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Jamie please contact me off list.

Cheers
Shai Drori
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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.
>
>