km456265@longs.LANCE.ColoState.Edu (Kevin Melsheimer) (04/26/91)
Has anyone heard any information about the new digital format that is coming out sometime this summer? Is the new RDAT system supposed to be as good as existing DAT systems? How will the new Philips deck analog end stand up to normal tape players (the new dcc format I've heard will be able to play normal audio cassettes) What will the dynamic range be like? Thanks in advance, Kevin Melsheimer
winalski@psw.enet.dec.com (Paul S. Winalski) (04/29/91)
In article <11436@uwm.edu>, km456265@longs.LANCE.ColoState.Edu (Kevin Melsheimer) writes: |> |>Has anyone heard any information about the new digital format that |>is coming out sometime this summer? Is the new RDAT system supposed |>to be as good as existing DAT systems? The new format is not RDAT (rotating-head DAT). It is SDAT (stationary-head DAT). On the chosen tape dimensions, SDAT cannot record at the same density as the existing RDAT. It cannot deliver enough bandwidth to support recording a full two channel, 16-bit digital signal at the 48KHz or 44.1KHz sampling rates currently in use for digital audio. Instead, the format performs sophisticated data compression on the signal, in essence, throwing away those parts of the signal that are psychoacoustically inaudible. Thus, the format doesn't record the entire digital signal, but allegedly the only information lost is stuff you can't hear, anyway, so it doesn't matter. The same claim was made for the analog copy-protect signal notch when that was proposed, and testing by the NBS showed that the claim was false--the differences were trivially audible. I therefore remain a skeptic of Phillips's claims that their data compression doesn't affect the signal. I suspect that the golden ears, who already bash RDAT and CDs for their signal infidelity, are going to have a field day with SDAT. I'll take RDAT, thank you. |> How will the new Philips |>deck analog end stand up to normal tape players (the new dcc format |>I've heard will be able to play normal audio cassettes) What will |>the dynamic range be like? |> Shouldn't be much different from any other analog cassette player. I suspect they'll use the same head and other analog technology that they use in their current cassette players. --PSW
Janne.Anttila@lut.fi (Janne Anttila) (04/29/91)
RDAT is the existing DAT system. RDAT = Rotary head Digital Audio Tape.
Philips' DCC seems to be made for the record industry, not audiophiles,
since DCC-tapes can be copied faster and more easily than DAT-tapes.
The sound quality of DCC is likely to be clearly inferior to DAT due to
heavy data compression. I've seen a picture of a DCC-prototype, which
seemed to be built out of scrap (it had a mechanical tape counter!),
but commercial models have not been published yet.
I remember that Sony was developing a contact copy method for faster
DAT copying. I haven't heard of it lately, what's the situation?
--
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Janne Anttila /> ...mutta Saturnuksesta l{hestyy taivaanlaiva. />
/> Veljet, meid{n on syyt{ olla varuillamme, />
[{ni ylh{{lt{ /> sill{ Saturnuksen miehet eiv{t tunne armoa. />
_________________________________________________________________/>ted@dgbt.doc.ca (Ted Grusec) (04/29/91)
For an excellent overview of DCC (Philips), including elucidation of the PASC coding scheme, economics, subjective listener evaluation, etc., see the series of short articles in the April 91 Stereophile. I am doing subjective evaluations in experiments with a similar coding scheme (Musicam) in the digital audio broadcasting domain, and, I must say, the results are very impressive. Most listeners cannot tell the difference between an original CD and the PASC encoded version, even though the latter reduces the bit rate by a factor of 6! -- ========================================================================== Ted Grusec Communications Research Centre (Govt. of Canada, DOC) 3701 Carling Ave., Ottawa, Ont.K2H 8S2, CANADA Internet: ted@dgbt.doc.ca Compuserve: 73607,1576 (613) 998 2762 Fax (613) 993 8657
ggs@ulysses.att.com (Griff Smith) (04/30/91)
