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What is "time resolution"?
Axon
post Oct 5 2006, 21:50
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So I've become involved in a rather colorful argument (I'm Publius in the thread) with somebody on stevehoffman.tv. The original thread revolved around shooting down an old audiophile canard, about how subsample delays cannot be represented in PCM. In the course of that debate, I've begun to question a couple things.
  • Is it ever accurate to use the term "time resolution" in any sort of technical context? To the best of my knowledge, it has no universally agreed upon technical definition. Most of the times I've seen it used are either for SACD/DVD-A marketing fluff, or to describe FFT window lengths. I'm tempted to just go quasi-logical-positivist on everybody and say that it is a completely meaningless phrase.
  • Is there any meaningful time-domain constraint on audio quality that is directly related to the sampling period? Subsample delays (as I've shown above) are not meaningfully related. Bandwidth is a frequency-domain attribute. Pre-echo potentially gets more audible at lower sampling rates, but this is not a concern with sigma-delta ADCs, and it is of debatable audibility at 44.1 to begin with. Some DSP operations may be harder to implement at lower sample rates, but most of the issues involve seem implementation-related. I'm suspecting that there are no clear general limits as to what can and cannot be accomplished in PCM, except with respect to very domain-specific or system-specific situations; and so any claims of 44khz always being limited in ways different from bandwidth may be regarded with skepticism.
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Woodinville
post Oct 5 2006, 23:20
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QUOTE (Axon @ Oct 5 2006, 13:50) *
So I've become involved in a rather colorful argument (I'm Publius in the thread) with somebody on stevehoffman.tv. The original thread revolved around shooting down an old audiophile canard, about how subsample delays cannot be represented in PCM. In the course of that debate, I've begun to question a couple things.
  • Is it ever accurate to use the term "time resolution" in any sort of technical context? To the best of my knowledge, it has no universally agreed upon technical definition. Most of the times I've seen it used are either for SACD/DVD-A marketing fluff, or to describe FFT window lengths. I'm tempted to just go quasi-logical-positivist on everybody and say that it is a completely meaningless phrase.
  • Is there any meaningful time-domain constraint on audio quality that is directly related to the sampling period? Subsample delays (as I've shown above) are not meaningfully related. Bandwidth is a frequency-domain attribute. Pre-echo potentially gets more audible at lower sampling rates, but this is not a concern with sigma-delta ADCs, and it is of debatable audibility at 44.1 to begin with. Some DSP operations may be harder to implement at lower sample rates, but most of the issues involve seem implementation-related. I'm suspecting that there are no clear general limits as to what can and cannot be accomplished in PCM, except with respect to very domain-specific or system-specific situations; and so any claims of 44khz always being limited in ways different from bandwidth may be regarded with skepticism.


Having read that thread, or some of it, it's clear that there are several issues being confuted by people who do not want to let go of their pet belief system.

The first issue is that of pure delay. You've killed that. You can point out that if you store the data in 16 bit signed, that yes, there is a limit, it's directly related to the sampling rate times the number of levels available for quantization... smile.gif i.e. directly related to the SNR and the sampling rate.

The second is that of jitter. You need to beat on these people to point out that jitter is different for each sample, and your time delay is not.

Time delay has been reported as audible down to 5 to 10 microseconds in binaural settings with a great deal of care and signal prep involved. No lower.

The cited nanosecods, etc, are just stuff and nonsense.

What you need to do with the jitter crowd is to point out that the spectrum of the jitter is the big deal.

You can have 1 part in 1000 (relative to sample period) if the jitter has only frequencies below 1 Hz.

You can hear much more than that if you have high frequency jitter, and a high frequency signal.

Looking onward, we see the twirp who insists that things have to be periodic in order for subsample resolution to work.

Perhaps he needs to be acquinted with both the Nyquist theorem and the fact that for all real signals, Fourier synthesis works.

I'm not going to get an ID to go argue with those guys. Blah.

