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I agree with James.  
If decoding can be done all digitally, so much the better.
 If tweaking of the input to the decoder is necessary for minimum
artifacts, I'd rather experiment on the digital copy, avoiding
wear/damage to the analog carrier with multiple passes. It also avoids
an extra DA and AD conversion stage and any associated gain errors.

Even so, there's still the need to carry over NR alignment references
into digital. This makes no sense to the person who doesn't understand
how level sensitive some systems are like Dolby B,C,S.
 
There's also still the occasional issue of  identifying an unlabelled
recording as possibly Dolby x  / ? encoded,  purely by listening to
the audio, which involves knowing by experience what a particular
system likely does to the sound.  I discovered some years ago in a
team situation that t
hese listening skills aren't necessarily easily taught.

Tim Gillett

Perth,
Western Australia  

   

----- Original Message -----
From:
 [log in to unmask]

To:
<[log in to unmask]>
Cc:

Sent:
Mon, 15 Jul 2019 14:50:07 +0100
Subject:
Re: [ARSCLIST] [EXTERNAL] [ARSCLIST] Preserving both raw and decoded
files for tapes recorded with Noise Reduction?

 While I'm probably not as expert as some on this list, my standard
practice
 is to do a flat transfer at 96kHz/24 bits and then carry out any
noise
 reduction as a separate process. This allows me to concentrate on the
tape
 transfer without having to worry about calibrating the noise
reduction at
 the same time. I could also experiment with different hardware or
software
 at a later date. Storage is cheap - especially when using .FLAC files
as
 intermediate files so nearly every step is kept.

 Cheers,

 James.

 On Mon, 15 Jul 2019 at 06:24, Shai Drori <[log in to unmask]> wrote:

