Re: [ARSCLIST] 12 bit non-linear DAT and Sony LP mode

[Dave Rice <dave@xxxxxxxxxxxxxxxx>]

Hi ARSC list,
I'm glad 12 bit long play DAT tapes are a new topic on the list. I've  
been involved in a preservation project on these formats for a few  
months.

	Since this is born digital data it makes best sense to transfer  
digital stream off data directly off rather than do a digital to  
analog back to digital conversion. It makes the workflow faster,  
ensure a more accurate version of the original recording, and helps  
automate some of the quality control. I've read some concerns that  
anything recorded as 12bit long play mode wasn't intended on having  
great audio quality, so that unnecessarily making the audio analog  
and than back to digital isn't a significant loss. Most of the DAT  
tapes I work with our from journalists' fields recordings and often  
12 bit is used to save tape when funds or tape stock aren't  
available. Also with taking the digital stream off, it can be done in  
faster than real time and software can be enabled to log errors and  
record metadata in addition to the audio.

	I use a Sony DDS SDT-9000 drive to take this data off the tape and I  
find several advantages in treating DAT tapes as data tapes rather  
than audio tapes:

- the transfer work can be done in faster than real time (usually  
about 2x)

- data extraction software (plenty of freeware available to this  
task) can log error frames (getting a list of timecode associated  
with errors is much faster than having to do quality control by  
listening to the entire transfer)

- data extraction software can extract the audio as separate files  
based markers on the tape (does the signal coming out of SPDIF even  
pass this data). This advantage helps me quite a bit, because I'm  
working with journalists' fields recordings and knowing when they hit  
record and stop is helpful in cataloguing.

- data extraction software can generate metadata files for each  
program. For me this is a very important advantage. For each audio  
file extracted I can get a generated metadata file which states when  
the clock on the original recording deck was set to during the  
recording, as well as start and stop marker positions, durations,  
filesizes, audio properties, etc. I couldn't get my DAT player to  
present embedded timestamp info at all, but this needs to be  
preserved as well.

- the software is free, the data drives are probably about same cost  
as a DAT.

Also even though it's 12 bits of data. It's not the usual 12 bit  
recording. It's actually 16 with a lot of louder values missing. 16  
bit is 66536 values and 12 bit is 4096. The 12 bits (4096) represent  
selected values of the 66536 values, most of the values representing  
the quieter sounds.
Dave

David Rice
Archivist
Democracy Now!
87 Lafayette St.
New York, NY 10013
Phone: (212) 431-9090 x811
Fax: (212) 431-8858
Email: dave@xxxxxxxxxxxxxxxx


On Oct 10, 2007, at 7:45 PM, Tom Fine wrote:

> I was going to say what Richard said. I would add -- I can't  
> imagine that this content is such high fidelity that it will be  
> audibly degraded with a good D-A and then A-D chain. The advantage  
> is, you can hear unrecoverable errors in real time and mark them as  
> you go, you can mark edit points or track cuts as you go and you  
> may want to tweak EQ or dynamics in the analog realm to improve  
> audibility.
>
> So, satisfy our curiosity here:
>
> 1. what's on tapes made in that mode?
> 2. did they play OK on the Tascam deck?
>
> PS -- ping me off-list if you're having trouble getting them to  
> play. I am almost certain my Sony DAT deck will play this format.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Richard L. Hess"  
> <arclists@xxxxxxxxxxxxxxx>
> To: <ARSCLIST@xxxxxxxxxxxxxxxx>
> Sent: Wednesday, October 10, 2007 2:17 PM
> Subject: Re: [ARSCLIST] 12 bit non-linear DAT and Sony LP mode
>
>
> > At 02:02 PM 2007-10-10, andy kolovos wrote:
> > > Folks,
> > >
> > > Richard Hess--as always--has been wonderful in addressing a  
> > > series of questions I'm confronting, this time with some quirky  
> > > DATs. I feel I need to let him off the hook at this point as I am  
> > > sure he has better things to do than spend his day holding my  
> > > hand.  As such, now I am off to pester the lot of you.
> > >
> > > 1. Is this the same as the Sony LP mode, or did Sony do something  
> > > characteristic and create there own proprietary LP mode?
> >
> > What happens when you play it?
> >
> >
> > > 4. Assuming I can indeed get the tapes to play, does it make the  
> > > most sense to output it as an analog signal and then bring it  
> > > back into the digital domain via my A/D converter?
> >
> > If the digital links don't work then this is a good way to go. I  
> > wouldn't worry much about the A-D adding anything--assuming you're  
> > using your normal "good" chain and hopefully the D-A in the  
> > playback machine is good enough.
> >
> > > P.S. to those who are interested, I've opted to go with the Aphex  
> > > balancing amp based on Richard's thorough review.
> >
> > Glad to be of help.
> >
> > Cheers,
> >
> > Richard
> >
> > Richard L. Hess                   email: richard@xxxxxxxxxxxxxxx
> > Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
> > Detailed contact information: http://www.richardhess.com/tape/ 
> > contact.htm
> > Quality tape transfers -- even from hard-to-play tapes.