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Audibility of Jitter, Proposing a series of tests
cabbagerat
post Dec 27 2006, 14:33
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The threshold of audibility of phase noise in ADC and DAC clocks is a fairly contentious issue in the HiFi and audiophile world. Some sources claim that jitter is clearly audible at low levels, and some claim that high levels of jitter are inaudible. The literature describes several tests, many with conflicting results.

One of the chief difficulties in testing the audibility of jitter is that it requires a complex hardware setup, which means that many listeners would be required to be present for an time consuming (and expensive) on site test. Over the last couple of months I have been thinking about organising a distributed listening test to look at the audibility of jitter in audio applications, based on algorithms for simulating the effects of jitter on signals. These algorithms are fairly well described in RF and telecomms engineering literature, and would be interesting for comparison purposes.

The kind of thing I have in mind is this:
Use samples which are accepted to sound good -> simulate jitter -> perform listening tests -> perform more tests at different levels of jitter depending on results

The purpose of this thread is to get ideas of the Hydrogenaudio community about performing these tests. Some of the things I would appreciate input on are:
  • Would such a test be useful
  • Would the results of such a test be valid?
  • What sort of test procedure would be best?


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krabapple
post Jan 13 2007, 04:32
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well, let me offer this 2005 paper for consideration, then


http://www.jstage.jst.go.jp/article/ast/26/1/50/_pdf


Audibility threshold for timing jitter, for 'golden eared' listeners in a two-alternative forced-choice paradigm using their preferred listening environment and samples: 250 ns.

This post has been edited by krabapple: Jan 13 2007, 04:36
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Eric Carroll
post Mar 3 2007, 07:07
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QUOTE (krabapple @ Jan 12 2007, 22:32) *
well, let me offer this 2005 paper for consideration, then...

Does anyone else have any additional actual published papers on this topic of the audibility of jitter or listening tests?

What journals cover this topic, if any?

My focus is to understand:
a) given a synthetic jitter profile, is it audible using DBT?
b) given a real jitter environment, is it audible using DBT?
c) can you DBT the difference between toslink and coax?

I have been looking into the basis of the audiophile belief that toslink is broken due to too much jitter and the implicit belief of the audibility of very small amounts of jitter. Given the intensity of the belief, perhaps where there is smoke, there is fire, even though this belief makes no sense to me based on my understanding of jitter and its impacts in this application space.

As far as I understand jitter impacts two things related to audio reproduction:
a) at the level of the synchronous bit transport, it influences bit error rates
b) at the level of the DAC, it causes errors in the recostruction of the waveform. The outcome of this is essentially higher noise and distortion, i.e. you just get a bump in the noise floor related to the waveform being reconstructed - its correlated to what is being reconstructed, which is a wrinkle - and possibly spectral aliases being created.

Detailed studies of this understanding are also appreciated with actual waveforms & spectrum views. I also want to be clear I understand the techniques to dejitter a clock, including reclocking and most importantly, buffering. The issue is about impact, not about repair or avoidance.

I don't want any more audiophile "received wisdom" on the issue of jitter, I have received lots of that.

Two papers keep getting cited at me in this discussion. One is the 1992 Stereophile article on jitter, which had a rebuttal in the Audio Critic and is not my idea of peer reviewed journal article (but has massive audiophile traction). The other is a 1992 AES paper, Is the AESEBU Digital Audio Inteface Flawed?, 93rd AES Convention, San Francisco. Both of these seem somewhat, well, dated, to me.

The paper previously cited in this thread has actual audibility testing, and appears to set an audibility threshold of jitter of around 250ns.

Papers without audibility studies set the threashold far lower. For example, Dunn's 1992 AES paper claims an audibility threshold of an astonishing 20ps at 20 KHz, based on his 1991 paper "Considerations for Interfacing Digital Audio Equipment to the Standards AES3, AES5, AES11, Proceedings of the 10th International AES Conference, 1991" (paper not yet found online). As another data point, "A Digital Discourse, Dr. Malcolm Hawksford; HiFi News & Record Review Feb,April, June, Aug, 1990" claims a peak jitter threshold of 400ps (also cited by Stereophile). I have not found the actual article yet, just citations and quotes.

