do any better than
L+R and L-R. Ain't (as you point out) there.

In a DAW, one could compress the diff.

Chris Hornbeck

Archived from groups: rec.audio.pro (More info?)

It is not correct but:

Put 3 plugins: in order

M/S matrix
some eq
M/S matrix again

From the eq bring down the L signal (the M) to -infinite

You will have only a (false) stereo signal without the M...

Sometimes it works well...
F.