IPB

Welcome Guest ( Log In | Register )

What is "time resolution"?
Axon
post Oct 5 2006, 21:50
Post #1





Group: Members (Donating)
Posts: 1984
Joined: 4-January 04
From: Austin, TX
Member No.: 10933



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.
Go to the top of the page
+Quote Post
 
Start new topic
Replies
cabbagerat
post Oct 7 2006, 20:57
Post #2





Group: Members
Posts: 1018
Joined: 27-September 03
From: Cape Town
Member No.: 9042



QUOTE (MedO @ Oct 7 2006, 09:42) *
Of course there is a limit. If there wasn't, you could store an infinite ammount of information in the exact position of that peak. Turning this the other way, you cannot store audio data in a way which completely preserves this information. However, the way it is it should be accurate enough. My point was that you can place your "brightness-peak" on a great number of positions between the pixels.
Well, I hadn't thought of it in the context of information storage, but that's a very nice way to visualize the limit. I would imagine that this is certainly not one of the limiting factors on the quality of digital storage, but there are certainly people who would say otherwise. You can't really pretend that any mechanical analog system (tape, vinyl, etc) could do better.


--------------------
Simulate your radar: http://www.brooker.co.za/fers/
Go to the top of the page
+Quote Post
ChiGung
post Oct 7 2006, 23:18
Post #3





Group: Members
Posts: 439
Joined: 9-February 05
From: county down
Member No.: 19713



QUOTE (MedO @ Oct 7 2006, 09:42) *
Of course there is a limit. If there wasn't, you could store an infinite ammount of information in the exact position of that peak. Turning this the other way, you cannot store audio data in a way which completely preserves this information. However, the way it is it should be accurate enough. My point was that you can place your "brightness-peak" on a great number of positions between the pixels.

What is 'accurate enough' is a different matter id not like to confuse the main investigation with.

The situation is, that the positioning of the brightness peak in the record is limited by the fact that the record has an implicit bandlimit. The position of the brightness peak in the source image is not implicity restricted by this limitation. (edit: yes the peak could be precisely positioned if we could employ all of the information stored in surrounding samples to do so - but all those other samples have information of their own to carry*) .

Depending on the characteristics of the information conveyable from the origional media (lenses, microphones, physics of air etc) it may be suitably restricted for precise capture/repoduction by certain samplerates, but because the source media may also not be suitably restricted (and very often is not) we have to allow for this possibility. It's surprised me that there has been a strong tendency to discount this as recognising source media may have finer resolution than target samplerates is fundamental to sensible statements of how accurately target samplerates can record the information of various sources.

Back to the 'peak of brightness', or 'peak of level' example (whichever is easier to visualise) The position of the peak in the source image or sound will in almost all cases be altered by the lowpass of conversion.
The record will then indicate a very precise position, but its disagreeance with the source will be unknown, the precise position of the peak in the source may be anywhere between the enclosing sample points

Then this makes clear my objection to stating the time resolution of PCM as near perfect. That the position in time of any time-localisable details, like peaks, attacks, cliffs etc, cannot be known to agree with the position of such details in the source, except when we can assume convienient limitations of the source. >A clause which basicaly passes on the limitations of the PCM record, to the source record. That is if we assume the source and the records limitations are the same, then to determine the accuracy limitations of the record, we must determine the limitations of the source. Only then can it be said that the record has no limitations with regards the assumable source. It becomes a confusingly convoluted case.

Another way of stating the case, is that the gaps between the samples, embody the unstateable frequencies above the implicit bandlimit. (By implicit bandlimit I mean to imply the one enforced by the nyquist frequency cuttoff, not arbitrary ones which may or may not have been applied on the record by extra conditioning)

Regarding the validity of the 'screen resolution' metaphor; when it was introduced earlier this reminder was made: -
QUOTE
(note that regardless of the quality of anyones particular video card system, bandlimited 'acoustic type' interpolation can be applied to visual data as well as audio (and is a rather good way to treat it, if not the optimal (?))


In other words it can be a fair, almost identical analogue, but if its not accessible to some, they may just have to try to skip over it.

Id remind again, that phase never indicates a point in time, it indicates conditions of a period located throughout time. So the fact that phase can be stated in a record quite precisely, does not mean any real position in time can be stated in the record as precisely.

Some are refering to limits of perceptability which are only discernable with physiological experimentation, limits of technical capability are not affected by what it is possible to hear or see.

Other queries have been raised all of which I hope the answers to will become clear, when the overall matter is realised shifty.gif

I exhibited some more underdog fatigue earlier blush.gif Im glad to see that did not harm anyones curiosity.

best regards'

...............
extras

This post has been edited by ChiGung: Oct 8 2006, 00:20


--------------------
no conscience > no custom
Go to the top of the page
+Quote Post

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
2 Pages V   1 2 >


Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 19th September 2014 - 23:44