 > Jamie please contact me off list.
 >
 > Cheers
 > Shai Drori
 > Expert digitization services for Audio Video
 > 3K scanning for film 8mm-35mm
 > Timeless Recordings Music Label
 > www.audiovideofilm.com
 > [log in to unmask]
 > Tripadvisor level 6 contributor, level 15 restaurant expert
 >
 >
 > On Sun, Jul 14, 2019 at 10:27 PM Abhimonyu Deb <
 > [log in to unmask]> wrote:
 >
 > > Hi Richard,
 > > As to my question, am I the only proponent of recording the raw,
 > > undecoded output? It's saved my bacon more than once, and I've
been
 > > insisting on it for at least a decade. I was hoping that some
 > > standards/best practice body recommended it. I did not think I
was alone.
 > > IASA-TC 03 (2017) addresses this in a very, very general and
vague sense.
 > > It says in chapter 7 (Optimal signal retrieval from original
carriers),
 > in
 > > the last paragraph before "Comments":
 > > As in other fields of historical research, the use of cautiously
chosen
 > > approximations is permissible when necessary. As a matter of
principle,
 > > however, all such decisions must be documented, and irreversible
steps
 > > should be avoided. All unnecessary subjective treatments must
only be
 > > applied to access copies.
 > >
 > > Although Dolby A is hardly subjective, it may be prone to error
if not
 > > played back correctly and, therefore, may fall within this
clause.
 > > The document also states in the previous paragraph:
 > > Digital carrier-based formats may contain various types of
sub-code
 > > information, that is, secondary information written in parallel
with the
 > > primary information bitstream. Incompatibilities between
recording and
 > > replay devices can result in this information being retrieved
incorrectly
 > > or not at all. Understanding the properties of a given format or
 > > collection, including any sub-code information, and defining the
minimum
 > > required combination of primary and secondary information prior
to its
 > > digitisation, is of utmost importance (see section 2).
 > > Although this is about digital carriers, if we extend the logic
to the
 > > analog domain, shouldn't it apply to the recording of the bias
frequency
 > as
 > > well? It's a long stretch, but I was just thinking.
 > > Cheers,
 > > Abhimonyu DebAudio Consultant and Digitization Specialisthttps://
 > > www.linkedin.com/in/abhimonyudeb
 > >
 > >
 > > On Monday, 15 July, 2019, 06:25:06 am IST, Richard L. Hess <
 > > [log in to unmask]> wrote:
 > >
 > > Hi, Corey and Gary,
 > >
 > > Thanks for your kind remarks about the decoder. My colleague and
friend,
 > > John Dyson has done a wonderful job with the code. His acid tests
have
 > > been leaked Dolby recordings of 70s pop music--some of them sound
so bad
 > > until he decodes them...but they are tougher than the stuff I've
 > > recorded and obtained from other sources.
 > >
 > > What has happened is the intermod that is normally generated by
fast
 > > gain changes on decoding is vastly reduced.
 > >
 > > As to my question, am I the only proponent of recording the raw,
 > > undecoded output? It's saved my bacon more than once, and I've
been
 > > insisting on it for at least a decade. I was hoping that some
 > > standards/best practice body recommended it. I did not think I
was alone.
 > >
 > > John Chester, thanks for the info on 384 kHz sampling frequency
and bias.
 > >
 > > Remember my effort here?
 > >
http://richardhess.com/notes/2008/02/02/tape-recorder-bias-frequencies/
 > >
 > > The only major recorders that are problematic (i.e. bias
frequencies
 > > above 180 kHz are:
 > >
 > > Ampex ATR-100 (432 kHz)
 > > Sony APR-5000 and probably multitracks (400 kHz)
 > > Studer A80VU (240 kHz, most late models are 150 or 153.6 kHz,
 > > the A77 is 120 kHz)
 > > Otari MTR-10/12 and MTR-90 (246-250 kHz)
 > >
 > > Cheers,
 > >
 > > Richard
 > >
 > >
 > > On 2019-07-14 7:16 p.m., Gary A. Galo wrote:
 > > > Hi Richard,
 > > >
 > > > I echo Corey Bailey's email in congratulating you on the
software-based
 > > NR decoder. I'm sure there will be a considerable market for it.
 > > >
 > > > The issue of preserving the "original" data - whether analog of
digital
 > > - is a sticky and controversial one. When I gave my ARSC
presentation on
 > > transferring PCM-F1 format digital recordings for the NY ARSC
chapter
 > April
 > > 2018, I was taken to task by one attendee for not preserving the
original
 > > bits. I go from the S/PDIF output of my PCM-601ESD digital
processor
 > > directly into a Tascam DA-3000 digital recorder. The Tascam has a
 > built-in,
 > > switchable sample rate converter based on the Cirrus Logic CS8422
SRC
 > chip
 > > (which doubles as the S/PDIF input receiver). I set the Tascam to
record
 > at
 > > 88.2 kHz, so the CS8422 is converting 44.056 to 88.2. An
"undocumented
 > > feature" of the DA-3000 recorder is that the CS8422 SRC chip also
does
 > > 50/15 uSec de-emphasis, which take care of another issue with F1
 > > recordings. Why Tascam fails to mention this anywhere in their
manual or
 > > product literature is beyond me, because the de-emphasis feature
is
 > clearly
 > > stated on the front page of the CS-8422 data sheet, and it's an
extremely
 > > useful feature.
 > > >
 > > > With this method, only the inter-channel time delay and DC
offset still
 > > need to be addressed once the 88.2 kHz data is on your computer.
 > > >
 > > > My method does not save the original 44.056 kHz bits. Guilty as
 > charged.
 > > But, the CS8422 does a beautiful job with the SRC and the
de-emphasis,
 > and
 > > has ultra-low jitter clock recovery to boot, so I sleep well at
night. If
 > > you feel the need to preserve the original bits, you could run a
second,
 > > raw transfer directly into your computer, if your computer will
lock onto
 > > 44.056 kHz. Or, you could use a digital distribution device to
split the
 > > 44.056 kHz data stream, sending it to both the computer, and the
DA-3000
 > > recorder simultaneously. But, I just don't see the need.
 > > >
 > > > So there is no misunderstanding, I can well understand the
desire to
 > > preserve the non-decoded Dolby-A analog signal in case better
software
 > > conversion becomes available down the road. It makes sense to do
this.
 > So,
 > > perhaps I'm being inconsistent. These are thorny issues, and
everyone
 > will
 > > have their own viewpoints.
 > > >
 > > > Best,
 > > > Gary
 > > >
 > > > ____________________________
 > > >
 > > > Gary Galo
 > > > Audio Engineer Emeritus
 > > > The Crane School of Music
 > > > SUNY at Potsdam, NY 13676
 > > >
 > > > "Great art presupposes the alert mind of the educated
listener."
 > > > Arnold Schoenberg
 > > >
 > > > "A true artist doesn't want to be admired, he wants to be
believed."
 > > > Igor Markevitch
 > > >
 > > > "If you design an audio system based on the premise that
nothing is
 > > audible,
 > > > on that system nothing will be audible."
 > > > G. Galo
 > > >
 > > > -----Original Message-----
 > > > From: Association for Recorded Sound Discussion List [mailto:
 > > [log in to unmask]] On Behalf Of Richard L. Hess
 > > > Sent: Sunday, July 14, 2019 5:42 PM
 > > > To: [log in to unmask]
 > > > Subject: [EXTERNAL] [ARSCLIST] Preserving both raw and decoded
files
 > for
 > > tapes recorded with Noise Reduction?
 > > >
 > > > Hi, I think many of us agree that it's necessary to preserve
both the
 > > > raw transfer and the decoded version of a file which has been
recorded
 > > > with Dolby or DBX type noise reduction.
 > > >
 > > > When I first thought about it, I never imagined I'd be part of
a team
 > > > that would produce a better decoder for Dolby A encoded tapes
than
 > > > Dolby, but it's happening and humbling... So, it is a good idea
to save
 > > > as much raw data as possible because who knows what else will
come
 > along.
 > > >
 > > > Plangent is wonderful, but a bit problematic as it is still
 > inconvenient
 > > > to properly archive the bias, but that's another story, and I
think in
 > > > the long run it would be good if we could do that.
 > > >
 > > > MY QUESTION is: Are there any standards or recommendations that
say
 > > > "keep the raw undecoded copy as well as keeping the decoded
copy?
 > > >
 > > > It's for a paper that Federica and I are writing.
 > > >
 > > > Thanks!
 > > >
 > > > Cheers,
 > > >
 > > > Richard
 > > >
 > >
 > > --
 > > 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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 * James Perrett
 * JRP Music Services, Alresford, Hampshire, U.K.
 * Audio Mastering, Restoration, Recording and Consultancy
 * Phone +44 (0) 777 600 6107
 * e-mail [log in to unmask]
 * http://www.jrpmusic.net
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