What's the use of a 192 kHz sample rate?
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From: Mr.T on 5 May 2008 10:20 "Robert Lacoste" <use-contact-at-www-alciom-com-for-email> wrote in message news:481f044b$0$864$ba4acef3(a)news.orange.fr... > >Oversampled conversion does not require one to *store* information at > >the oversampled rate. > > Fully right, but it is a low cost solution if you want to avoid the cost of > a digital low pass filter & decimator... No, it's a very tiny one off cost Vs more expensive data storage. The solution that uses less expensive disk manufacture is the true "low cost solution". MrT.
From: rickman on 5 May 2008 10:39 On May 5, 3:04 am, nos...(a)nospam.com (Don Pearce) wrote: > On Sun, 4 May 2008 19:54:57 -0700 (PDT), rickman <gnu...(a)gmail.com> > wrote: > > >I am not an RF guy and the figure I actually remember was 150 dB. I > >hedged it a bit as 150 sounded rather extreme to me. I dunno if 150 > >is anything outside of ordinary or not. > > OK 150 - different bandwidth, then. The basic thermal noise at the > front end of a receiver is -174dBm + 10 log(bandwidth) + noise figure. > A noise or interference level that desensitizes that by 1dB will be > about 10dB lower than that level. You need to do the know the > bandwidth and noise figure to know the significance. > > What is significant is that this receiver has a desensitization limit > for interference that it throws at itself. I have never, ever come > across that before - it is always an external spec; you design the > internals so it doesn't interfere. I have *never* seen a commercial receiver that did not generated self interference. They normally are much more concerned with cost and are willing to live with a few spurs of noise in the spectrum. > >When you say that it costs too much to go around the design cycle many > >times, you clearly don't know much about the military procurement > >process. On the last radio that they built while I was there, they > >were up to rev 14 of the board that had nothing but the UI controller > >and external interfaces. You need to remember that often the > >development process is cost plus and the customer is *asking* for > >tough specs. It is only when they can't be delivered that they back > >off. > > Iteration 14 and the company was still in business? Anyone can afford > to do it again if they can't do it right. Was this a "cost-plus" > contract? Three or perhaps four was more the number I had in mind. You still don't understand the government procurement process. The company doesn't pay for this stuff. The government pays for development as well as the product. That is one of the reasons that I don't work there anymore. I have a strong drive to get it right the first time, literally. But the politics meant that anyone in the company could raise a stink about any silly imagined potential problem and I would get pressure to change the design, *after* the board was built. > >What is really funny is that you are getting wrapped around the axle > >about my use of this figure when that was really just an aside to an > >aside of my original point. Funny how these discussions get so far > >off topic. > > If you like. It was clearly a number you threw in because it sounded > impressively big, even though you hadn't a clue what it meant. You don't have to be insulting. I may not know RF by chapter and verse, but I have a feel for the issues. I remember very clearly the issue that was being discussed when I was given that number, I just don't remember the units. Lets face it, we all talk about dB in context and know exactly what is meant. But at some point *which* dB is being discussed can be forgotten. I still get mixed up when figuring dB in phone lines, but when I have to I can go back to references and figure out exactly what is correct. > >Did you read my post which used the original 140 dB figure? > > Yes. It was nonsense. Then why are you bothering to discuss this with someone who posts nonsense? Are you compulsive-obsessive? You are still discussing an issue that has nothing to do with the original point. Do you want to discuss the original point or are you just going to harp on this one tiny detail?
