As noted, the use of 12 bits is not linear but it's a selection of some of the values of the 16 bit range that are mapped to 12. AFAIK all of the DAT rippers that support 12 bit do so with a lookup table in order to map the 12 bit value to the corresponding 16 bit value. For instance see the decode_lp_sample function, https://github.com/andrew-taylor/read_dat/blob/master/read_dat.c#L1067, which is used in both DatXtract and read_dat.
> On May 2, 2017, at 3:15 PM, Eli Bildirici <[log in to unmask]> wrote:
> Hey Lou and Ted,
> Appreciate it but I'm trying to avoid the quality loss, however minor, of a D-A-D conversion. Once the 12-bit files are created, resampling to a more standard format e.g. Redbook should be trivial by using a good resampler like SoX (or Izotope if you could afford it) right? In any case there is also Redbook and possibly 48kHz content on these tapes and it just seems silly to do D-A-D on those, lacking even the motive of moving to a more standardized format. I'm only even asking for this because I figured it would be beneficial to know an alternative to the preferred way of making these copies (DSS drives and ReadDAT or DATXtract). Of course if neither of these ways work out, doing a D-A-D conversion will have to do, and probably won't make much of a difference given that there is very little content here that isn't straight-up voice (we're a radio show after all). But it's still not ideal :/ In any case, thanks for chiming in.
>> May 2 2017 2:48 PM, "Ted Kendall" <[log in to unmask]> wrote:
>> If memory serves, the 12-bit convertors were non-linear anyway. Best to
>> convert to something civilised via analogue.
>> May 2 2017 2:24 PM, "Lou Judson" <[log in to unmask]> wrote:
>> Sigh, nonstandard formats are a problem!
>> But as a small time archivst myself, I would take the analog outut of the deck and re-encode it at
>> 16 bit for archiving purposes. There is no way you waould actually want “bit-perfect” 12 bit files,
>> as that would just pass the problem down to your successors.
>> Play the DATs, record the output in a normal format, and it will be far better than any kluge you
>> can do with 12 bit digital.
>> I used Sony 12 bit 32kHz for some extended recordings back in the day, and this was the best way I
>> found for the transfer.
>> I’ll be interested to see if anyone has a better suggestion!
>> Lou Judson
>> Intuitive Audio
>> On May 2, 2017, at 10:56 AM, Eli Bildirici <[log in to unmask]> wrote:
>>> Hey ARSClisters,
>>> I'm an intern in the archives department at Democracy Now! and have come across a couple hundred
>>> mixed-frequency DAT tapes, many of which have 12-bit/32kHz content on them. (And yes, this is the
>>> same issue an archivist from DN! posted about nearly ten years ago, here
>>> (http://www.cool.conservation-us.org/byform/mailing-lists/arsclist/2007/07/msg00380.html).) We'd
>>> like to make bit-perfect digital copies, but don't have a SCSI DDS drive at the moment, and in any
>>> case would like to know if there's a reliable alternative path to digitally copying DATs,
>>> especially those recorded at a bit-depth of 12, via S/PDIF and capture cards. I attempted to copy a
>>> portion of a tape recorded at Redbook rates using our main deck - a Sony PCM-R500 - with an M-Audio
>>> FireWire Solo and Audacity to record, but this was full of pops and clicks that, I assume, are the
>>> result of the M-Audio failing to lock onto the tape deck's clock. (The pops and clicks only show up
>>> during recording and are not on the tape itself. Actually, I suspect Audacity may in part be to
>>> blame, since the pops and clicks are absent when monitoring via the M-Audio control panel app on OS
>>> X...but I digress.) I've also found that external sound cards based on the C-Media CM6206 chipset -
>>> cheap and plentiful on eBay - reportedly support 16-bit/32kHz input, as does the S/PDIF input of
>>> our aging PowerMac G5. But that doesn't help us with 12-bit content, and nor do we know whether
>>> clock syncing will pose an issue and how to deal with it if it does. My suspicion is that, while
>>> there might be an economical and reliable solution to recording DAT tapes with 16-bit content (at
>>> least at 44.1 or 48 kHz sample rates) without a DDS drive, that we're out of luck for 12-bit
>>> content - but, any advice/confirmation/refutation would be most welcome.
>>> Eli Bildirici
>>> (347) 837-8337
> Eli Bildirici
> (347) 837-8337