This post has been edited by Woodinville: Oct 5 2006, 23:21


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Posts in this topic
- Axon   What is "time resolution"?   Oct 5 2006, 21:50
- - benski   Subsample delays are relatively easy to implement ...   Oct 5 2006, 22:04
- - Axon   Well, duh. I showed in that thread that 1/20,000 ...   Oct 5 2006, 22:19
- - krabapple   QUOTE (Axon @ Oct 5 2006, 16:50) So I...   Oct 5 2006, 22:28
- - Mike Giacomelli   QUOTE (Axon @ Oct 5 2006, 13:50) Is it ev...   Oct 5 2006, 22:57
- - ChiGung   Yo, that was me (felimid) QUOTE Is there any meani...   Oct 5 2006, 23:07
|- - Axon   QUOTE (ChiGung @ Oct 5 2006, 17:07) Yo, t...   Oct 6 2006, 00:11
|- - legg   AFAIK, time resolution is most commonly used to re...   Oct 6 2006, 00:28
- - Woodinville   QUOTE (Axon @ Oct 5 2006, 13:50) So I...   Oct 5 2006, 23:20
|- - ChiGung   QUOTE ("woodinville")The first issue is ...   Oct 6 2006, 00:46
|- - Mike Giacomelli   QUOTE (ChiGung @ Oct 5 2006, 16:46) QUOTE...   Oct 6 2006, 02:10
||- - ChiGung   QUOTE (Mike Giacomelli @ Oct 6 2006, 02:1...   Oct 6 2006, 04:30
||- - Mike Giacomelli   QUOTE (ChiGung @ Oct 5 2006, 20:30) QUOTE...   Oct 6 2006, 06:27
|- - krabapple   QUOTE (ChiGung @ Oct 5 2006, 19:46) QUOTE...   Oct 6 2006, 06:21
|- - Woodinville   QUOTE (ChiGung @ Oct 5 2006, 16:46) Howev...   Oct 6 2006, 08:26
- - Woodinville   Well, considered for Guassian vs. Gaussian, dt * ...   Oct 6 2006, 00:35
- - kjoonlee   Does "higher sampling rates mean higher tempo...   Oct 6 2006, 00:47
|- - ChiGung   QUOTE (kjoonlee @ Oct 6 2006, 00:47) Does...   Oct 6 2006, 00:57
|- - kwwong   QUOTE (ChiGung @ Oct 5 2006, 18:57) QUOTE...   Oct 7 2006, 05:12
- - 2Bdecided   ChiGung, You can prove sub-sample time domain acc...   Oct 6 2006, 10:30
|- - ChiGung   QUOTE We're assuming the signal is band limite...   Oct 6 2006, 16:32
|- - krabapple   QUOTE (ChiGung @ Oct 6 2006, 11:32) I can...   Oct 6 2006, 16:54
||- - ChiGung   QUOTE But perhaps for starters, you can describe i...   Oct 6 2006, 17:08
||- - krabapple   QUOTE (ChiGung @ Oct 6 2006, 12:08) QUOTE...   Oct 6 2006, 21:11
||- - MedO   QUOTE (ChiGung @ Oct 6 2006, 18:08) Look....   Oct 7 2006, 10:43
|- - Mike Giacomelli   QUOTE (ChiGung @ Oct 6 2006, 08:32) QUOTE...   Oct 6 2006, 20:54
- - Axon   Okay, so this has gone completely f*cking off topi...   Oct 6 2006, 17:49
|- - krabapple   QUOTE (Axon @ Oct 6 2006, 12:49) Okay, so...   Oct 6 2006, 20:51
- - Canar   QUOTE Ask yourself: "is there any meaningful ...   Oct 6 2006, 21:20
- - Canar   Exactly, kwwong. ChiGung, consider this: In the co...   Oct 7 2006, 08:04
- - cabbagerat   QUOTE (MedO @ Oct 7 2006, 01:43) No, ther...   Oct 7 2006, 18:00
|- - MedO   QUOTE That assumption is a bit of a problem, in my...   Oct 7 2006, 18:42