From: Jerry Avins on 5 May 2008 11:03 rajesh wrote: > On May 5, 6:15 pm, Jerry Avins <j...(a)ieee.org> wrote: >> Don Pearce wrote: >>> On Mon, 5 May 2008 04:36:01 -0700 (PDT), rajesh >>> <getrajes...(a)gmail.com> wrote: >>>> On May 5, 4:21 pm, nos...(a)nospam.com (Don Pearce) wrote: >>>>> On Mon, 5 May 2008 04:15:59 -0700 (PDT), rajesh >>>>> <getrajes...(a)gmail.com> wrote: >>>>>> On May 5, 3:46 pm, dpierce.cartchunk....(a)gmail.com wrote: >>>>>>> On May 5, 4:05 am, rajesh <getrajes...(a)gmail.com> wrote: >>>>>>>> Remember the shannon's theorem which places a >>>>>>>> trade off between error correcting codes and bandwidth. >>>>>>> Again, pure nonsense. Shannon's theorem >>>>>>> never discusses error correcting codes AT ALL. >>>>>> hi pierce , >>>>>> BTW from which school did u learn DSP? >>>>> Rajesh, please take some advice and don't do this. He is going to rip >>>>> you to pieces and embarrass you badly. >>>>> d >>>>> -- >>>>> Pearce Consultinghttp://www.pearce.uk.com >>>> Here is the coz for mis interpretation of my opinions. >>>> I am not comparing two different discs of two different capacities at >>>> all. >>>> I am comparing, given the same high capacity disc, which sampling rate >>>> can cope better with errors. >>>> And the answer is the one with which is oversampled. >>> Do you even know what oversampling is? You won't find it on any disc - >>> it is a function of the front end of an ADC. >>> And of course they are ALL oversampled, no exceptions, ever. >>>> say if u are comparing 44.1 kHz CD and a 196kHz DVD then they both >>>> cope with errors equally.there is no doubt about this. >>>> But then in the later case you are not comparing apples to apples. >>> The way they cope with errors is a function of the error >>> detection/correction schemes they use. >> And the packing density. If 192 samples are packed into the same space >> as 44.1, then a scratch of a particular size destroys more than 4 times >> as much data at the higher density. >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> �����������������������������������������������������������������������- Hide quoted text - >> >> - Show quoted text - > > I am talking about 44.1 kHz on the DVD, if a scratch occurs and if > 44.1*4.4 samples are lost > then it amounts to 4.4 sec loss in 44.1khz case and only 1 second in > 192 khz case. The DVD is packed more densely than the CD, so the same size scratch destroys more DVD than CD data. The time of the outage depends only in the size of the scratch and the playback peed of the disk. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Jerry Avins on 5 May 2008 11:05 rajesh wrote: > There is no gurantee that the audio signal is bandlimited. If we cant > percieve freq higher than 20k doesnt mean that they are not present No guarantee? We regularly use low-pass filters to guarantee that the signal is bandlimited. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: dpierce.cartchunk.org on 5 May 2008 13:25
On May 5, 9:44 am, rajesh <getrajes...(a)gmail.com> wrote: > On May 5, 5:54 pm, dpierce.cartchunk....(a)gmail.com wrote: > > > it does help the signal to get reconstructedl more accurately. > > > Not if the waveform is sampled at grater than 2 times the > > bandwidth, it does not. Once you sample greater than the > > Nyquist limit, NO extra information is gathered, not matter > > HOW much more your sample. The resulting output waveform > > is the same whether you sampled at 2..01times the bandwidth > > or 2000000 times the bandwidth. The output waveform DOES > > NOT get any more accurate. > > There is no gurantee that the audio signal is bandlimited. If we cant > percieve freq higher than 20k doesnt mean that they are not present This statement, all by itself, tells us you have no clue what you are talking about, and that your attempts to invoke Shannon are hollow. For proper sampling and reconstruction to occur, IT IS A PREREQUISITE THAT THE SIGNAL BANDWIDTH BE LIMITED TO LESS THAN 1/2 THE SAMPLE RATE. Any sampling system in this domain that does not follow this struct requirement IS BROKEN. Therefore, it can be taken as axiomatic, that once a signal has been sampled at faster than twice its bandwidth, sampling at even a higher rate WILL NOT gain you any accuracy in reconstruction. > > You've invoked Shannon. How about going and actually > > READING and UNDERSTANDING it not? > > i will do that But you already acted as if you had. Have you? |