In article <11521@uwm.edu>, winalski@psw.enet.dec.com (Paul S. Winalski) writes: > In article <11436@uwm.edu>, > ... the format doesn't record the entire digital signal, but allegedly > the only information lost is stuff you can't hear, anyway, so it > doesn't matter. The same claim was made for the analog copy-protect > signal notch when that was proposed, and testing by the NBS showed that > the claim was false--the differences were trivially audible. It's not the same thing at all. The Phillips system probably deletes signals that are below perception thresholds, the copy-protect notch deleted a narrow bad unconditionally. > I therefore remain a skeptic of Phillips's claims that their data > compression doesn't affect the signal. No argument, the compression affects the signal. It would probably be unintelligible to a modem. > I suspect that the golden ears, who already bash RDAT and CDs for their > signal infidelity, are going to have a field day with SDAT. No argument here, either. I would paraphrase it as "the golden ears, who already imagine signal infidelity in RDAT and CD will have a field day". They will. They will also refuse to compare straight digital recordings with compressed recordings, which would confirm that the differences are usually inaudible. Instead, they will compare SDAT with LP and then point out the obvious sonic clarity of the latter. If they do compare SDAT with CD, they will refuse to do proper level matching because the extra components needed to balance the output levels might obscure the clarity of the superior medium. > I'll take RDAT, thank you. I'll admit to a nagging feeling that I'd like to have the whole signal recorded, but it's not based on rational behavior. When serving as a test subject for hearing compressed digital sound, I was unable to select any of the compressed signals reliably. -- Griff Smith AT&T (Bell Laboratories), Murray Hill Phone: 1-908-582-7736 UUCP: {most AT&T sites}!ulysses!ggs Internet: ggs@ulysses.att.com
drm2@mvuxn.att.com (David R Moran) (04/30/91)
In article <11521@uwm.edu> winalski@psw.enet.dec.com (Paul S. Winalski) writes: >In article <11436@uwm.edu>, >km456265@longs.LANCE.ColoState.Edu (Kevin Melsheimer) writes: >|> >|>Has anyone heard any information about the new digital format that >|>is coming out sometime this summer? Is the new RDAT system supposed >|>to be as good as existing DAT systems? > >The new format is not RDAT (rotating-head DAT). It is SDAT (stationary-head >DAT). > >--PSW For whatever it's worth (not much in this forum, perhaps), I heard firsthand testimony from Boston Audio Society colleagues I respect in the January BAS meeting (a WCES wrapup) concerning tough auditioning tests of DCC (data-compressed SDAT). Peter Mitchell and Brad Meyer both said that so far as they could tell, using the most rigorous material (such as L-R low-level piano decay), Phillips had done their homework and their psychoacoustic testing of in-house subjects showing the greatest acuity extraordinarily well .... The system sounded superb, in other words -- that is, entirely neutral. I have not heard it myself, but Peter and Brad are not readily gulled. David Moran
lou@caber.valid.com (Louis K. Scheffer) (04/30/91)
Janne.Anttila@lut.fi (Janne Anttila) writes: >The sound quality of DCC is likely to be clearly inferior to DAT due to >heavy data compression. This is not clear one way or another. 16 bit linear encoding is not that great either. Suppose, for example, that you took 20 bit samples, and then applied data compression to them. The audible results would depend on whether you gained more from higher resolution samples than you lost from compression. I read that the Phillips system has more dynamic range than 16 bit linear coding, so there are at least _some_ things that are better with that scheme. Listening tests will be the only way to tell if the DCC scheme sounds better, worse, or the same as 16 bit linear. Until these are done the situation is unclear. There is one thing that is clear, however. People will complain about the compression, blaming it for all sorts of things. I think that for this reason alone Phillips should have a lossless coding mode. This could still save a factor of 2 or 3 in bits, but at no loss in accuracy. I suppose, however, that they wanted bigger compression factors. With lossless data compression, you could put 60 KHz, 20 bit samples on current CDs easily. Now that would be a good use of data compression! -Lou Scheffer-
sundinKC@dna.lth.se (Anders Sundin) (04/30/91)
