Talk:Jitter

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This is the talk page for discussing improvements to the Jitter article.
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This article contains material from the Federal Standard 1037C (in support of MIL-STD-188), which, as a work of the United States Government, is in the public domain.

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[edit] Jitterlyzer

The following conversation originated at User talk:Daichinger and User talk:DragonHawk, and was moved here. See also article history.

Hi, why are you deleting the additions I am making to the Jitter page? --Daichinger 13:36, 11 July 2007 (UTC)

Because it appears to be an advertisement. Please see the links in the warnings above for why. I've reverted three times now. Further reverts would be frowned upon, so next I will contact the admins and let others decide, but I will warn you that you may get blocked from editing Wikipedia if you don't at least attempt to justify your actions. —DragonHawk (talk|hist) 13:46, 11 July 2007 (UTC)
I think the Jitterlyzer should be added to this page because it is the only device that can measure Jitter in sRIO and PCIe. These are buses that are significantly used in industry and thus the Jitterlyzer should be included. --Daichinger 14:06, 11 July 2007 (UTC)
Again, please read the pages I have linked to. Wikipedia is not a vehicle for advocacy. It is not a place for personal opinions. If you can cite a reliable source as to why this product is somehow notable, then do so. If you're just pushing a product, you're in the wrong place. —DragonHawk (talk|hist) 14:16, 11 July 2007 (UTC)
How is this?
The Jitterlyzer performs physical layer serial bus jitter analysis. It is able to inject a controlled amount of jitter and measure the characteristics of incoming jitter. This is usefull when a user needs to see if the eye is going out of scope, which will cause a high bit error ratio.
--Daichinger 21:01, 11 July 2007 (UTC)
I don't consider a press release announcing a product a reliable source. Other Wikipedians may disagree with my opinion on that. If you believe you have no conflict of interest here, and you are not just trying to promote or advocate this product, we can ask for a third opinion.
Let me ask you this: Why are you so keen on getting mention of this product added to the article? What is your motivating interest here? If you explain where you are coming from, it might help myself and others understand why this product deserves mention in an encyclopedia.
By the way, in case it isn't obvious, when I link to something (like this), that is an invitation for you to click the link and read up on guidelines that help explain my position. If you understand and speak to said guidelines, we will both have a much easier time. Thanks!
—DragonHawk (talk|hist) 00:33, 12 July 2007 (UTC)
This article is about jitter, it lists ways to measure it, reduce it, and prevent it. The measuring aspect currently only covers measure DVDs and CD-Roms and it is just a single line a stub if you will. Those measuring devices are called Jitter-meters. Later in the acticle it 'specifically' talks about clock jitter. A jitterlyzer measures clock jitter. I was wrong in mentioning a specific product. It is a brand new type of test equipment and doesnt currently fall under category of jitter-meter which acording to this article only covers DVDs and CDs. So since this article talks about jitter in CDs and mentions ways to measure it, should'nt it also cover ways to measure clock jitter?
Further more I believe I am inside the gidelines that are set forth in the links above. I am trying to make this wikipedia article more comprehensive.
--Daichinger 13:46, 12 July 2007 (UTC)

[edit] Moved from end of article

"The word 'jitter' can be used to refer to those people who dress mainly in black, keep their hair long and listen to punk rock."

Yep. 80.203.115.12 17:16, 27 October 2005 (UTC)

[edit] Rewriting of Jitter Types

I changed a fair amount of the guts of the article. In some cases, as in the definitions of "period" vs "cycle-to-cycle" jitter, I changed it back to what it was in Nov. 2004. If someone thinks that definition is wrong, please comment here so we can discuss before changing it. I'm pretty sure the article is more right than it used to be.

other changes.

  1. rejected the false paradigm shift. Jitter has always and will always be a concern for all links. Added some additional interconnects
  2. the qualitative or quantitative thing seemed a bit strange the way it was. It's like saying you can measure something as speed or as km/h.
  3. jitter does not have to be rapid or repeated.. and in fact, the article later says so. Hence, that had to go.
  4. the standard deviation of peak-to-peak was confusing.
  5. phase departure and phase perturbation.. are these industry-standard terms? I've never heard them as such.
  6. usually random but if cyclc it may be expressed in hertz. Well.. anything cyclic can be expressed in hertz (actually.. no.. it's cycling can be expressed in hertz.. the thing itself can strictly not be). Also, there's no reason to say that phase jitter is usually random, as far as I know.
  7. peak to peak period jitter is the worse case of cycle to cycle jitter. This is not true. Read that JEDEC jitter definition. It defines period vs cycle-to-cycle jitter.

I also changed the name of this section from jitter types to phase jitter metrics because I think the term jitter types is more suited to describing actually different types of jitter (eg. deterministic jitter, sinusoidal jitter, random jitter) as opposed to just how it is measured.

Jurgen Hissen 07:16, 22 August 2006 (UTC)

[edit] Questions About Jitter

Most of these are questions about jitter that occurred to me while reading the article.
Maybe I will even try answering some of them.  :-)

  • What distinguishes jitter from noise in general?
  • Is jitter always random, or can it be deterministic too?
  • Why does jitter cause problems?
  • Can jitter cause problems in analog systems in addition to digital systems?
  • Where does jitter occur in CD/DVD drives?
  • What causes jitter?
  • What is an eye diagram and how is it used?

