Hi, Matt,
The interrupted tone for Dolby A is merely an identifier. There is no
magic in that tone.
My understanding is that pristine NR units were measured and modelled to
create the NR plug-ins.
Corey,
Dolby A is four bands and is only added (or subtracted) starting at
about twenty decibels below Dolby tone.
Yes the lineup tones need to be accurately calibrated or the
addition/subtraction will start to happen at the wrong level.
This is why I use the output level control of my cassette machines and
the room monitor knob so it becomes easy to tune the input level to the
outboard Dolby B decoder so that the pumping goes away. Too much level
and the decays are overly bright. Too little level and the decays go
muddy as the filter closes down too soon. The idea of adjusting both is
to provide a constant listening level.
Someone else (from Australia, I believe) uses a graphic EQ ahead of
Dolby decode to try and re-flatten frequency response on Dolby-encoded
cassettes.
Cheers,
Richard
On 2015-08-07 4:58 PM, Matt Sohn wrote:
> I have been waiting for a software solution to Dolby encoding for years.
> I got the impression that Dolby was not inclined to give out the
> proprietary information that software developers would need to
> accurately emulate the functions. Perhaps this has changed, or the
> developers have managed to back-engineer the process. I know that the
> dolby process is highly dependent on an accurate warble tone, so I'm
> curious how this is dealt with in software. If I remember correctly,
> Dolby A uses fixed frequency bands, but in SR the frequency bands are
> sliding depending on the amplitude. This would be hard to emulate in
> software, I would think..
>
> -Matt Sohn
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Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.
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