Ted Grusec (ted@dgbt.doc.ca) writes: >For an excellent overview of DCC (Philips), including elucidation of >the PASC coding scheme, economics, subjective listener evaluation, >etc., see the series of short articles in the April 91 Stereophile. I >am doing subjective evaluations in experiments with a similar coding >scheme (Musicam) in the digital audio broadcasting domain, and, I must >say, the results are very impressive. Most listeners cannot tell the >difference between an original CD and the PASC encoded version, even >though the latter reduces the bit rate by a factor of 6! And then it deserves to be mentioned that PASC for DCC has uses twice as much data as MUSICAM for broadcasting. Philips has drawn (draws?) upon the experience from broadcasting tests to use all that extra data to further improve the already excellent performance of MUSICAM. This also makes the signal more robust for multiple generation decoding/encoding copying and people messing around wildly with the frequency response. A question: Is the "18-bit" resolution hardwired into the system or is it consequence of the resolution of the surrounding AD/DA converters? The latter seems most likely but I have seen no solid data. (Stereophile isn't imported to Sweden. How were the listening tests conducted, and what were the results?) Jonas Palm PS. I'm posting this from the account of a friend. Please don't hold him responsible. My own E-mail adress is: OK3JONAS@SELDC52.BITNET ok3jonas@gemini.ldc.se -- ------------------------------------------------------------- | Anders Sundin | e-mail: sundinKC@dna.lth.se | | University of Lund | ok2aps@gemini.ldc.lu.se | | Organic Chemistry 2, | ok2aps@seldc52.bitnet | | P.O. Box 124 | phone: +46 46 108214 | | S-22100 Lund, Sweden | fax: +46 46 108209 | -------------------------------------------------------------
bill%thd.tv.tek.com@RELAY.CS.NET (William K. McFadden) (05/02/91)
In article <11578@uwm.edu> ggs@ulysses.att.com (Griff Smith) writes: > >I'll admit to a nagging feeling that I'd like to have the whole signal >recorded, but it's not based on rational behavior. This isn't as irrational as you might think. The problem with the DCC compression scheme is that signal degradation occurs with each encoding. Since the process isn't complementary (e.g., lossless), even digital copying will introduce additional loss (unless it's copied in compressed form). Since the SPDIF digital interface uses PCM encoding, every digital copy will have to pass through another lossy decode/encode. After just a few generations, the artifacts may be audible. I think this is the real reason record companies like DCC. High speed duplication isn't that big of an issue these days. It's done with video tapes all the time. The inability to make perfect copies is what they really want. BTW, I have heard demos of MUSICAM and other compression schemes. They all sounded very good, certainly better than any analog noise reduction system I've heard. However, even my non-golden ears could hear artifacts. Solo castanets is the best test signal I've heard for exploiting the weaknesses of the systems. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill Phone: (503) 627-6920 "SCUD: Shoots Crooked, Usually Destroyed"
winalski@psw.enet.dec.com (Paul S. Winalski) (05/06/91)
In article <11685@uwm.edu>,
bill%thd.tv.tek.com@RELAY.CS.NET (William K. McFadden) writes that DCC will
require an encode/decode for each digital copy, with information loss at
each step.
Are DCC decks, then, only going to have SPDIF digital interfaces, which
have this signal loss property, or will there be another digital interface,
usable for DCC->DCC copies, that just sends over the encoded bits?
--PSWbill@thd.tv.TEK.COM (William K. McFadden) (05/09/91)
In article <11820@uwm.edu> winalski@psw.enet.dec.com (Paul S. Winalski) writes: >In article <11685@uwm.edu>, >bill%thd.tv.tek.com@RELAY.CS.NET (William K. McFadden) writes that DCC will >require an encode/decode for each digital copy, with information loss at >each step. > >Are DCC decks, then, only going to have SPDIF digital interfaces, which >have this signal loss property, or will there be another digital interface, >usable for DCC->DCC copies, that just sends over the encoded bits? As far as I know, they will only have the SPDIF connectors. Of course, given enough demand, the manufacturers might be willing to include a direct DCC-to-DCC mode for copying, but I wouldn't get my hopes up. Remember, DCC was designed to be a format for the masses. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 bill@tv.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill Phone: (503) 627-6920 "SCUD: Shoots Crooked, Usually Destroyed"