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Hydrogenaudio Forum => Listening Tests => Topic started by: Arnold B. Krueger on 2014-06-20 01:02:59

Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-06-20 01:02:59
I prepared some files for people who want to do ABX tests related to jitter.

The file archive is here:

https://www.dropbox.com/sh/b35feharwc7doty/...t9KwuBTPbBa1JZa (https://www.dropbox.com/sh/b35feharwc7doty/AADTO9LPjXt9KwuBTPbBa1JZa)

Among other things it contains the following files:

no jitter.flac
30 Hz max jitter 0.1.flac
30 Hz Severe Jitter 0.05.flac
30 Hz jitter strong level .025.flac
30 Hz noticable jitter 0.0125.flac
30 Hz jitter marginal level .00625.flac
30 Hz threshold jitter 0.00312.flac

The intent that these files be ABXed using the FOOBAR2000 ABX comparator starting with the max jitter file.  The "max jitter" file is painfully easy to ace but is a good warm up. All but the last two files can be aced but at some point it will start taking a little work.

Allow about 7 minutes for listening to each of the first 4 files, about 12 minutes for the fifth one, and ??? for the remaining 2.

The files start out with a 1 KHz sine wave, with the same amount of jitter as the rest of the file. One can use FOOBAR2000 to select it or ignore it. You can FFT it to see how the jitter was applied.
Title: Jitter Listening test files
Post by: Thad E Ginathom on 2014-06-20 15:29:14
Thank you.

At this time, I'm more interested in the question what does jitter sound like anyway than in finding out any personal detection thresholds. Maybe that can come later

The world is full of people who talk about it and how much they have to spend to avoid it --- but they never play me any!
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-06-20 20:20:55
Thank you.

At this time, I'm more interested in the question what does jitter sound like anyway than in finding out any personal detection thresholds. Maybe that can come later

The world is full of people who talk about it and how much they have to spend to avoid it --- but they never play me any!



Then compare these two files:

no jitter.flac

30 Hz max jitter 0.1.flac

The audible difference is hard to miss, and is due to a real world kind of jitter that has been commonly found in AVRs that process HDMI A/V signals.
Title: Jitter Listening test files
Post by: mixminus1 on 2014-06-20 20:43:36
Thanks for these, Arnold.

What do the decimal numbers at the end of the file names correspond to?  I realize it's the relative amount of jitter, but can they be correlated with a measurement in picoseconds?
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-06-20 21:52:49
Thanks for these, Arnold.

What do the decimal numbers at the end of the file names correspond to?  I realize it's the relative amount of jitter, but can they be correlated with a measurement in picoseconds?


I don't like to reveal too much about the files because that may bias listeners.

What I can reveal up front is that:
1. The jitter in the "Max jitter" file will be audible to all,
2. The added jitter drops by about 50% between the files, and
3. The last two or three files will be difficult or impossible to distinguish from the "no jitter" file. 

Each file starts out with a 1 KHz test tone (that you can edit out of the listening test using FOOBAR's Set Start and Set End features) that a knowledgeable person can analyze with a FFT to determine the exact kind and amount of added jitter. All files were processed consistently across that file, so there is no "trust me" in this story.

It turns out that the current convention of measuring jitter in picoseconds is pretty meaningless because it is independent of the frequency of the test signal, while the audibility of jitter measured in picoseconds is dependent on the frequency of the test signal.

But I know what it is for the files, anyway.  The numbers are relevant to how the jitter was added to the files.
Title: Jitter Listening test files
Post by: mixminus1 on 2014-06-21 02:24:39
Fair enough - thanks for the info!
Title: Jitter Listening test files
Post by: MLXXX on 2014-12-09 11:18:29
ABK,
thanks for these jitter files. Here are my listening results, and comments:-

Maximum jitter file
I was able to ABX this very quickly against the nil jitter file:

foo_abx 1.3.4 report
foobar2000 v1.1.13
2014/12/09 18:45:02

File A: \\readyshare\usb_storage\jitter\30 Hz max jitter 0.1.flac
File B: \\readyshare\usb_storage\jitter\no  jitter.flac

18:45:02 : Test started.
18:45:51 : 01/01  50.0%
18:46:03 : 02/02  25.0%
18:46:12 : 03/03  12.5%
18:46:22 : 04/04  6.3%
18:46:32 : 05/05  3.1%
18:46:44 : 06/06  1.6%
18:46:49 : Test finished.

----------
Total: 6/6 (1.6%)


I heard a pervasive rasping quality to the 1kHz test tone, the guitar, and the vocal.

Threshold jitter level file
The jitter in the threshold jitter level file was too low for me to perceive it reliably, if at all.

Marginal jitter level file
The jitter in the marginal level jitter file was perceptible. It took me much longer to do this test, as I needed breaks to refresh my hearing:

foo_abx 1.3.4 report
foobar2000 v1.1.13
2014/12/09 19:04:35

File A: \\readyshare\usb_storage\jitter\30 Hz jitter marginal level .00625.flac
File B: \\readyshare\usb_storage\jitter\no  jitter.flac

19:04:35 : Test started.
19:07:03 : 01/01  50.0%
19:07:33 : 02/02  25.0%
19:15:59 : 03/03  12.5%
19:42:16 : 04/04  6.3%
20:03:51 : 05/05  3.1%
20:04:11 : Test finished.

----------
Total: 5/5 (3.1%)


I didn't find the 1kHz test tone much help in distinguishing the files at this relatively low level of jitter. I mostly used the last few seconds of the recording where the singer can be heard producing a somewhat unstable vibrato. She synchronises her pulsating vibrato with the beats of the music. For my ears, the vibrato sounds slightly more harmonious and "direct" in the nil jitter version. Also the guitar sounds slightly cleaner and less "woolly" in the nil jitter version. However there was very little in it for my ears.

Noticeable jitter level file
I found the jitter in this file a little distracting.

Strong jitter level file
I found the jitter level quite unpleasant. I would categorise this as an unacceptable level of jitter, even for casual listening.

Discussion
Have I heard this type of "jitter" sound before? No, not that I can recall. Not with any digital audio equipment over the years.

With the 1kHz test tone, the higher amplitude jitter reminded me of a very fast vibrato of a musical instrument.

What equipment did I use?  For preliminary testing I used a Xonar sound card and headphones. I was able to establish that the threshold level jitter file had too subtle an effect for me to be able to succeed with an ABX test. I then used a different pc* with onboard HDMI driving a low cost AVR.** (I was conscious of the irony of using an HDMI connection, in view of current discussion in the History and Accreditation of ABX Testing/Invention? thread starting at post #47 (http://www.hydrogenaud.io/forums/index.php?s=&showtopic=107540&view=findpost&p=883912).) Using the AVR fed from the pc, I could hear the effect of the artificially created jitter in the test files, either with headphones or loudspeakers.

It will be interesting if ABK is able to disclose for us what level of jitter was present in his "threshold jitter level file", and how that broadly compares with the performance of real world HDMI connected devices.

I note as a general comment that there is always the possibility of reducing jitter anyway in a playback device by use of a small buffer and a steady clock with a relatively slow time constant for fine adjustments to its clock rate, if there is any doubt about the short term timing stability of a stream of incoming digital audio. What extent of buffering is commonly in use I have no idea.