Is Dunn's audibility curve an analytic derivation, or an audibility study? Dunn's curve of audibility is widely quoted. Anyone have a copy of this paper?

Others cited, but not yet found (I hesitate to pay the $20 AES paper fee) include "Eric Benjamin and Benjamin Gannon, "Theoretical and Audible Effects of Jitter on Digital Audio Quality", Preprint 4826 of the 105th AES Convention, San Francisco, September 1998" and "The Effects of Sampling Clock Jitter on Nyquist Sampling Analog-to-Digital Converters, and on Oversampling Delta-Sigma ADCs, 87th Convention of the Audio Engineering Society, October, 1989" (also cited by Stereophile).

There appears to be tremendous discussion of jitter measurement, but little understanding of what it actually means. A lot of this appears to me to be very old work and at best analytic, not audability based. None of it considers modern techniques to break the end to end synchronous clocking paradigm although some of them hint at what is now common practice in the telecommunications & Internet space.

Journals that publish in this area or references to further studies would be welcome.

(Zster, thanks for the reference to the Lavry overview paper. It is a useful overview document to help explain the impact of jitter in a well written way, and review some of the more modern methods to dejitter signals.)

This post has been edited by Eric Carroll: Mar 3 2007, 09:15
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Kees de Visser
post Mar 3 2007, 12:34
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A small group of experts on this subject (some from this forum) is currently investigating the audibility of jitter.
The idea is to develop a jitter simulation application to enable testing (listening) without a low-jitter DAC.
Alternatively an ultra-low jitter DAC and ADC are available for DBT.
There's no strict time schedule for the project. I'll post updates in this thread.
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Posts in this topic
- cabbagerat   Audibility of Jitter   Dec 27 2006, 14:33
- - Gigapod   QUOTE (cabbagerat @ Dec 27 2006, 14:33) T...   Dec 27 2006, 16:27
|- - Arnold B. Krueger   QUOTE (Gigapod @ Dec 27 2006, 11:27) QUOT...   Sep 26 2013, 03:48
|- - stv014   Not sure if this is relevant here, but there is cu...   Sep 26 2013, 10:56
|- - Arnold B. Krueger   QUOTE (stv014 @ Sep 26 2013, 05:56) Not s...   Sep 26 2013, 12:35
|- - stv014   QUOTE (Arnold B. Krueger @ Sep 26 2013, 13...   Sep 27 2013, 10:53
- - dariju   There is a good article about jitter @ Digital Dom...   Dec 27 2006, 17:07
|- - Gigapod   QUOTE (dariju @ Dec 27 2006, 17:07) There...   Dec 27 2006, 17:35
|- - Zster   QUOTE (Gigapod @ Dec 27 2006, 18:35) QUOT...   Dec 28 2006, 11:31
|- - Gigapod   QUOTE (Zster @ Dec 28 2006, 11:31) ... He...   Dec 28 2006, 12:30
- - cabbagerat   QUOTE (Gigapod @ Dec 27 2006, 07:27) I wo...   Dec 27 2006, 17:28
