brad@kontron.UUCP (Brad Yearwood) (02/24/86)
There has been some discussion recently about digital audio tape formats,
and about how sampling rates are being made purposely incompatible with
the Compact Disc standard, presumably to prevent verbatim high-quality
copying. This raises a question - what techniques could one use to
implement a clean conversion from one sample rate to another - either
upward or downward, without converting back to analog and then re-digitizing
at the other rate?
Intuitively, I can more-or-less grasp the use of an FIR digital filter to
interpolate in the Philips 4x "oversampling" CD playback filter system. What
happens if you are not resampling to a convenient integer multiple of the
original rate? Would a similar technique be applicable for increasing
or decreasing the sampling by non-integer factors? Resampling to a decreased
rate is particularly baffling.
I suspect that the problem is similar (and a dimension simpler)
to conversion of television signals from one standard to another or
image magnification/shrinking. If anyone is familiar with literature
relevant to any of these areas, I would appreciate some pointers.
Brad Yearwood
Kontron Electronics {voder, pyramid, loral}!kontron!brad
Mountain View, CAben@catnip.UUCP (Bennett Broder) (02/26/86)
In article <531@kontron.UUCP>, brad@kontron.UUCP (Brad Yearwood) writes: > There has been some discussion recently about digital audio tape formats, > and about how sampling rates are being made purposely incompatible with > the Compact Disc standard, presumably to prevent verbatim high-quality > copying. This raises a question - what techniques could one use to > implement a clean conversion from one sample rate to another - either > upward or downward, without converting back to analog and then re-digitizing > at the other rate? > If anyone is familiar with literature > relevant to any of these areas, I would appreciate some pointers. This is a very real concern faced by record companies today. Many of the best digital tape recorders available operate at a higher sampling rate than used on CDs (e.g., the Soundstream at ~50k samples/sec). Last I heard, the only digital recorder to operate at 44.1 is the Sony PCM 1610, which has a reputation for mediocre analog electronics. What I am leading up to is, this problem has been solved using a commercial device called (of all things), a sampling rate converter. According to Telarc (who uses this device on almost all their CDs), this transformation occurs *completely* in the digital domain. The device Telarc uses is made by Studer/Revox (1425 Elm Hill Pike, Nashville, Tenn 37210). I don't know how helpful the folks at Studer would be, but if they were willing to sell you a service manual, send you literature, or just chat on the phone, you could probably get a handle on how the thing works. -- Ben Broder {ihnp4,decvax} !hjuxa!catnip!ben
atoy@watnot.UUCP (Andy Toy) (03/01/86)
In article <241@catnip.UUCP> ben@catnip.UUCP (Bennett Broder) writes: >What I am leading up to is, this problem has been solved using a commercial >device called (of all things), a sampling rate converter. According to >Telarc (who uses this device on almost all their CDs), this transformation >occurs *completely* in the digital domain. The device Telarc uses is made >by Studer/Revox (1425 Elm Hill Pike, Nashville, Tenn 37210). I don't know >how helpful the folks at Studer would be, but if they were willing to sell >you a service manual, send you literature, or just chat on the phone, you >could probably get a handle on how the thing works. You can also ask the folks at Sony since they sell a sampling rate converter also. Sorry, but I can't seem to locate the literature that I had from Sony where I read this. -- Andy Toy, Mapping Analysis and Design Group (MAD), Faculty of Environmental Studies, University of Waterloo, Waterloo, Ontario, CANADA N2L 3G1 (519) 885-1211 x6592 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= | UUCP: ...!watmath!watdcsu!atoy BITNET: atoy at watdcsu | # CSNET: atoy%watdcsu@waterloo.csnet CDN: atoy@dcsu.waterloo.cdn # | ARPA: atoy%watdcsu%waterloo.csnet@csnet-relay.arpa | =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
ron@brl-smoke.ARPA (Ron Natalie <ron>) (03/02/86)
> There has been some discussion recently about digital audio tape formats, > and about how sampling rates are being made purposely incompatible with > the Compact Disc standard, presumably to prevent verbatim high-quality > copying. This raises a question - what techniques could one use to > implement a clean conversion from one sample rate to another - either > upward or downward, without converting back to analog and then re-digitizing > at the other rate? Actually converting to analog won't necessarily help either. > Intuitively, I can more-or-less grasp the use of an FIR digital filter to > interpolate in the Philips 4x "oversampling" CD playback filter system. What > happens if you are not resampling to a convenient integer multiple of the > original rate? Would a similar technique be applicable for increasing > or decreasing the sampling by non-integer factors? Resampling to a decreased > rate is particularly baffling. You could use the least common multiple sample rate :->