____________

* This pc has the old version of the foobar ABX plug-in. For tests demanding very careful listening, I appreciate being able to see my progressive results. The replacement foobar ABX plug-in under development, when I last checked, conceals progressive results when in formal test mode. I have lodged a request that there be an option to display progressive results.
** The AVR used was a Pioneer VSX-820.
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-09 13:37:57
It will be interesting if ABK is able to disclose for us what level of jitter was present in his "threshold jitter level file", and how that broadly compares with the performance of real world HDMI connected devices.


Thank you for your work and comments.

The presence of the 1 KHz tone makes the files self-disclosing.  Use your favorite FFT tool to look at the sidebands, and there you are.  In the case of this file the first set of sidebands are at +/- 30 Hz with amplitudes about 66 dB below the carrier.

More readings on the topic:

The scientific literature (example Zwicker and Fastl) suggests that FM distortion is heard based on three different perceptual models depending on jitter frequency. At very low jitter frequencies, the ear simply tracks the changes. LP rotation-based jitter is usually perceived this way. Above a few Hz jitter is heard as roughness which my 30 Hz jitter samples demonstrate quite clearly. Above a few 100 Hz masking starts coming into play.

Reference Zwicker and Fastl Psychoacoustics Facts and Models (Third Edition, 2007):

Zwicker and Fastel's Psychoacoustics Facts and Models PDF (http://www.autistici.org/2000-maniax/texts/Psychoacoustics%20-%20Facts%20And%20Models%20-%20Third%20Edition%20(Hugo%20Fastl).pdf)

Chapter 10, page 258 paragraph 10.1


Here is the information that inspired my choice of 30 Hz as my first test frequency

Straight from Amir's own tests! (http://amirviews.smugmug.com/photos/i-7wBmTvV/0/XL/i-7wBmTvV-XL.png)

(http://amirviews.smugmug.com/photos/i-7wBmTvV/0/XL/i-7wBmTvV-XL.png)

With the sideband frequencies annotated:

(http://www.avsforum.com/photopost/data/2374109/6/62/621aa066_pioneeravrj-test.png)

Please notice that the largest set of sidebands are at +/- 30 Hz, indicating a jitter frequency of 30 Hz.

The complaints from certain quarters over this choice of test frequencies seems to be in agreement with the old saw: "No good deed goes unpunished". I used the guy's own selected data as a guide and see what I get! ;-)

Here is an example of a digital audio produce with relatively high amounts of jitter:

(http://www.madronadigital.com/Library/AudioJitter.png)

As you can see the sidebands are about 80 dB down and are at +/- 3.0 Khz.

or here:

a fairly modern Onkyo TXNR 1009 AVR's HDMI jitter with all sidebands > 100 dB down (plenty fine).

http://2.bp.blogspot.com/-d5banBFYrqI/UmSY...HDMI+Jitter.png (http://2.bp.blogspot.com/-d5banBFYrqI/UmSYk2MsnzI/AAAAAAAACIs/bg9JnmwtZV8/s1600/ONKYO+HDMI+Jitter.png)

(http://2.bp.blogspot.com/-d5banBFYrqI/UmSYk2MsnzI/AAAAAAAACIs/bg9JnmwtZV8/s1600/ONKYO%20HDMI%20Jitter.png)

Or apparently the same AVR under what may be slightly different test conditions with the first sidebands +/- 120 Hz at about 90 dB down (still OK).

http://amirviews.smugmug.com/photos/i-tn5r...-tn5rJfr-X3.png (http://amirviews.smugmug.com/photos/i-tn5rJfr/0/X3/i-tn5rJfr-X3.png)

(http://amirviews.smugmug.com/photos/i-tn5rJfr/0/X3/i-tn5rJfr-X3.png)

Quote
I note as a general comment that there is always the possibility of reducing jitter anyway in a playback device by use of a small buffer and a steady clock with a relatively slow time constant for fine adjustments to its clock rate, if there is any doubt about the short term timing stability of a stream of incoming digital audio. What extent of buffering is commonly in use I have no idea.


Agreed. the actual jitter in any audio reconstructed from the digital domain is reducible to any desired level. My impression is that most modern designers are guided by influences similar to this paper "‘Theoretical and audible effects of jitter on digital audio quality,’’ Preprint of the 105th AES Convention, #4826 (1998).E. Benjamin and B. Gannon.

Engineers can reduce it arbitrarily but since arbitrarily large amounts of reduction tend to be arbitrarily expensive, they just put it well below what they expect and/or find it to be audible at.
Title: Jitter Listening test files
Post by: lithopsian on 2014-12-09 13:57:35
The files contain tags, including a title.  The title for the "threshold" file says "max"  I wasn't ABX'ing, just curious, and was most confused that I couldn't hear anything at all in the max file.  Because I was listening to the threshold case
Title: Jitter Listening test files
Post by: amirm on 2014-12-09 14:26:52
I note as a general comment that there is always the possibility of reducing jitter anyway in a playback device by use of a small buffer and a steady clock with a relatively slow time constant for fine adjustments to its clock rate, if there is any doubt about the short term timing stability of a stream of incoming digital audio. What extent of buffering is commonly in use I have no idea.

Buffering gets used in every device out there.  The problem with slow adjustment is the tracking range is very wide.  A receiver needs to lock onto sampling rates from 32 Khz to 192 Khz.  If it goes too slow, when you switch sources, you will have to wait many seconds for it to find and lock onto the incoming sample rate.  Customers will not accept input switching delays of more than 1 or 2 seconds whereas they are oblivious to jitter as a problem so fast switching wins.

Here is a high-resolution spectrum of jitter in a Pioneer AVR as measured by Paull Miller of HiFi news:

(http://amirviews.smugmug.com/photos/i-9QMffrp/0/X2/i-9QMffrp-X2.png)

Everything but the center tone are distortion/jitter sidebands.  We see tons of components there, not just one "30 Hz" frequency Arny has picked.  30 Hz is representative of what you hear in analog systems.  What governs its audibility at the very high levels is temporal masking.  The peak is 4 Khz so 30 Hz is not quite the peak but nevertheless, is not symptomatic of modern manifestation of jitter which can have arbitrary components. 

There are solutions to this but it requires design skills, and a few dollars worth of parts:

(http://amirviews.smugmug.com/photos/i-qbNMCxr/0/X2/i-qbNMCxr-X2.png)

At the other extreme we have these horrid measurements that I made of this $1000 premium AVR:

(http://amirviews.smugmug.com/photos/i-CKLfQn8/0/X2/i-CKLfQn8-X2.png)

As the graph indicates, these are the exact same measurements of the same device just a few seconds apart.  The AVR randomly induces tons more jitter into the DAC clock resulting in much increased low frequency random jitter and increase in correlated distortions.

This is just bad engineering taking advantage of customers not having any visibility into this performance aspect of device.  Video magazines don't measure jitter.  Audio magazines which do measure jitter don't care about AVRs.

Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-09 14:33:39
The files contain tags, including a title.  The title for the "threshold" file says "max"  I wasn't ABX'ing, just curious, and was most confused that I couldn't hear anything at all in the max file.  Because I was listening to the threshold case


I'll try to do better next set of files.  I may get some time to correct the tags in this set.
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-09 14:35:56
I note as a general comment that there is always the possibility of reducing jitter anyway in a playback device by use of a small buffer and a steady clock with a relatively slow time constant for fine adjustments to its clock rate, if there is any doubt about the short term timing stability of a stream of incoming digital audio. What extent of buffering is commonly in use I have no idea.

Buffering gets used in every device out there.  The problem with slow adjustment is the tracking range is very wide.  A receiver needs to lock onto sampling rates from 32 Khz to 192 Khz.  If it goes too slow, when you switch sources, you will have to wait many seconds for it to find and lock onto the incoming sample rate.  Customers will not accept input switching delays of more than 1 or 2 seconds whereas they are oblivious to jitter as a problem so fast switching wins.

Here is a high-resolution spectrum of jitter in a Pioneer AVR as measured by Paull Miller of HiFi news:

(http://amirviews.smugmug.com/photos/i-9QMffrp/0/X2/i-9QMffrp-X2.png)

Everything but the center tone are distortion/jitter sidebands.  We see tons of components there, not just one "30 Hz" frequency Arny has picked.  30 Hz is representative of what you hear in analog systems.  What governs its audibility at the very high levels is temporal masking.  The peak is 4 Khz so 30 Hz is not quite the peak but nevertheless, is not symptomatic of modern manifestation of jitter which can have arbitrary components. 

There are solutions to this but it requires design skills, and a few dollars worth of parts:

(http://amirviews.smugmug.com/photos/i-qbNMCxr/0/X2/i-qbNMCxr-X2.png)

At the other extreme we have these horrid measurements that I made of this $1000 premium AVR:

(http://amirviews.smugmug.com/photos/i-CKLfQn8/0/X2/i-CKLfQn8-X2.png)

As the graph indicates, these are the exact same measurements of the same device just a few seconds apart.  The AVR randomly induces tons more jitter into the DAC clock resulting in much increased low frequency random jitter and increase in correlated distortions.

This is just bad engineering taking advantage of customers not having any visibility into this performance aspect of device.  Video magazines don't measure jitter.  Audio magazines which do measure jitter don't care about AVRs.


Depends on whether you define bad engineering in terms of sound quality as heard by human beings listening to music and/or dialog or conformance with arbitrary numerical standards, no?
Title: Jitter Listening test files
Post by: lithopsian on 2014-12-09 14:40:58
The files contain tags, including a title.  The title for the "threshold" file says "max"  I wasn't ABX'ing, just curious, and was most confused that I couldn't hear anything at all in the max file.  Because I was listening to the threshold case


I'll try to do better next set of files.  I may get some time to correct the tags in this set.


No problem.  I think this is a great thread that sheds some light both on the jitter scaremongers and on those who claim it simply doesn't exist at detectable levels on modern audio systems.
Title: Jitter Listening test files
Post by: amirm on 2014-12-09 15:22:20
Posting these results here in addition to the parallel thread for others who only land here:
==============

http://www.avsforum.com/forum/91-audio-the...ml#post25081490 (http://www.avsforum.com/forum/91-audio-theory-setup-chat/1532092-debate-thread-scott-s-hi-res-audio-test-24.html#post25081490)

[quote author=Amir on AVS link=msg=0 date=]foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/06/18 16:39:16

File A: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\no jitter.wav
File B: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\30 Hz Severe Jitter 0.05.flac

16:39:16 : Test started.
16:39:52 : 01/01 50.0%
16:40:26 : 02/02 25.0%
16:40:38 : 03/03 12.5%
16:40:48 : 04/04 6.3%
16:40:58 : 05/05 3.1%
16:41:07 : 06/06 1.6%
16:41:24 : 07/07 0.8%
16:41:32 : 08/08 0.4%
16:41:51 : 09/09 0.2%
16:42:04 : 10/10 0.1%
16:42:12 : 11/11 0.0%
16:42:21 : 12/12 0.0%
16:42:43 : Test finished.

----------
Total: 12/12 (0.0%)

=============
foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/06/18 16:33:19

File A: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\30 Hz max jitter 0.1.flac
File B: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\no jitter.wav

16:33:19 : Test started.
16:34:25 : 01/01 50.0%
16:34:38 : 02/02 25.0%
16:34:58 : 03/03 12.5%
16:35:16 : 04/04 6.3%
16:35:26 : 05/05 3.1%
16:35:41 : 06/06 1.6%
16:35:54 : 07/07 0.8%
16:36:34 : 08/08 0.4%
16:36:44 : 09/09 0.2%
16:36:54 : 10/10 0.1%
16:37:03 : 11/11 0.0%
16:37:13 : 12/12 0.0%
16:38:05 : Test finished.

----------
Total: 12/12 (0.0%)

============

foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/06/18 16:44:39

File A: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\no jitter.wav
File B: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\30 Hz jitter strong level .025.flac

16:44:39 : Test started.
16:45:05 : 01/01 50.0%
16:45:15 : 02/02 25.0%
16:45:28 : 03/03 12.5%
16:45:36 : 04/04 6.3%
16:45:54 : 05/05 3.1%
16:46:17 : 06/06 1.6%
16:46:29 : 07/07 0.8%
16:46:45 : 08/08 0.4%
16:46:55 : 09/09 0.2%
16:47:05 : 10/10 0.1%
16:47:19 : 11/11 0.0%
16:47:33 : 12/12 0.0%
16:47:36 : Test finished.

----------
Total: 12/12 (0.0%)

=====

foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/06/18 19:04:40

File A: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\no jitter.wav
File B: C:\Users\Amir\Music\Arny's 30 Hz Jitter File\Arny's new files\30 Hz noticable jitter 0.0125.flac

19:04:40 : Test started.
19:05:27 : 01/01 50.0%
19:05:54 : 02/02 25.0%
19:06:19 : 03/03 12.5%
19:06:35 : 04/04 6.3%
19:06:57 : 05/05 3.1%
19:07:16 : 06/06 1.6%
19:07:43 : 07/07 0.8%
19:08:15 : 08/08 0.4%
19:08:37 : 09/09 0.2%
19:09:05 : 10/10 0.1%
19:09:30 : 11/11 0.0%
19:10:05 : 12/12 0.0%
19:10:09 : Test finished.

----------
Total: 12/12 (0.0%)[/quote]
Title: Jitter Listening test files
Post by: ajinfla on 2014-12-09 15:38:25
I think this is a great thread that sheds some light both on the jitter scaremongers and on those who claim it simply doesn't exist at detectable levels on modern audio systems.

Pardon me, but how would anything in this thread ever relate to whether jitter is audibly detectable in modern audio systems?
Is it fair to assume that modern audio systems are used...for music?
Further, it has been shown repeatedly that online ABX files are highly suspect and susceptible to the incorrigible with agendas.
i.e., they can be gamed for $pecific purpose.
When I see where someone has audibly detected jitter listening to music on a modern audio system, blind and supervised, I'll pay some attention.

cheers,

AJ
Title: Jitter Listening test files
Post by: lithopsian on 2014-12-09 16:10:17
I think this is a great thread that sheds some light both on the jitter scaremongers and on those who claim it simply doesn't exist at detectable levels on modern audio systems.

