[Chris Hornbeck]

On Tue, 28 Oct 2008 17:46:49 -0700, "William Sommerwerck"
wrote:

185nW/m comes to mind. Yes, it is my recollection that there were
cassettes that were recorded with peaks above Dolby level. I'm not
sure that this is as Dolby intended, but it did happen.

I think 185nW/m is the right reference level.

Dolby reference level for cassttes is 200nW/m at 400Hz. Various levels
including 160 (early STL), 185 (many type 1 tapes), and 250 (type 2
tapes) were considered "operating level" in the cassette era and were
0VU during recording.

Larger and faster tapes will likely have even higher headroom
requirements, so a digital FS at Dolby level is a big mistake.
Yikes.

Much thanks, as always,
Chris Hornbeck

[Andre Majorel]

On 2008-10-27, Don Pearce wrote:
Joe the audio guy wrote:
Another quick question: Is Dolby B/C available as software
and, if not, why?

It would be totally pointless. Once you have the signal rendered into
numbers, there are no longer any dynamic range limitations that would
merit Dolby (B or C).

All the cassettes I recorded with Dolby B sound wrong on play
back. With Dolby on, they sound like they're going through a
low-pass filter that is lifted for a few milliseconds every now
and then. Without it, there's hiss and mids/highs boost.

It would be nice if there was a Dolby B decoder where you could
tweak the parameters until it suck less. Don't know if it being
software would help, or if it is even theoretically possible
but I can understand why someone would want that.

--
André Majorel URL:http://www.teaser.fr/~amajorel/
You measure democracy by the freedom it gives its dissidents, not
the freedom it gives its assimilated conformists -- Abbie Hoffman.

[Don Pearce]

Andre Majorel wrote:
On 2008-10-27, Don Pearce wrote:
Joe the audio guy wrote:
Another quick question: Is Dolby B/C available as software
and, if not, why?
It would be totally pointless. Once you have the signal rendered into
numbers, there are no longer any dynamic range limitations that would
merit Dolby (B or C).

All the cassettes I recorded with Dolby B sound wrong on play
back. With Dolby on, they sound like they're going through a
low-pass filter that is lifted for a few milliseconds every now
and then. Without it, there's hiss and mids/highs boost.

It would be nice if there was a Dolby B decoder where you could
tweak the parameters until it suck less. Don't know if it being
software would help, or if it is even theoretically possible
but I can understand why someone would want that.


There is an even chance that the error was on recording or playback. Or
you may just be sensitive to the way Dolby sounds.

d

[John Williamson]

Andre Majorel wrote:
On 2008-10-27, Don Pearce wrote:
Joe the audio guy wrote:
Another quick question: Is Dolby B/C available as software
and, if not, why?
It would be totally pointless. Once you have the signal rendered into
numbers, there are no longer any dynamic range limitations that would
merit Dolby (B or C).

All the cassettes I recorded with Dolby B sound wrong on play
back. With Dolby on, they sound like they're going through a
low-pass filter that is lifted for a few milliseconds every now
and then. Without it, there's hiss and mids/highs boost.

It would be nice if there was a Dolby B decoder where you could
tweak the parameters until it suck less. Don't know if it being
software would help, or if it is even theoretically possible
but I can understand why someone would want that.

If it's just for playback, there's a restoration plugin available for
Winamp that does that and a lot more.

http://www.winamp.com/plugins/details/154246

Get the settings right, then use the .wav file export feature on Winamp.

It's a bit of a kludge, but it works for me, and it's free.

--
Tciao for Now!

John.

[William Sommerwerck]

It would be nice if there was a Dolby B decoder where you could
tweak the parameters until it suck less. Don't know if it being
software would help, or if it is even theoretically possible
but I can understand why someone would want that.

In my opinion, the problem lies with the peak clipping during the encode
cycle. I believe it causes mistracking that results in the (almost certainly
correct) perception that Dolby B dulls the sound.

[Scott Dorsey]

Andre Majorel wrote:
On 2008-10-27, Don Pearce wrote:
Joe the audio guy wrote:
Another quick question: Is Dolby B/C available as software
and, if not, why?

It would be totally pointless. Once you have the signal rendered into
numbers, there are no longer any dynamic range limitations that would
merit Dolby (B or C).

All the cassettes I recorded with Dolby B sound wrong on play
back. With Dolby on, they sound like they're going through a
low-pass filter that is lifted for a few milliseconds every now
and then. Without it, there's hiss and mids/highs boost.

This is mistracking and it's caused because the Dolby level does not
match on the encoder and decoder.

It would be nice if there was a Dolby B decoder where you could
tweak the parameters until it suck less. Don't know if it being
software would help, or if it is even theoretically possible
but I can understand why someone would want that.

There are. Dolby has made one for the past 30 years. Combining it with
an equalizer can help a little although setting the equalizer up can be
problematic.

You can also find outboard Dolby B decoders from outfits like Tascam and
Concord, selling very cheaply on the used market.
--scott


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