|- - Gigapod   QUOTE (cabbagerat @ Dec 27 2006, 17:28) ....   Dec 27 2006, 18:03
- - Pio2001   QUOTE (cabbagerat @ Dec 27 2006, 14:33) W...   Dec 27 2006, 18:39
|- - Gigapod   QUOTE (Pio2001 @ Dec 27 2006, 18:39) ... ...   Dec 27 2006, 18:48
- - cabbagerat   QUOTE (Pio2001 @ Dec 27 2006, 09:39) The ...   Dec 27 2006, 19:04
|- - Gigapod   QUOTE (cabbagerat @ Dec 27 2006, 19:04) ....   Dec 27 2006, 19:25
- - cabbagerat   QUOTE (Gigapod @ Dec 28 2006, 03:30) Cabb...   Dec 28 2006, 20:56
|- - Gigapod   QUOTE (cabbagerat @ Dec 28 2006, 20:56) ....   Dec 29 2006, 04:37
- - wimms   Jitter matters only during slope of the signal. In...   Dec 29 2006, 16:00
|- - Gigapod   QUOTE (wimms @ Dec 29 2006, 16:00) ... C1...   Dec 29 2006, 16:34
- - cabbagerat   The second one of those paper is fascinating. It...   Dec 29 2006, 18:25
|- - krabapple   QUOTE (cabbagerat @ Dec 29 2006, 12:25) T...   Jan 13 2007, 00:11
|- - Gigapod   QUOTE (krabapple @ Jan 13 2007, 00:11) .....   Jan 13 2007, 00:30
- - krabapple   well, let me offer this 2005 paper for considerati...   Jan 13 2007, 04:32
|- - Woodinville   QUOTE (krabapple @ Jan 12 2007, 19:32) we...   Jan 13 2007, 08:30
||- - Kees de Visser   For the Dutch speaking and jitter interested reade...   Jan 13 2007, 18:36
|- - Eric Carroll   QUOTE (krabapple @ Jan 12 2007, 22:32) we...   Mar 3 2007, 07:07
||- - Kees de Visser   A small group of experts on this subject (some fro...   Mar 3 2007, 12:34
|||- - jlohl   QUOTE (Kees de Visser @ Mar 3 2007, 12:34...   Mar 4 2007, 10:14
||- - 2Bdecided   QUOTE (Eric Carroll @ Mar 3 2007, 06:07) ...   Mar 21 2007, 12:31
||- - udauda   Here's another study on the threshold of jitte...   Aug 14 2009, 22:12
||- - udauda   http://www.jstage.jst.go.jp/article/ast/26/1/50/_p...   Aug 14 2009, 22:45
||- - Arnold B. Krueger   QUOTE (udauda @ Aug 14 2009, 17:12) Here...   Aug 16 2009, 11:50
|- - DonnieW   QUOTE (krabapple @ Jan 12 2007, 22:32) we...   Mar 5 2007, 00:52
|- - Kees de Visser   QUOTE (DonnieW @ Mar 5 2007, 00:52) QUOTE...   Mar 5 2007, 07:00
- - DualIP   For tests, why not generate a simple program that ...   Jan 14 2007, 09:14
- - knutinh   Correlated jitter is probably worse than random ji...   Jan 14 2007, 17:59
- - cabbagerat   QUOTE (DualIP @ Jan 14 2007, 00:14) For t...   Jan 16 2007, 09:18
- - sthayashi   Is this the wrong place to ask "What IS Jitte...   Mar 4 2007, 11:32
|- - mcbear   QUOTE (sthayashi @ Mar 4 2007, 11:32) For...   Mar 21 2007, 11:05
- - hlloyge   Well, bumping the old thread - has the test been c...   Feb 9 2010, 19:21
- - John_Siau   QUOTE (udauda @ Aug 14 2009, 17:45) We ha...   May 24 2010, 16:25
- - pdq   John, the post that you quote refers specifically ...   May 24 2010, 16:57
|- - John_Siau   QUOTE (pdq @ May 24 2010, 11:57) John, th...   May 24 2010, 18:15
|- - John_Siau   QUOTE (John_Siau @ May 24 2010, 13:15) We...   May 24 2010, 20:48
|- - 2Bdecided   QUOTE (John_Siau @ May 24 2010, 20:48) Hi...   May 25 2010, 09:12