- - cabbagerat   QUOTE (MedO @ Oct 7 2006, 09:42) Of cours...   Oct 7 2006, 20:57
|- - ChiGung   QUOTE (MedO @ Oct 7 2006, 09:42) Of cours...   Oct 7 2006, 23:18
|- - MedO   QUOTE (ChiGung @ Oct 8 2006, 00:18) the p...   Oct 8 2006, 00:13
|- - ChiGung   QUOTE (MedO @ Oct 8 2006, 00:13) QUOTE (C...   Oct 8 2006, 00:28
- - Canar   ChiGung, it is increasingly apparent you are not i...   Oct 8 2006, 00:26
- - Canar   I've provided a mathematical example of why yo...   Oct 8 2006, 01:05
- - cabbagerat   For your viewing pleasure, here's a quick demo...   Oct 8 2006, 08:07
|- - ChiGung   QUOTE (cabbagerat @ Oct 8 2006, 08:07) Fo...   Oct 8 2006, 15:02
- - Canar   So because sinc() interpolation is weird, PCM fail...   Oct 8 2006, 15:28
- - cabbagerat   QUOTE (ChiGung @ Oct 8 2006, 06:02) This ...   Oct 8 2006, 15:51
|- - ChiGung   QUOTE (cabbagerat @ Oct 8 2006, 15:51) I ...   Oct 8 2006, 16:10
- - KikeG   As others have said, time resolution of PCM is the...   Oct 8 2006, 17:59
|- - ChiGung   QUOTE (KikeG @ Oct 8 2006, 17:59) As othe...   Oct 8 2006, 18:14
|- - KikeG   QUOTE (ChiGung @ Oct 8 2006, 18:14) So yo...   Oct 8 2006, 18:24
||- - ChiGung   QUOTE (KikeG @ Oct 8 2006, 18:24) Resolut...   Oct 8 2006, 18:55
|- - Woodinville   QUOTE (ChiGung @ Oct 8 2006, 10:14) So yo...   Oct 8 2006, 19:37
|- - ChiGung   QUOTE (Woodinville @ Oct 8 2006, 19:37) Y...   Oct 8 2006, 19:57
|- - Woodinville   QUOTE (ChiGung @ Oct 8 2006, 11:57) Yeah ...   Oct 9 2006, 18:00
- - Canar   ChiGung, despite your frequent reassertions to the...   Oct 8 2006, 20:08
|- - ChiGung   QUOTE (Canar @ Oct 8 2006, 20:08) I would...   Oct 8 2006, 20:28
|- - ChiGung   I think that it is being claimed, almost unanimous...   Oct 8 2006, 21:44
|- - legg   QUOTE (ChiGung @ Oct 8 2006, 15:44) I hav...   Oct 9 2006, 01:32
||- - ChiGung   QUOTE (legg @ Oct 9 2006, 01:32) QUOTE (C...   Oct 9 2006, 02:16
|- - 2Bdecided   QUOTE (ChiGung @ Oct 8 2006, 21:44) The e...   Oct 9 2006, 15:08
- - legg   Fine forget about the code and do try to provide m...   Oct 9 2006, 03:27
|- - MedO   If I understand you right, you are saying that the...   Oct 9 2006, 09:35
|- - ChiGung   Hello all, I left this discussion in a tizz and ha...   Nov 15 2006, 01:16
|- - kwwong   QUOTE (ChiGung @ Nov 14 2006, 19:16) 44kH...   Nov 15 2006, 09:50
|- - kwwong   QUOTE (kwwong @ Nov 15 2006, 03:50) QUOTE...   Nov 16 2006, 10:24
- - 2Bdecided   Here are some nice pictures... I worked at 16-b...   Oct 9 2006, 15:24
- - cabbagerat   QUOTE (2Bdecided @ Oct 9 2006, 06:08) It...   Oct 9 2006, 16:54
- - Axon   So I was mainly pissed off in my earlier post beca...   Oct 9 2006, 17:30
|- - Woodinville   QUOTE (Axon @ Oct 9 2006, 09:30) The form...   Oct 9 2006, 18:41
- - 2Bdecided   ChiGung, Your experiment wouldn't work. By kn...   Nov 15 2006, 13:00
|- - ChiGung   QUOTE (2Bdecided @ Nov 15 2006, 12:00) .....   Nov 15 2006, 13:45