--Jtir 21:27, 9 September 2006 (UTC)

The pdf available at the Audio Precision website has information on digital audio jitter, 'Measurement Techniques for Digital Audio' by Julian Dunn. http://ap.com/library/technotes.htm Enescot 21:18, 16 March 2007 (UTC)

[edit] Jitter ...

[edit] "jitter"/"chitter"/"chatter"

Jitter is a word in general usage for the tendency of something to jump abruptly backwards and forwards. It supposedly comes from the Scots word, "chitter", meaning to shiver, which might in turn be related to the onomatopoeic word "chatter", as in, "Her teeth chattered due to the cold".

See also "jitterbug", a dance with fast jerky movements, and "jittery", to be prone to sudden movements when startled, due to anxiety

"chatter" can refer to a constant stream of Morse Code signalling (signal chatter), or a continuous stream of fast staccato speech (-> chatterbox) … that then gets shortened to chat (as in, "We had a nice chat"). This has been adopted by the internet community (eg chatrooms)

[edit] "jitter interpolation"

Anyhow, back to jitter and telecoms …

As well as referring to unwanted clock timing errors, jitter is also a deliberate technique used for obtaining sub-bit resolutions in digital audio and image processing, using spare bandwidth to trade off unneeded "timing" resolution into additional "value" resolution.

[edit] "jittered" interpolation on output signals (obsolete term?)

If we have an audio DAC running at twice the rate of your sample frequency, we can reproduce output values with "half-bit" resolution by deliberately "jittering" the lowest bit between 0 and 1, and then low-pass filtering out the jitter signal to leave an smoothed "averaged" intermediate value. If the DAC runs at eight times your sample frequency, we can adjust the proportion of "ones"s to "zero"s, to achieve one eighth of a bit accuracy, and so on. This output can be in simple PWM form (see: "one-bit convertors"), or, to filter out these high-frequency artefacts more efficiently, the output stream of ones and zeroes may be deliberately organised to reduce the occurrence of consecutive ones or zeros, to shift the frequency of this jitter noise as far above the base frequency as possible.

[edit] Jittered interpolation on sampling

For sampling at sub-bit resolutions, you can mix the signal with low-level high-frequency noise (out of the audio range), oversample, and then the statistical proportion of ones and zeroes in your lowest bit as it gets toggled at ultrasonic rates by the noise, tells you roughly where the underlying signal level was within that lowest bit range. A majority of ones tells you that it was a high sub-bit value, a majority of zeroes tells you that it was a low sub-bit value. So you just average a succession of jittered sample values together to give you the final higher-resolution sample value. The noise source is required to "tickle" the ADC into jittering, so that it doesn’t just slowly step between discrete values as the input signal value rises and falls.

This technique was probably only worthwhile when component counts were a significant factor. The drastic drop in prices with chip-scale integration probably makes this technique redundant, a DAC/ADC feedback loop with an oversampled output signal and a "successive approximation" approach is probably simpler and more reliable to implement, since the hardware has now gotten so cheap.

[edit] jitter and information theory/QM

As a general statistical method for shunting information between domains (e.g. the frequency domain and the accuracy domain), jitter principles show up in information theory and quantum mechanics. The technique is useful in a variety of situations where we want to take measurements below the level of an apparently unavoidable quantisation threshold.

[edit] jitter interpolation and image sampling

An analogous effect can be used in digital image processing to obtain images with sub-pixel resolution. Instead of taking a single image with a standard exposure (which would be limited to the resolution of the sensor , and might also suffer from blurring if the camera is unsteady), jitter techniques can make positive use of camera shake to take a succession of less blurred shorter-exposure images, which can then be enlarged, and then aligned and rotated with sub-pixel accuracy to obtain the best fit, with the adjusted images then being superimposed to produce the final composite image. While the noise levels in each individual picture will be higher, this background noise will tend to cancel in the final image. The degree of extra image resolution that can be achieved this way will depend on the number of images taken, and the accuracy of the sub-pixel realignment process. One might expect the best results if the angle of the image varies slightly between images as well as the offset of the image. Rotating and offsetting multiple images requires a certain amount of processing power, but this is not an insuperable limitation when cleaning up and enhancing image data from, e.g., the Hubble space telescope.

A more "consumerised" application of jitter interpolation might be to fit the CCD image sensor of a consumer digital camera with a piezo transducer to sweep the CCD sensor sideways across the image field while a photograph is being taken in order to produce an orderly series of offset images that can be processed and assembled by the camera's embedded software to achieve a "virtual resolution" for the camera that is higher than the resolution of is sensor array. I don’t honestly know if jitter interpolation is already being used in mass-market electronic cameras yet, but if it's not, it's probably just a matter of time before it shows up. ErkDemon 05:38, 23 March 2007 (UTC)

[edit] Fair use rationale for Image:Unstressed Eye.PNG

Image:Unstressed Eye.PNG is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to insure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.

If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images uploaded after 4 May, 2006, and lacking such an explanation will be deleted one week after they have been uploaded, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.

BetacommandBot 22:34, 25 October 2007 (UTC)

[edit] Should this be merged with Delay Jitter?

http://en.wikipedia.org/wiki/Delay_jitter —Preceding unsigned comment added by 202.124.85.135 (talk) 00:23, 30 October 2007 (UTC)

Even better, merge Delay jitter with Packet Delay Variation, of which it is a synonym. I have just done the deed. --Heron (talk) 13:32, 10 May 2008 (UTC)