Pardon me, but how would anything in this thread ever relate to whether jitter is audibly detectable in modern audio systems?
Is it fair to assume that modern audio systems are used...for music?
Further, it has been shown repeatedly that online ABX files are highly suspect and susceptible to the incorrigible with agendas.
i.e., they can be gamed for $pecific purpose.
When I see where someone has audibly detected jitter listening to music on a modern audio system, blind and supervised, I'll pay some attention.

cheers,

AJ

And that's just what I mean: lots of noise with zero information content.  Simply your opinion that everything anyone says is crap.  Well this thread actually contains something that isn't crap and still you just complain.
Title: Jitter Listening test files
Post by: krabapple on 2014-12-09 19:14:50
ABK,
thanks for these jitter files. Here are my listening results, and comments:-

Maximum jitter file
I was able to ABX this very quickly against the nil jitter file:

foo_abx 1.3.4 report
foobar2000 v1.1.13
2014/12/09 18:45:02

File A: \\readyshare\usb_storage\jitter\30 Hz max jitter 0.1.flac
File B: \\readyshare\usb_storage\jitter\no  jitter.flac

18:45:02 : Test started.
18:45:51 : 01/01  50.0%
18:46:03 : 02/02  25.0%
18:46:12 : 03/03  12.5%
18:46:22 : 04/04  6.3%
18:46:32 : 05/05  3.1%
18:46:44 : 06/06  1.6%
18:46:49 : Test finished.

----------
Total: 6/6 (1.6%)


I heard a pervasive rasping quality to the 1kHz test tone, the guitar, and the vocal.

Threshold jitter level file
The jitter in the threshold jitter level file was too low for me to perceive it reliably, if at all.

Marginal jitter level file
The jitter in the marginal level jitter file was perceptible. It took me much longer to do this test, as I needed breaks to refresh my hearing:

foo_abx 1.3.4 report
foobar2000 v1.1.13
2014/12/09 19:04:35

File A: \\readyshare\usb_storage\jitter\30 Hz jitter marginal level .00625.flac
File B: \\readyshare\usb_storage\jitter\no  jitter.flac

19:04:35 : Test started.
19:07:03 : 01/01  50.0%
19:07:33 : 02/02  25.0%
19:15:59 : 03/03  12.5%
19:42:16 : 04/04  6.3%
20:03:51 : 05/05  3.1%
20:04:11 : Test finished.

----------
Total: 5/5 (3.1%)


I didn't find the 1kHz test tone much help in distinguishing the files at this relatively low level of jitter. I mostly used the last few seconds of the recording where the singer can be heard producing a somewhat unstable vibrato. She synchronises her pulsating vibrato with the beats of the music. For my ears, the vibrato sounds slightly more harmonious and "direct" in the nil jitter version. Also the guitar sounds slightly cleaner and less "woolly" in the nil jitter version. However there was very little in it for my ears.



Are you setting your trial number *before* you start your tests?

IOW, in the first results shown did you actually decide  beforehand, 'I will do 6 trials and stop'  and for second results shown , "I will do 5 and stop'?

If not, in the future  you should.

Certainly if you use progressive mode, where you can see your results as they happen, you should *not* stop at an arbitrary point....choose a number beforehand, and do the whole set.
Title: Jitter Listening test files
Post by: krabapple on 2014-12-09 19:24:03
No problem.  I think this is a great thread that sheds some light both on the jitter scaremongers and on those who claim it simply doesn't exist at detectable levels on modern audio systems.



I don't know who those would be, since we can almost always detect *some level* of something if we look for it with sensitive enough instruments; I thought the argument was always about audibility

And btw, if it turns out that one has to exhaust oneself, take coffee breaks, etc in order to hear a small amount of jitter 5/5 times in an ABX , I'm going to consider it a vanishingly small 'problem' for normal listening, and focus on things that matter instead.

That won't stop the scaremongers from doing what they do, of course.  Scaring people about jitter sells hardware 'upgrades'.
Title: Jitter Listening test files
Post by: ajinfla on 2014-12-09 22:31:16
I don't know who those would be

The same folks who claim all amps, wires, DACs, etc, etc. "sound the same".
You know, them.

cheers,

AJ
Title: Jitter Listening test files
Post by: amirm on 2014-12-09 22:49:47
I ran the tests again just now and documented a specific procedure for passing the tests legitimately: http://www.hydrogenaud.io/forums/index.php...st&p=884128 (http://www.hydrogenaud.io/forums/index.php?s=&showtopic=107540&view=findpost&p=884128)


Edit: Here is the new link to my results in the recycle bin: http://www.hydrogenaud.io/forums/index.php?showtopic=107718 (http://www.hydrogenaud.io/forums/index.php?showtopic=107718)
Title: Jitter Listening test files
Post by: Wombat on 2014-12-09 23:18:43
After complaining at amir i listened these samples the first time  Peace of cake to abx down to 0.125.

foo_abx 2.0 beta 4 report
foobar2000 v1.3.4
2014-12-10 00:10:25

File A: 30 Hz noticable jitter 0.0125.flac
SHA1: 7349f9f6449777a2c33693251099a6ed58821382
File B: no  jitter.flac
SHA1: 262cd6c4d4c73502a0142f867b00aae013fd13ce

Output:
DS : Primärer Soundtreiber

00:10:25 : Test started.
00:11:29 : 01/01
00:11:39 : 02/02
00:11:51 : 03/03
00:12:03 : 04/04
00:12:14 : 05/05
00:12:45 : 06/06
00:12:59 : 07/07
00:13:15 : 08/08
00:13:28 : 09/09
00:13:46 : 10/10
00:13:46 : Test finished.

----------
Total: 10/10
Probability that you were guessing: 0.1%

-- signature --
8c03ed033758c82830a239ea2a5f3f5ff12c910f
Title: Jitter Listening test files
Post by: MLXXX on 2014-12-10 00:07:50
Are you setting your trial number *before* you start your tests?

IOW, in the first results shown did you actually decide  beforehand, 'I will do 6 trials and stop'  and for second results shown , "I will do 5 and stop'?

If not, in the future  you should.

Certainly if you use progressive mode, where you can see your results as they happen, you should *not* stop at an arbitrary point....choose a number beforehand, and do the whole set.

I think this argument is much stronger if the test subject rapidly undertakes a series of incomplete and unsuccessful trials. If the incomplete trials are excluded from the reported results, the report is misleading, by excluding the unsuccessful results.

The beta version of the new plug-in in the version I downloaded it a few weeks ago sets a minimum number of trials at 8. That is actually quite a high number for an acoustic difference only audible by a particular listener who needs their hearing to be fresh. The question arises: what is the test subject to do if a point is reached when they feel they can no longer hear a difference.  Are they to answer recklessly without any belief in their answer? Or are they to abandon the exercise altogether at that point without any reportable result?