- - 2Bdecided   So, in short, you want to run an experiment to see...   Nov 15 2006, 14:29
|- - ChiGung   QUOTE (2Bdecided @ Nov 15 2006, 13:29) So...   Nov 15 2006, 14:45
|- - Woodinville   QUOTE (ChiGung @ Nov 15 2006, 05:45) QUOT...   Nov 15 2006, 19:42
|- - ChiGung   QUOTE (Woodinville @ Nov 15 2006, 18:39) ...   Nov 15 2006, 19:56
||- - Woodinville   QUOTE (ChiGung @ Nov 15 2006, 10:56) Nice...   Nov 15 2006, 20:01
||- - ChiGung   QUOTE (Woodinville @ Nov 15 2006, 19:01) ...   Nov 15 2006, 20:30
||- - AstralStorm   QUOTE (ChiGung @ Nov 15 2006, 20:30) It i...   Nov 15 2006, 22:43
||- - 2Bdecided   QUOTE (ChiGung @ Nov 15 2006, 20:30) Im f...   Nov 16 2006, 14:22
||- - ChiGung   QUOTE (2Bdecided @ Nov 16 2006, 13:22) My...   Nov 16 2006, 17:10
||- - SebastianG   QUOTE (ChiGung @ Nov 16 2006, 17:10) The ...   Nov 16 2006, 18:22
||- - ChiGung   QUOTE (SebastianG @ Nov 16 2006, 17:22) Q...   Nov 16 2006, 18:51
||- - Woodinville   QUOTE (ChiGung @ Nov 16 2006, 09:51) I be...   Nov 16 2006, 22:48
||- - ChiGung   QUOTE (Woodinville @ Nov 16 2006, 21:48) ...   Nov 16 2006, 23:32
||- - Woodinville   QUOTE (ChiGung @ Nov 16 2006, 14:32) ...   Nov 16 2006, 23:44
||- - ChiGung   QUOTE (Woodinville @ Nov 16 2006, 22:44) ...   Nov 17 2006, 00:15
|- - ChiGung   QUOTE (Woodinville @ Nov 15 2006, 18:42) ...   Nov 15 2006, 20:14
|- - Garf   QUOTE (ChiGung @ Nov 15 2006, 20:14) The ...   Nov 15 2006, 20:18
|- - Woodinville   QUOTE (ChiGung @ Nov 15 2006, 11:14) Im n...   Nov 15 2006, 23:35
|- - ChiGung   QUOTE (Woodinville @ Nov 15 2006, 22:35) ...   Nov 16 2006, 01:20
- - cabbagerat   QUOTE (ChiGung @ Nov 15 2006, 05:45) It i...   Nov 15 2006, 15:22
|- - ChiGung   QUOTE (cabbagerat @ Nov 15 2006, 14:22) T...   Nov 15 2006, 15:51
- - 2Bdecided   I wish you understood the theory CG, because witho...   Nov 15 2006, 16:18
|- - ChiGung   QUOTE (2Bdecided @ Nov 15 2006, 15:18) It...   Nov 15 2006, 17:01
|- - 2Bdecided   QUOTE (ChiGung @ Nov 15 2006, 17:01) QUOT...   Nov 15 2006, 18:06
|- - ChiGung   QUOTE (2Bdecided @ Nov 15 2006, 17:06) Yo...   Nov 15 2006, 18:31
- - SebastianG   I also don't see the point in checking the pos...   Nov 15 2006, 16:48
|- - ChiGung   QUOTE (SebastianG @ Nov 15 2006, 15:48) I...   Nov 15 2006, 17:16
- - SebastianG   I happened to code a subpixel detector for "x...   Nov 15 2006, 17:30
|- - ChiGung   QUOTE (SebastianG @ Nov 15 2006, 16:30) I...   Nov 15 2006, 17:53
|- - SebastianG   QUOTE (ChiGung @ Nov 15 2006, 17:53) It w...   Nov 15 2006, 17:59
|- - ChiGung   QUOTE (SebastianG @ Nov 15 2006, 16:59) Q...   Nov 15 2006, 18:21
- - MoSPDude   I've been trying to follow this as well, and e...   Nov 17 2006, 00:21
- - Woodinville   QUOTE (MoSPDude @ Nov 16 2006, 15:21) If ...   Nov 17 2006, 00:40
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