Re: arsclist Transfer of multiple copies, was: Full 3-D mapping of groove?

["Doug Pomeroy" <pomeroyaudio@xxxxxxx>]

Not to beat a dead horse, but:

Below is Gordon Reid's reply to my question about the CEDAR
azimuth corrector.

Whatever one chooses to call it, the point is that, on the basis of
signal common to both channels, the right channel is regenerated
and moved forward or back in time to be in sync with the left. And,
this is what is needed to optimize the L+R mix of the outputs of a
stereo phono cartridge playing a mono record, to achieve the best
signal to noise ratio.

The "regeneration" is presumably that form of digital signal processing
which allows duration to be changed without changing pitch (and vice
versa).

Doug Pomeroy   pomeroyaudio@xxxxxxx
Audio Restoration & Remastering Services
----
> From: Gordon Reid <gordon@xxxxxxxxxxxxxxx>
> To: <pomeroyaudio@xxxxxxx>
> Subject: CEDAR Azimuth Correctors
> Date: Wed, Dec 18, 2002, 3:06 PM
>
> Hello Doug,
>
>>There was an exchange recently on the ARSC listserve about
>>the CEDAR Azimuth Corrector, and whether it "shifts phase"
>>or actually changes pitch. I claim the latter. Am I right?
>
> Neither description is quite right.
>
> The AZ does not shift the phases of individual frequencies, as your
> correspondent suggested, so to some extent the original name of "phase
> corrector" was misleading. The algorithm works on the signal as a whole,
> shifting it in time so that the lagging channel is realigned with the
> leading channel. However, it does not do this by pitch shifting, either.
> Rather, it regenerates the lagging signal so that the common content of
> the stereo pair is time aligned. If the lead signal suffers from pitch
> shift - say, a slow wow - then the regenerated signal will also exhibit
> this, but this is then a consequence of the genuine signal, not of the
> algorithm.
>
> There is a lot more information about this on the CEDAR website. Please
> click on "Introduction To Audio Restoration" followed by "Azimuth
> Correction".
>
> I hope that this helps.
>
> Best regards,
>
> Gordon.
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