Date:         Thu, 4 Dec 2008 01:23:22 -0000
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         Steve Abrams <[log in to unmask]>
Subject:      Re: "Difference Track"
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To help with the original question,
Adobe Audition has a feature, "Spectral Pan Display" a graphical
representation of panning between stereo channels. (can be used instead of
the standard waveform graphical representation)  Signal present on both
channels appears in the center, while signals stronger on one channel or
another appear closer to the top (left) or bottom (right) of the display.
You can then use their graphical editing tools to select either information
similar to both channels or the information unique to one channel or to the
other to process or delete.

This could be useful for stereo recordings of mono sound discs.  Grove
damage to a single channel / groove wall will only appear to the outside
edge of this graphical tool and can easily be taken out.  Same for grove
noise.
I have some mono tapes recorded over in stereo where the original recording is faintly audible in the part of the tape that was not erased.  The technique you discribe might facilitate the separation of this information from the new recording.  I can imagine this being of special importance in forensics. 

Steve Abrams
____________________________________________________________________________

I do not know your needs for these files but if your weren't already going
to,  I will suggest to also keep your original stereo file.  Regardless of
which software tool or trick you use to create your mono derivative.  These
tools still cause distortion, and the tools and processors are continuing to
get better,  so while you may be able to create a derivative mono file now
that may be good enough for your needs, the derivative file you create two
years from now from the same digital stereo source is only going to be
better,  plus digital storage is relatively cheap.
Hope this helps.

Tony Tadey

On 11/21/08 11:10 PM, "Garr Norick" <[log in to unmask]> wrote:

> Hello,
> 
> I have read that when mono recordings (such as Records and Cassettes) are
> Digitized in stereo, using stereo playback equipment, there is a "Difference
> Track"... i.e., on a digitized recording that originated from a cassette being
> played on a stereo deck, that one of the resulting channels will usually have
> a great deal more tape hiss, and lower fidelity, than the other... I have also
> read that certain digital recording/editing/restoration software (namely Adobe
> Audition, and Diamond Cut Pro) can find and eliminate this track, presumably
> by finding and eliminating any frequencies that are not common to the two
> channels... I have Diamond Cut Pro... is there anyone here who is familiar
> with Diamond Cut Pro, and can tell me how to use this function in the
> software? Thanks in advance.