In a multiple choice exam for a university subject, there is an ethical question whether to answer questions by pure guesswork. The prevailing ethic (I believe) is to give an answer even to questions one has absolutely no idea about, the expectation being that others in the exam may do likewise, evening out the test results.  I am not sure how that translates to ABXing audio. For myself, if I feel I cannot hear a difference, I would prefer either to wait until I felt I could hear a difference (if there seems a reasonable prospect my hearing will recover), or abandon the test altogether. It is surely a form of deception to provide an answer to an ABX test by pure guesswork without any inkling as to whether it is what one actually hears.

In this particular exercise, knowing my hearing's tendency to lose sensitivity when listening to the same material, I will disclose that I actually had in mind doing 6 trials for the marginal jitter level file. However when doing the trials I became aware it was becoming increasingly difficult to have confidence in my ability to distinguish. Given that 5% is often adopted in statistics as an acceptable level of confidence, I finished after 5 trials, with a probability of guessing of 3.1%. I felt the statistical significance was sufficient, and I didn't want to wait another 15 minutes or so for my hearing to regain sensitivity.

I also have an aversion to any wrong answer, or guessing. To my mind, I either hear a difference or I don't. To have provided a 6th answer before my hearing recovered (based on a 50% likelihood it would turn out to be "right" anyway) was simply not a path I wished to go down.


And btw, if it turns out that one has to exhaust oneself, take coffee breaks, etc in order to hear a small amount of jitter 5/5 times in an ABX , I'm going to consider it a vanishingly small 'problem' for normal listening, and focus on things that matter instead.

I strongly disagree here, krabapple. If one hears a problem when one's hearing is fresh, and provided the problem actually sounds "bad" to one's ears rather than just "subtly different", then to my mind it is a significant issue. It matters not that one doesn't hear it on another occasion when one's hearing is fatigued.

For example, by the time I got to the 5th trial I was beginning to lose my ability to distinguish the samples based on the vibrato of the last sung note.

So I tried instead listening carefully to the guitar (something I hadn't previously focussed on to any great degree). The jitter affected sample did sound somewhat mushy in comparison and so I was confidently able to answer. I would rank the woolliness of the guitar as a significant impairment of the sound, to be avoided if technologically feasible. Guitar accompaniment is not something I usually take much notice of, but if it were a flamenco guitar solo performance I would like to be able to hear the guitar clearly, without any introduced mushiness.

However isn't the measured jitter level of actual equipment using HDMI quite a bit less anyway?  That is what I have taken away from this exercise. To the best of my knowledge I have never heard jitter effects outside of these test files Arny has provided.
Title: Jitter Listening test files
Post by: MLXXX on 2014-12-10 03:06:57
I note as a general comment that there is always the possibility of reducing jitter anyway in a playback device by use of a small buffer and a steady clock with a relatively slow time constant for fine adjustments to its clock rate, if there is any doubt about the short term timing stability of a stream of incoming digital audio. What extent of buffering is commonly in use I have no idea.

Buffering gets used in every device out there.  The problem with slow adjustment is the tracking range is very wide.  A receiver needs to lock onto sampling rates from 32 Khz to 192 Khz.  If it goes too slow, when you switch sources, you will have to wait many seconds for it to find and lock onto the incoming sample rate.  Customers will not accept input switching delays of more than 1 or 2 seconds whereas they are oblivious to jitter as a problem so fast switching wins.

If everyone is oblivious to the jitter then this would be an acceptable and appropriate outcome! However I assume you must be implying that some people can hear jitter in modern equipment.

I'm not privy to how phase-locked loops for audio streams are currently designed but I'd have thought it possible to have a coarse adjustment time constant to kick in if lock fails altogether such as when disconnecting and reconnecting an HDMI source, and a fine adjustment time constant to take over once approximate lock is achieved.

A mobile telephone connection would fall into a different category to playback of a Blu-ray disk. We have low expectations about audio quality for a mobile phone call and there may be packet loss depending on the instantaneous quality of the connection. An aggressive algorithm for phase lock may be appropriate in that application.

With Blu-ray, the source device should be clocking out the packets using a stable crystal controlled oscillator. The sink device could buffer using a slow time constant once lock was achieved. Similarly, a pc sound card should send HDMI packets with high precision to begin with. If the designer of an AVR wishes to tighten the timing even further by way of a buffer with a slow time constant, after approximate phase lock has been rapidly achieved with a fast time constant, that should be practical, I'd have thought.
Title: Jitter Listening test files
Post by: amirm on 2014-12-10 03:23:09
I'm not privy to how phase lock loops audio streams are currently designed but I'd have thought it possible to have a coarse adjustment time constant if lock fails altogether such as when disconnecting and reconnecting an HDMI source, and a fine adjustment time constant once lock is achieved.

What you are describing is dual PLL solution which indeed accomplishes this goal.  Alas, it is more expensive and complicated to design so you are going to see it in high-end gear, not mass market AVRs and such.

Here is a very revealing measurement I mad on a number of mass market AVRs and higher-end processors/DAC.  It shows how much incoming jitter the device filters.  0 db means no filtering at all.  Negative numbers show progressive amounts of filtering.  So the largest negative number is best.  The horizontal axis is the jitter frequency:

(http://amirviews.smugmug.com/photos/i-bs5DqCC/0/X2/i-bs5DqCC-X2.png)

As you see the mass market AVRs all bunch up on top.  Some even amplify jitter!  That is a symptom of the peaking in the PLL loop filter.

Next best is my 10 year old Lexicon 12B processor.  Much improved is the product from its sister company, the Mark Levinson 502 processor.  These are both obsolete products yet outperform their much newer mass market AVRs from Onkyo, Pioneer, Yamaha and Anthem.

Producing absolutely superb performance is my ancient, circa 2000 Mark Levinson No 36S DAC. 

What this means is that jitter in mass market devices is influenced by upstream devices/interconnect.  So the performance I get with the same AVR may differ than you using the same AVR!

Clearly these techniques are not new.  They just cost money and talent, something that is hard to come by in the money losing mass market AV business.
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-10 15:31:12
I'm not privy to how phase lock loops audio streams are currently designed but I'd have thought it possible to have a coarse adjustment time constant if lock fails altogether such as when disconnecting and reconnecting an HDMI source, and a fine adjustment time constant once lock is achieved.

What you are describing is dual PLL solution which indeed accomplishes this goal.  Alas, it is more expensive and complicated to design so you are going to see it in high-end gear, not mass market AVRs and such.

Here is a very revealing measurement I mad on a number of mass market AVRs and higher-end processors/DAC.  It shows how much incoming jitter the device filters.  0 db means no filtering at all.  Negative numbers show progressive amounts of filtering.  So the largest negative number is best.  The horizontal axis is the jitter frequency:

(http://amirviews.smugmug.com/photos/i-bs5DqCC/0/X2/i-bs5DqCC-X2.png)

As you see the mass market AVRs all bunch up on top.  Some even amplify jitter!  That is a symptom of the peaking in the PLL loop filter.

