 |
 |
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. > > > > > -- ********************************************************************** * 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 **********************************************************************