jm@tekig.UUCP (Jeff Mizener) (12/03/84)
-------- In defense of my previous tirade, I refute the following: >The consumer standard may be fixed, but I am of the opinion, and some >other netters also, that a different and better professional standard >should be established. (sez Herb Chong) There are other "professional standards". The Audio Engineering Society has standardized on 48kHz for studio use, and 44.1kHz for "certain consumer applications". Some digital recorders available now digitize at 50kHz. A professional standard is not the problem; the problem is that the CONSUMER STANDARD is fixed. >Building a few conversion boxes for major record producers to go >"down to" the consumer standard isn't a problem. (Ibid.) OH YES IT IS! Unless you make certain assumptions... IF you sample at 50kHz and adequately bandlimit your input signal (read: music) so as to keep out of band signals below, say, 80-90dB, you do so for one (or both) of two reasons: first, because you feel that there is information above 18-20kHz. Second, because you want to ease the constraints on your anti-aliasing filter. Now you drop the sampling rate thru decimation. A filtering operation. Information will be lost. Maybe this is important, maybe not. The problem is that a better porfessional standard won't necessarily mean more information in the living room. If you sample at 44.1 to start with, you still lose information that is above 18-20kHz. You lose either way. The question is whether the information above 18-20kHz is important. Maybe yes, maybe no. Maybe the problems with CDs can be cured thru improved recording techniques, or by the use of dither in the player (see "Resolution below the least significant bit in digital audio systems with dither" by Vanderkooy and Lipshitz, JAES V32 #3 p106 March 1984 *). Perhaps the answer to the problem is in sampling at 176kHz, filtering down to 20kHz digitally and then decimating to 44.1kHz. I, for one, think at least part of the problem can be cured by fixing the wacko phase response of many if the commercial digital recorders. It doesn't become religion until you exhaust the facts. Jeff Mizener / Tektronix Portables ADG / Beaverton OR {ucbvax,decvax,purdue,uw-beaver,hplabs,allegra,ihnp4,ogcvax}!tektronix!tekadg!jm ARPA: tekadg!jm.tek@udel-relay CSnet: tekadg!jm@tek *PS To Herb Chong: Lipshitz and Vanderkooy are at U of Waterloo. Go see them for a good explaination.