This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

Harry Lavo

I recently asked this same question regarding dbx noise reduction and the
general response was something like, "No, and you'd think that SOMEONE would
have coded such a thing. No clue as to why not."

Then one of our bretheren here graciously offered to lend me a hardware unit
to help me with my project. (Kudos to him!)

Seems to me that there are enough projects worth preserving on analog tape
still floating around that there is a genuine need for such software. I
don't have the expertise to program it, but somebody certainly should.

malachi


"Harry Lavo" wrote in message
. ..
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

Harry Lavo

Well, maybe two of us can form a lobbying firm? :-)

Harry

"malachi" wrote in message
et...
I recently asked this same question regarding dbx noise reduction and the
general response was something like, "No, and you'd think that SOMEONE
would have coded such a thing. No clue as to why not."

Then one of our bretheren here graciously offered to lend me a hardware
unit to help me with my project. (Kudos to him!)

Seems to me that there are enough projects worth preserving on analog tape
still floating around that there is a genuine need for such software. I
don't have the expertise to program it, but somebody certainly should.

malachi


"Harry Lavo" wrote in message
. ..
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

Harry Lavo

Harry Lavo wrote:
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

It doesn't exist. I don't know why. Lots of people have looked at doing
it and got partway through and given up. The guys at Plangent Processes
are still looking into it, though.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Harry,

does anybody know of any form of a plug in that would simulate a Dolby A
noise reduction device?

I once had to decode a dbx Type I tape and I got pretty close using a
multi-band compressor that could also operate as an expander. If you have a
similar plug-in and know the crossover frequencies for Dolby A you could
probably get pretty close.

--Ethan

"Scott Dorsey" wrote ...
Harry Lavo wrote:
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

It doesn't exist. I don't know why. Lots of people have looked at doing
it and got partway through and given up. The guys at Plangent Processes
are still looking into it, though.

Is the problem technical or legal?
Is the algorithm still protected (patent? copyright?)

I was under the impression that it was possible to do technically,
but Dolby Labs would not allow commercial exploitation.

Richard Crowley wrote:

Is the problem technical or legal?
Is the algorithm still protected (patent? copyright?)

I'm sure there's a patent involved. But Dolby is solidly in the
software business now. If they recognize that there's a market, I'm
sure they could whip something up in a couple of weeks, and there's
nobody better than Dolby to test it's performance.

I suspect that part of the issue may be that people will expect it to
be free or cheap and Dolby may want to keep that portion of the market
firmly locked up in hardware chips that they can sell for half a buck
and support the manufacturers who are using them in their equipment
rather than sell a program to end users who will then forever want to
know why it won't work with this or that computer.

Richard Crowley wrote:
"Scott Dorsey" wrote ...
Harry Lavo wrote:
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

It doesn't exist. I don't know why. Lots of people have looked at doing
it and got partway through and given up. The guys at Plangent Processes
are still looking into it, though.

Is the problem technical or legal?
Is the algorithm still protected (patent? copyright?)

Dolby A is no longer under patent. dbx Type I isn't either. Dolby SR
definitely is. Telcom C is not. Dolby B and dbx Type II, I dunno about.

I was under the impression that it was possible to do technically,
but Dolby Labs would not allow commercial exploitation.

It should be possible to do technically, but I gather it's not as easy
as it looks at first. Then again, it might be good enough just to get
close, for many applications.

I don't think Dolby has any control over the Dolby A process any more,
although they sure have a lot of control over SR.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Richard Crowley" wrote in
message
"Scott Dorsey" wrote ...
Harry Lavo wrote:
This is kind of a naive question, but does anybody know
of any form of a plug in that would simulate a Dolby A
noise reduction device? In other words, allow you to
digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means
of archiving, or alternatively decode it on the fly
while recording? If such exists, I'd like to know
about it. And if not, any speculation as to why not?

It doesn't exist. I don't know why. Lots of people
have looked at doing it and got partway through and
given up. The guys at Plangent Processes are still
looking into it, though.

Is the problem technical or legal?
Is the algorithm still protected (patent? copyright?)

I was under the impression that it was possible to do
technically, but Dolby Labs would not allow commercial
exploitation.

Since Dolby A is 1960s technology, any directly relevant patents have no
doubt run out. However, the good ways to do it in software were probably
patented far more recently.

We have a very complicated Logic Environment that decompresses Dolby A
pretty well. I can't claim that we are exact, and I don't want to get
in trouble with Dolby. We have done the best we can with what published
information is available. It works pretty well, but I can't and won't
sell it. They claim that some of the analog sloppiness is what makes it
work well (I think they're talking about a recursive compression curve
that actually goes negative). There's also some question about ideal
attack rates. If the attack rates are truly as fast as the circuit
would imply then there's always been some distortion in the sidechain.
Dolby claims it's impossible, and who am I to disagree. But a/b ing
with a real 361 I can't hear a difference except that the 361 seems to
pump more.

DBX, by the way, would be really easy, by comparison.

Jamie Howarth
Plangent Processes

Scott Dorsey wrote:
Harry Lavo wrote:
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

It doesn't exist. I don't know why. Lots of people have looked at doing
it and got partway through and given up. The guys at Plangent Processes
are still looking into it, though.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Thanks, Jamie and Scott. My first question has been answered, and you have
gone a long way to answering the second. Guess I'll just have to refurbish
and recalibrate my old pair of 361's.

Harry Lavo

wrote in message
oups.com...
We have a very complicated Logic Environment that decompresses Dolby A
pretty well. I can't claim that we are exact, and I don't want to get
in trouble with Dolby. We have done the best we can with what published
information is available. It works pretty well, but I can't and won't
sell it. They claim that some of the analog sloppiness is what makes it
work well (I think they're talking about a recursive compression curve
that actually goes negative). There's also some question about ideal
attack rates. If the attack rates are truly as fast as the circuit
would imply then there's always been some distortion in the sidechain.
Dolby claims it's impossible, and who am I to disagree. But a/b ing
with a real 361 I can't hear a difference except that the 361 seems to
pump more.

DBX, by the way, would be really easy, by comparison.

Jamie Howarth
Plangent Processes

Scott Dorsey wrote:
Harry Lavo wrote:
This is kind of a naive question, but does anybody know of any form of a
plug in that would simulate a Dolby A noise reduction device? In other
words, allow you to digitize a tape directly without decoding, and then
decode it within the DAW to alternate tracks as a means of archiving, or
alternatively decode it on the fly while recording? If such exists, I'd
like to know about it. And if not, any speculation as to why not?

It doesn't exist. I don't know why. Lots of people have looked at doing
it and got partway through and given up. The guys at Plangent Processes
are still looking into it, though.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Harry Lavo wrote:
Thanks, Jamie and Scott. My first question has been answered, and you have
gone a long way to answering the second. Guess I'll just have to refurbish
and recalibrate my old pair of 361's.

Fortunately, unlike software, hardware can continue to be made healthy.