Next best is my 10 year old Lexicon 12B processor.  Much improved is the product from its sister company, the Mark Levinson 502 processor.  These are both obsolete products yet outperform their much newer mass market AVRs from Onkyo, Pioneer, Yamaha and Anthem.

Producing absolutely superb performance is my ancient, circa 2000 Mark Levinson No 36S DAC. 

What this means is that jitter in mass market devices is influenced by upstream devices/interconnect.  So the performance I get with the same AVR may differ than you using the same AVR!

Clearly these techniques are not new.  They just cost money and talent, something that is hard to come by in the money losing mass market AV business.



It is all just numbers, and in this case I'm not even seeing any absolute numbers, just relative numbers to some product I really know nothing about.

When it comes to detecting jitter by ear, Amir's ABX test results to date correspond to approximate -55 dB 30 Hz jitter, which is 30-40 dB worse than the worst commercial product that I know of.  There are two steps of tougher tests in this Dropbox Folder:

https://www.dropbox.com/sh/b35feharwc7doty/...BTPbBa1JZa?dl=0 (https://www.dropbox.com/sh/b35feharwc7doty/AADTO9LPjXt9KwuBTPbBa1JZa?dl=0)

Title: Jitter Listening test files
Post by: Wombat on 2014-12-10 16:27:36
Here is my 0.00625 result and i have to admit it is a pretty big step from 0.0125 but overall it sounds a bit muddy on the guitar strings. I guess the lowest jitter one i have to pass.
HD-590. old X-Fi

foo_abx 2.0 beta 4 report
foobar2000 v1.3.4
2014-12-10 17:18:28

File A: 30 Hz jitter marginal level .00625.flac
SHA1: ee1083c40daa4ad36c07081162f2b3326bfe447c
File B: no  jitter.flac
SHA1: 262cd6c4d4c73502a0142f867b00aae013fd13ce

Output:
DS : Primärer Soundtreiber

17:18:28 : Test started.
17:19:49 : 01/01
17:20:18 : 02/02
17:20:43 : 03/03
17:20:56 : 04/04
17:21:11 : 05/05
17:21:29 : 06/06
17:21:53 : 07/07
17:22:11 : 07/08
17:22:32 : 08/09
17:22:47 : 09/10
17:22:47 : Test finished.

----------
Total: 9/10
Probability that you were guessing: 1.1%

-- signature --
8594ec05b059f9ae0e4edf3a3173bdbd8665a65e
Title: Jitter Listening test files
Post by: greynol on 2014-12-10 16:44:18
I tried ABX training with that yesterday and was able to get sets of 5 in a row but only with in-between breaks.  I found increasing the volume level made it more difficult.  I was using IEMs as well, so microphonics and occlusion were not helping.
Title: Jitter Listening test files
Post by: Wombat on 2014-12-10 16:54:15
Yesterday night i didn't really try lower as 0.0125. This log above was my first try today after some relaxed sofatime. I was surprised myself because the beta foobar plugin shows the result only at the end.
Title: Jitter Listening test files
Post by: greynol on 2014-12-10 16:57:18
Even under the best circumstances, I'm pretty confident I wouldn't be able to go much lower than 0.00625.
Title: Jitter Listening test files
Post by: Porcus on 2014-12-10 17:13:01
A receiver needs to lock onto sampling rates from 32 Khz to 192 Khz.  If it goes too slow, when you switch sources, you will have to wait many seconds for it to find and lock onto the incoming sample rate.  Customers will not accept input switching delays of more than 1 or 2 seconds whereas they are oblivious to jitter as a problem so fast switching wins.


That explains why "jitter" was never mentioned by hi-fi sellers back in the day when consumers only had one digital source (CD). Never ever! 
Title: Jitter Listening test files
Post by: greynol on 2014-12-10 19:52:33
For fun:
Code: [Select]
foo_abx 2.0 beta 8 report
foobar2000 v1.3.1
2014-12-10 11:41:45

File A: 0 - no jitter.flac
SHA1: ffdad7236acf795cb14a3816abf8c3a0da6b5bf4
File B: 1 - 30 Hz threshold jitter 0.00312.flac
SHA1: 7445aff311ed89263769042c856c089e0f97534d

Output:
DS : Primary Sound Driver, 16-bit
Crossfading: NO

11:41:45 : Test started.
11:45:51 : 01/01
11:46:05 : 01/02
11:46:33 : 02/03
11:46:51 : 02/04
11:47:01 : 03/05
11:47:44 : 04/06
11:47:56 : 04/07
11:48:03 : 05/08
11:48:16 : 06/09
11:48:35 : 07/10
11:48:52 : 08/11
11:49:13 : 08/12
11:49:26 : 08/13
11:49:36 : 09/14
11:49:41 : 10/15
11:49:49 : 11/16
11:49:49 : Test finished.

 ----------
Total: 11/16
Probability that you were guessing: 10.5%

 -- signature --
5d06b1bdcf6f49cdca391cd1607dd7acb9fddc53
Title: Jitter Listening test files
Post by: Wombat on 2014-12-10 20:32:37
Nice one greynol!

Is this really what jitter does to audio? Audiophiles report all kinds of weird degrations due to it.
Most of the time it is blamed to sound like unpleasant digitalis scratchy distortion.
With these samples the problem sounds absolutely the way i would blame something to be wrong with analog gear.
Title: Jitter Listening test files
Post by: greynol on 2014-12-10 20:45:45
Thanks.  If I repeat the test and do slightly better, I'm pretty sure the two combined will have significance.

In response to your earlier posts I mistakenly confused the 0.00625 for the 0.003125 file.

...so let me amend what I said earlier:
Even under the best circumstances, I'm pretty confident I wouldn't be able to go much any lower than 0.00625 0.003125.
*

In terms of sound quality, I'm really just focusing on clarity in only very short segments of the guitar.

Most audiophiles are full of shit.  That's why I call them placebophiles.  They'll attribute all sorts techno-babble to the stuff they imagine hearing.

(*) I'm not all that convinced that the fidelity of this Joni Mitchel clip is really all that stupendous, however!
Title: Jitter Listening test files
Post by: mjb2006 on 2014-12-10 21:43:08
I thought I understood what jitter was, but I really need someone to dumb this down for me. What do the 30 Hz and the 0.003125 to 0.1 figures represent?

Were the files produced by varying the timing of the samples, i.e. each sample was taken not precisely 1/44100th of a second apart? Or is it a simulation of the effects of that? Or something else?

Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-11 14:02:49
I thought I understood what jitter was, but I really need someone to dumb this down for me. What do the 30 Hz and the 0.003125 to 0.1 figures represent?


Jitter is FM distortion, which interestingly enough is usually far more of a problem in the analog domain than the digital domain. In the analog domain it is called flutter and wow and most of the ways to address it are mechanical. For example high quality analog tape recorders have scrape flutter filters which are massy mechanical rollers that are placed in contact with the tape and tend to stabilize its speed over the heads.

In the analog domain the leading causes of FM distortion are analog media such as the LP and tape both of which are pretty horrendous if you look at the comparable numbers. The adoption of digital media vastly reduced this problem.

