As to Richards request, " I was hoping that some standards/best 
practice body recommended it." there is a plethora of organizations 
involved, and until they have an umbrella meeting, I'm not sure such 
will happen.
     Among these are the
         AES,
         ARSC,
         Cool http://cool.conservation-us.org/bytopic/audio/ ,
         The National Archive, 
https://www.archives.gov/preservation/formats/audio-video-resources
         Those listed at the Library of Congress: 
https://www.loc.gov/programs/national-recording-preservation-board/resources/organizations/ 
 From the National Recording Preservation Board 
<https://www.loc.gov/programs/national-recording-preservation-board/>
         the LC's own Recorded Sound Research Center: 
https://www.loc.gov/rr/record/
           And... LC bibliography: 
https://www.loc.gov/programs/national-recording-preservation-board/resources/audio-preservation-bibliography/
     And various Universities are now putting courses up regarding 
preservation: 
http://www.nyu.edu/tisch/preservation/program/14fall/intro-syllabus14.shtml

     It seems, tying all this together under a single group, would be 
one of those listed [perhaps ARSC/IASA]...although another group started 
a while back wanting to be the umbrella for all of this digital 
preservation:
Thus: Foreword The Digital Preservation Coalition (DPC) is an advocate 
and catalyst for digital preservation, ensuring our members can deliver 
resilient long-term access to digital content and services. 
*https://dpconline.org/*

My own take on 'best practices' is that they usually work for specific 
organizations, specific needs, and specific missions; not every body is 
in the same apple orchard. Standards on the other hand is somewhat 
worthwhile, although we still have different threading on our cars, 
electronic equipment, et al; which we try to repair. [an aside: I ended 
up buying my own threading equipment.]

Paul Jackson
Trescott Research

On 7/14/2019 5:53 PM, Richard L. Hess 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
>>
>