|- - Arnold B. Krueger   QUOTE (2Bdecided @ May 25 2010, 04:12) QU...   May 25 2010, 14:04
|- - John_Siau   QUOTE (Arnold B. Krueger @ May 25 2010, 09...   May 25 2010, 18:09
|- - Arnold B. Krueger   QUOTE (John_Siau @ May 25 2010, 13:09) Wh...   May 26 2010, 16:09
|- - Woodinville   QUOTE (Arnold B. Krueger @ May 26 2010, 08...   May 26 2010, 18:36
|- - Arnold B. Krueger   QUOTE (Woodinville @ May 26 2010, 13:36) ...   May 26 2010, 20:06
- - punkrockdude   I have not read everything but here is a test I di...   Oct 11 2012, 21:01
- - punkrockdude   What's your opinion on the difference in audib...   Oct 14 2012, 13:38
|- - Arnold B. Krueger   QUOTE (punkrockdude @ Oct 14 2012, 08:38)...   Oct 15 2012, 14:48
||- - punkrockdude   QUOTE (Arnold B. Krueger @ Oct 15 2012, 15...   Oct 22 2012, 19:49
||- - Arnold B. Krueger   QUOTE (punkrockdude @ Oct 22 2012, 14:49)...   Oct 22 2012, 20:34
||- - punkrockdude   QUOTE (Arnold B. Krueger @ Oct 22 2012, 21...   Oct 22 2012, 21:40
|- - 2Bdecided   QUOTE (punkrockdude @ Oct 14 2012, 13:38)...   Oct 23 2012, 11:14
|- - Arnold B. Krueger   QUOTE (2Bdecided @ Oct 23 2012, 06:14) QU...   Oct 23 2012, 13:41
|- - 2Bdecided   QUOTE (Arnold B. Krueger @ Oct 23 2012, 13...   Oct 23 2012, 17:22
|- - Arnold B. Krueger   QUOTE (2Bdecided @ Oct 23 2012, 12:22) QU...   Oct 23 2012, 20:12
|- - 2Bdecided   QUOTE (Arnold B. Krueger @ Oct 23 2012, 20...   Oct 24 2012, 10:02
- - punkrockdude   2Bdecided: Interesting about subsamples. So there ...   Oct 23 2012, 12:26
|- - Arnold B. Krueger   QUOTE (punkrockdude @ Oct 23 2012, 07:26)...   Oct 23 2012, 13:32
|- - 2Bdecided   QUOTE (punkrockdude @ Oct 23 2012, 12:26)...   Oct 23 2012, 17:21
|- - Kees de Visser   To illustrate the importance of sub-sample accurac...   Oct 23 2012, 18:21
- - dhromed   File 2 and 3 null out almost perfectly. Amplificat...   Oct 23 2012, 13:25
|- - pdq   QUOTE (dhromed @ Oct 23 2012, 08:25) 4 an...   Oct 23 2012, 16:16
|- - 2Bdecided   QUOTE (pdq @ Oct 23 2012, 16:16) QUOTE (d...   Oct 23 2012, 17:30
|- - pdq   QUOTE (2Bdecided @ Oct 23 2012, 12:30) QU...   Oct 23 2012, 18:53
- - krabapple   FWIW, here's a good faith attempt to supply ex...   Sep 24 2013, 17:52
|- - Arnold B. Krueger   QUOTE (krabapple @ Sep 24 2013, 12:52) FW...   Sep 26 2013, 03:31
|- - krabapple   QUOTE (Arnold B. Krueger @ Sep 25 2013, 22...   Sep 27 2013, 02:59
|- - Arnold B. Krueger   QUOTE (krabapple @ Sep 26 2013, 21:59) QU...   Sep 28 2013, 14:32
- - 2Bdecided   I think UltimateMusicSnob is becoming the new Guru...   Sep 27 2013, 13:04
- - Wombat   QUOTE (2Bdecided @ Sep 27 2013, 14:04) I ...   Sep 27 2013, 14:38
- - 2Bdecided   Don't joke, a similar thought had crossed my m...   Sep 27 2013, 17:35
- - Wombat   i already made up my mind when he described things...   Sep 27 2013, 19:46
- - greynol   It's difficult to describe the tonality of noi...   Sep 27 2013, 19:56


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