Speakers can also be strong sources of analog FM distortion. Multi-way speakers can strongly reduce this problem. The adoption of subwoofers has probably reduced the incidence of FM distortion due to speakers to a great degree. Attempting to get strong deep bass out of small speaker drivers with just one or two frequency bands favors the creation of more FM distortion.

FM  multipath can also introduce jitter. Jitter from this source can be very audible but is usually more sporadic in its effects and is generally far worse for mobile receivers.

Multipath can also cause jitter in digital TV which will effect both the audio and the video. Modern OTA digital TV receivers now contain special circuits to minimize it. It is probable that the classic Benjamin and Gannon AES paper about jitter was at least partially stimulated by concerns about audible jitter due to digital TV reception.

Quote
Were the files produced by varying the timing of the samples, i.e. each sample was taken not precisely 1/44100th of a second apart? Or is it a simulation of the effects of that? Or something else?


The samples I provide are produced in the digital domain by varying the timing of the data contained in the samples by means of complex DSP algorithms that I am not privy to. I know they work based on exhaustive technical tests. For example 30 Hz jitter introduces a cyclic change in the frequency of the recorded signal over the span of  more than 100 samples. The clock rate or inter-sample timing was never actually changed.
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-11 14:19:31
Is this really what jitter does to audio?


Jitter is the same as tremelo and thus has two orthogonal dimensions - frequency of modulation  and magnitude or depth of modulation.  This is 30 Hz jitter. Real world audio system jitter can vary in frequency from less than 1/3 Hz (LP rotation) to over 500 Hz, so this is just one kind of jitter of a great many.

I have prepared a few samples with very large amounts of jitter at 200 Hz and 500 Hz. You  can download them from here:

Dropbox link to 200-500 Hz jitter files (https://www.dropbox.com/s/u01ntkpl8hyfioc/200-500%20jittered%20joni%2010-11-2014.zip?dl=0)

I need to know whether other people can hear the jitter in these files well enough for them to be used as training files.

Quote
Audiophiles report all kinds of weird degrations due to it.


I can only echo Greynol's comments about audiophile=placebophile. My experience and the scientific literature suggest that most audiophiles are describing events that exist only in their imaginations when they talk about digital dither in good audio gear.

Quote
Most of the time it is blamed to sound like unpleasant digitalis scratchy distortion.


IME most so-called digitalis is actually due to poorly produced recordings and poor speakers and room acoustics. IOW it has nothing to do with the intherent properties of digital audio as is currently implemented.

Quote
With these samples the problem sounds absolutely the way i would blame something to be wrong with analog gear.


As I point out in another post I just made to this thread, problems in the analog domain are the sources of most audible jitter.

I find it ironic that jitter was not treated very seriously by audiophiles until it was mostly reduced by vast amounts with the introduction of the CD.
Title: Jitter Listening test files
Post by: lithopsian on 2014-12-11 14:37:57
I find this frequency of jitter most noticeable in the tone at the end, where it is fairly easy to spot.  I didn't find that with the 30Hz jitter.
Title: Jitter Listening test files
Post by: julf on 2014-12-11 14:40:16
Jitter is the same as tremelo and thus has two orthogonal dimensions - frequency of modulation  and magnitude or depth of modulation.


I always thought tremolo was chopping/amplitude modulation, and vibrato was FM.

Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-11 15:24:39
Jitter is the same as tremelo and thus has two orthogonal dimensions - frequency of modulation  and magnitude or depth of modulation.


I always thought tremolo was chopping/amplitude modulation, and vibrato was FM.



That is correct. Jitter is Vibrato or FM. Typo!  Tremolo is AM.
Title: Jitter Listening test files
Post by: Hotsoup on 2014-12-11 18:05:59
Now I'm confused about an electric guitar's "whammy" bar because it's sometimes called tremolo. 
Title: Jitter Listening test files
Post by: greynol on 2014-12-11 18:09:53
The whammy bar alters the pitch, so the name tremolo is misapplied.
Title: Jitter Listening test files
Post by: mjb2006 on 2014-12-11 18:40:16
When digital jitter-phobes say they need a pro/audiophile-grade DAC and interconnects because the jitter in consumer-grade gear makes everything sound worse than analog, is this FM/vibrato effect the thing they're worried about? (regardless of whether they actually hear it) ... Or does that kind of jitter, when taken to extremes like in these audio files, have a different sound?
Title: Jitter Listening test files
Post by: greynol on 2014-12-11 18:45:33
You'll have to ask them, but make sure you bring your waders.
Title: Jitter Listening test files
Post by: Case on 2014-12-11 19:28:33
I have prepared a few samples with very large amounts of jitter at 200 Hz and 500 Hz. You  can download them from here:

Dropbox link to 200-500 Hz jitter files (https://www.dropbox.com/s/u01ntkpl8hyfioc/200-500%20jittered%20joni%2010-11-2014.zip?dl=0)

I need to know whether other people can hear the jitter in these files well enough for them to be used as training files.


I had trouble hearing the problem in the music in the 200 Hz version at first. The jitter was very audible in the ending tone though. After a little while the dirty sound was audible during the guitars too.
The 500 Hz version was audible in its entirety without effort.
Title: Jitter Listening test files
Post by: Wombat on 2014-12-11 19:53:34
I have prepared a few samples with very large amounts of jitter at 200 Hz and 500 Hz. You  can download them from here:

Dropbox link to 200-500 Hz jitter files (https://www.dropbox.com/s/u01ntkpl8hyfioc/200-500%20jittered%20joni%2010-11-2014.zip?dl=0)

I need to know whether other people can hear the jitter in these files well enough for them to be used as training files.

Thanks Arny. Especialy the exaggerated 500Hz sample has indeed an ugly metallic signature to me just what i expect from jitter. The 200Hz sample is not annoying but also clearly audible.
Title: Jitter Listening test files
Post by: MLXXX on 2014-12-12 00:26:40
30 Hz max jitter 0.1.flac
30 Hz Severe Jitter 0.05.flac
30 Hz jitter strong level .025.flac
30 Hz noticable jitter 0.0125.flac
30 Hz jitter marginal level .00625.flac
30 Hz threshold jitter 0.00312.flac

No one to date has submitted a successful ABX report for the "threshold" file, but some have succeeded with the "marginal" file. I thought it worthwhile to report that the subjective disturbance (at least for my ears) does not follow a linear type of relationship along the lines of a doubling or halving of the effect when moving from one jitter level in the above files to the next. Rather there is a much bigger change. For example, in going from listening to the "noticeable" file to the "strong" file, the subjective impact is many times more pronounced for the "strong" file.

I have prepared a few samples with very large amounts of jitter at 200 Hz and 500 Hz. You  can download them from here:

Dropbox link to 200-500 Hz jitter files (https://www.dropbox.com/s/u01ntkpl8hyfioc/200-500%20jittered%20joni%2010-11-2014.zip?dl=0)

I need to know whether other people can hear the jitter in these files well enough for them to be used as training files.

I think the effect on the guitar would be obvious enough for people with good hearing, but not over-obvious, for use as training files.

I note that introducing a stable jitter at one frequency need not sound unpleasant when applied to some instruments (though this can be a question of personal preference). For my ears, the guitar sounds a bit like a harpsichord in these files. A more complex, and arguably more interesting, sound. The jitter doesn't seem to improve the vocal in any way however!

