What's the use of a 192 kHz sample rate?
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From: Eric Jacobsen on 7 May 2008 13:26 On Wed, 07 May 2008 13:08:31 -0400, Jerry Avins <jya(a)ieee.org> wrote: >Don Pearce wrote: > > ... > >> What you don't do is send the packet twice, just in case there might >> be an error. > >How about three times, so the receiver can vote? :-) > >Jerry Sending packets twice also allows, at a minimum, Chase combining in order to exploit the time diversity. (I couldn't find the original post so maybe I'm making an erroneous assumption about the context.) Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
From: Randy Yates on 7 May 2008 13:33 Eric Jacobsen <eric.jacobsen(a)ieee.org> writes: > On Mon, 5 May 2008 05:54:09 -0700 (PDT), > dpierce.cartchunk.org(a)gmail.com wrote: > >>On May 5, 8:34 am, rajesh <getrajes...(a)gmail.com> wrote: >>> On May 5, 5:26 pm, Randy Yates <ya...(a)ieee.org> wrote: >>>> But yes, just doing a single repeat (transmitting two >>>> samples for every one) does not buy you anything. >>> >>> 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. >> >>You've invoked Shannon. How about going and actually >>READING and UNDERSTANDING it not? > > If I understand the argument correctly, there can be an advantage to > repeating samples or symbols or whatever you want to call them. > Repetition coding isn't very efficient, but it does have gain. > Likewise, transmitting something, anything, twice provides time > diversity in the receiver or, at a minimum, averaging in order to > improve SNR. It depends on your hardware, doesn't it? For example, if you had access to the actual photodetector output for each bit, you've essentially got soft decision information and chase combining (for two symbols) will help. However, if the laser receiver mechanism makes a hard decision in hardware, this type of combining won't help. Is this not correct? -- % Randy Yates % "So now it's getting late, %% Fuquay-Varina, NC % and those who hesitate %%% 919-577-9882 % got no one..." %%%% <yates(a)ieee.org> % 'Waterfall', *Face The Music*, ELO http://www.digitalsignallabs.com
From: Steven Sullivan on 7 May 2008 13:41 In rec.audio.tech Green Xenon [Radium] <glucegen1(a)excite.com> wrote: > Hi: > Why does DVD-Audio use 192 kHz sample rate? What's the advantage over > 44.1 kHz? Humans can't hear the full range of a 192 kHz sample rate? > On average, what is the minimum sample rate for a guy in his early to > mid 20s who likes treble? > I agree there are a small percentage of humans who can hear above 20 > kHz. However, DVD-audio uses a sample-rate of 192 kHz which allows a > maximum frequency of 96 kHz. There is no known case of any human being > able to hear sounds nearly as high as 96 kHz. I can agree with 48 kHz > sample rate and even 96 kHz sample-rate [maybe], but 192 kHz is just stupid. True, but by no means all DVD-Audio uses 192 kHz. Many use 96kHz...which arguably is also 'stupid'. -- -S maybe they wanna rock. maybe they need to rock. Maybe it's for the money? But That's none of our business..our business as fans is to rock with them.
From: Steven Sullivan on 7 May 2008 13:43 In rec.audio.tech Dave Platt <dplatt(a)radagast.org> wrote: > In article <481becfe$0$5141$4c368faf(a)roadrunner.com>, > Green Xenon [Radium] <glucegen1(a)excite.com> wrote: > >Hi: > > > >Why does DVD-Audio use 192 kHz sample rate? What's the advantage over > >44.1 kHz? Humans can't hear the full range of a 192 kHz sample rate? > > > >On average, what is the minimum sample rate for a guy in his early to > >mid 20s who likes treble? > In my personal opinion, a rate of 192 kilosamples/second (allowing a > passband of DC to 96 kHz) is indeed overkill as an audio delivery > standard. > There may be _some_ justification for it, as it eliminates the need to > place the knee of the anti-aliasing filter anywhere near the range of > frequencies that one _can_ hear. One of the criticisms made against > CD is that the sharp filtering which must be done at around 20 kHz can > cause artifacts which may be audible to some listeners, either due to > "pre-ringing" (with a symmetric FIR low-lass filter) or a frequency- > dependent delay and "smearing" of transients (with an IIR filter). > These effects can be moved up to higher frequencies, and prevented > from having effects in the human hearing passband, by increasing the > sampling rate. > My own personal guess is that a rate of 96 ksamples/second is probably > high enough to move any phase-affecting artifacts up well out of the > human hearing range, and that there are few if any benefits to going > to a rate higher than this. Dan Lavry and others have estimated that you're already in to the 'theoretical benefit zone' by 60 kHz. So if one feels the need for that, seems to me 88.2 kHz is the most sensible common choice. -- -S maybe they wanna rock. maybe they need to rock. Maybe it's for the money? But That's none of our business..our business as fans is to rock with them.
From: Steven Sullivan on 7 May 2008 13:47
In rec.audio.tech rickman <gnuarm(a)gmail.com> wrote: > On May 3, 3:28 am, Randy Yates <ya...(a)ieee.org> wrote: > > rickman <gnu...(a)gmail.com> writes: > > > If it really is a waste of time and money to use 192 kHz ADC and DAC, > > > why do you think they would do it? > > > > Greed. They think that the general public is dumb enough to buy into > > the lie that they really need such a system and would then spend lots of > > money repurchasing what they already have. > I'm curious, how do you know what unnamed people are thinking? My > understanding is that regardless of what frequencies acoustic testing > says that people can hear, audiophiles can hear the difference between > many of these "wasteful" features and otherwise adequate audio > systems. > I have known people who worked on professional equipment. The > extremes that they have design in are all audible to the buyers of > such systems. And people will judge wine's quality on the basis of its price. > I am not going to try to tell someone else what they can and can't > hear. Do you need to be told the conditions that might confuse you into thinking you heard a difference, when you didn't? -- -S maybe they wanna rock. maybe they need to rock. Maybe it's for the money? But That's none of our business..our business as fans is to rock with them. |