I'm not all that convinced that the fidelity of this Joni Mitchel clip is really all that stupendous, however!

I agree. 

I think the simplicity of plucked/strummed guitar strings, as we have in this Joni Mitchel clip, is good for exposing frequency variations. Another possibility would have been piano. I recall with domestic open-reel tape recorders, and cassette tape recorders, that flutter could often be heard readily with the sound of the piano.
Title: Jitter Listening test files
Post by: greynol on 2014-12-12 06:16:44
So I get bragging rights if I pass*?

If I have time, I'll do it.

(*) the downside is that the information will likely be misused either out of ignorance or to serve some agenda.
Title: Jitter Listening test files
Post by: Woodinville on 2014-12-14 02:37:40
How about make a signal that consists of equal parts of 18kHz and 19kHz signal and use that for jitter detection?
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-14 12:40:57
How about make a signal that consists of equal parts of 18kHz and 19kHz signal and use that for jitter detection?


Tried it.

18 KHz and 19 KHz are inaudible to most people including me.

Adding frequency modulation creates sidebands that are tightly clustered around 18 KHz and 19 KHz, and they are also inaudible to most people.

It would be nice to have a test signal that:

(1) Is audible to most people

(2) Is similar to a musical sound
Title: Jitter Listening test files
Post by: greynol on 2014-12-14 14:32:22
It would be nice to have test signals where the jitter:

(1) Mimics the modulation found in typical situations, including the current placebophile paranoia: HDMI jitter.

(2) Is at extremely exaggerated levels in order to be audible to most people.

The original content should contain music that that was optimally recorded and produced. If a synthesized signsl makes the jitter easier to detect, it should be included as well. It may need to be more complex than a single tone.
Title: Jitter Listening test files
Post by: Arnold B. Krueger on 2014-12-15 10:06:06
It would be nice to have test signals where the jitter:

(1) Mimics the modulation found in typical situations, including the current placebophile paranoia: HDMI jitter.


Jitter has 3 strong independent influences which are:

(1) Primary Jitter frequency which is the same as displacement in the frequency domain of the primary set of sidebands from the carrier when we modulate a single pure tone.

(2) Primary Jitter amplitude which is the height of the first pair of sidebands as compared to the carrier.

(3) Jitter shape factor which is the rate at which the sidebands fall off with increasing order once we progress past the first few harmonics.

Doable with the caveat that the primary technical properties of HDMI jitter is far from being the same in various pieces of comparable equipment, and doesn't even stay the same for the same piece of equipment depending on the operational mode of the system. There is the potential for different primary jitter frequencies and primary jitter amplitudes for every permutation of 3 different influences:

(1) The source component (BD player, Cable Box, or AV Player).
(2) The specific recording because a lot of HDMI jitter relates to the frame rate which itself can vary among recordings.
(3) The specific A/C component that takes in a digital signal from a source component and puts out analog signals (Surround Processor, AVR, DAC, etc.).

I think that the second influence which is primary jitter frequency, that need to be tested are:

(1) 30 Hz  (representing 24 and 30 Hz)

(2) 60 Hz (representing 50 and 60 Hz)

(3) 120 Hz (representing 100 and 120 Hz)

(4) 240 Hz  (representing 200 and 240 Hz)

(5) 500 Hz (representing 420, 500, and 600 Hz)

There is a third independent influence that relates to jitter which I can't find in the literature but I know it it exists - I'll call it Shape Factor. The Shape Factor relates to how the various harmonics of the primary fall off as their order increases.  For example when you FM modulate a carrier strongly you don't create just one pair of sidebands, you create a sequence of sideband pairs whose amplitude falls off with their order (this are why we use Bessel Functions to predict their amplitudes). However the rate at which they fall off can vary from not dropping off at all with increasing order, to dropping off very rapidly with increasing order.  At this time, I suggest we come up with an average global shape factor and worry more about the stronger independent influence which is primary jitter frequency.\

(http://www.avsforum.com/photopost/data/2374109/6/62/621aa066_pioneeravrj-test.png)

In the test above, the primary jitter frequency is 30 Hz, the primary jitter amplitude is approximately -77 dB, and the primary shape factor is about -6 dB per octave after the first few harmonics of the primary jitter frequency.

Rather than try to mix and match all of these influences by testing different real components, it seems to be be more reasonable to ascertain a range of jitter frequencies that would be tested.

I figure that it would take from 5 to 8 different sets of ABX tests to gather a fairly complete set of data about this issue. The independent parameter of each set would be the jitter frequency.

Each set of ABX tests would involve 5-8 different tests. The independent parameter of each test would be jitter level.
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(2) Is at extremely exaggerated levels in order to be audible to most people.


Doable given that there were listeners who would actually perform the 25 to 64 different ABX tests that would be required, at least 16 trials each.

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The original content should contain music that that was optimally recorded and produced. If a synthesized signals makes the jitter easier to detect, it should be included as well. It may need to be more complex than a single tone.


I think that using synthesized signals has its place and may be a valuable tool for listener training, but in the end it is all about how typical music, dialog, and EFX (simulations or samples of natural sounds) sound.
Title: Re: Jitter Listening test files
Post by: C87P66 on 2019-02-09 01:10:56
So how much jitter was in the files? I tried the files on https://web.archive.org/web/20130907071133/http://www.cranesong.com/jitter_2results.html and was able to make out the difference of 300hz 300ps in ABX. Is that site trustworthy? Can you correlate your tests to ps estimates? Thank you!
Title: Re: Jitter Listening test files
Post by: greynol on 2019-02-09 16:53:21
https://hydrogenaud.io/index.php/topic,115942.0.html
Title: Re: Jitter Listening test files
Post by: C87P66 on 2019-02-10 02:55:05
https://hydrogenaud.io/index.php/topic,115942.0.html


Thank you for the information as I was completely unaware. I read many of his posts including the one on channel delay audibility which completely changed my beliefs on the matter. His contributions will surely continue to be useful and enlightening to many through the internet for a long time to come.
Title: Re: Jitter Listening test files
Post by: jsdyson on 2019-02-12 04:25:03
The 'jitter' is caused by a sloppy clock in the HDMI to audio conversion.  There is nothing in the early portions of the process (including CDROM timing) unless it is resolved back down to audio and back to digital that can cause signifncant jitter.  So, using HDMI with sloppy conversion hardware (which is essentially an D/A converter) will certainly cause jitter.  Jitter IS bad, but I didn't realize that some HDMI converters were THAT bad.  (There are mechanisms for micro amounts of jitter to propagate through hardware, but it is by far ground and radiation that causes the non D/A & LAST clock jitter.)  The propagated jitter through digital hardware is diminished greatly for every clocked buffer used, and is probably totally nil at the first step.  Sloppy HW can let stuff through, in a data circuit way, but that will not really happen.  IT IS 99.999% ground and radiated issues, and good RF design will 'totally' eliminate that.
The HDMI stuff has always worried me, because there is little reason for the normal HDMI converter in the last HW to be of any reasonable quality at all.

John
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