LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


[email protected]


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Monospaced Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  February 2013

ARSCLIST February 2013

Subject:

Re: Jitter (was Re: [ARSCLIST] Audibility of 44/16 ?)

From:

Jamie Howarth <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Mon, 11 Feb 2013 16:52:51 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (95 lines)

Oh man this is so simple.
The clock has to be stable and the pulse train evenly spaced, whether its magnetic domain playback, or digital word/pulsed/filtered.
Analog, digital, whatever.

 Low frequency rate analog jitter I.e flutter causes blurring and distortion in a fairly direct manner, shifting the signal in the frequency domain. Average amplitude HF response is slightky higher, obviously more coherence. As transients smear, everything's duller.

Digital jitter creates crazy situations where adjacent positive-going samples can actual develop negative hitches and overshoots because the number going in is right, but early or late..so the output waveform is mis-shapen.

This is simply a loss of synchronicity with the original waveform. Picture a series of 44.1k samples for ten perfect seconds Then one of them arrives next week, Followed by 10 more an hour later, then back to 44.1k... That will be a very mis-shapen output wave, with a stepped response that the filter won't smooth. Extreme case but identical.
Early ladder DACs had also had long settling times and capacitive voltage retention that could create further errors, they were, after all, sample and holds. So that created a mambo effect.

All of this manifests as graininess and image collapse. So, by the way does fast flutter and scrape flutter.
If the error correction kicks in on a CD it will likely get the data back. If it's copied to hard drive as data it will either reject the disc as unreadable or the data will be stored perfectly.

Asymmetrical data delivery as contrasted with waveform reconstruction is immaterial or every piece of downloaded software would crash. Bits is bits whether it takes a microsecond to transmit and store or a week.
But to reconstruct the wave the buffered data has to come out perfectly stepped in time. Which these days is easy. An Iphone 4s playing a .wav sounds amazing - wolfenson DAC, low jitter.
That's all it takes. Better analog circuits? Sure. But timing is more important.

What we do is similar, but with tape. Using a 150hHz click from the original recorder we recover something much closer to the original wave shape before the mechanical jitter, again different spectra but basically identical, the transport distorts the wave shape on recording and further on playback. Similar perceptual effects when the time-base is restored.


Please pardon the misspellings and occassional insane word substitution I'm on an iPhone

On Feb 11, 2013, at 12:33 PM, Tom Fine <[log in to unmask]> wrote:

> Hi John:
>
> I think Don was saying the same thing I have been told by more than one learned EE specializing in digital recording and playback, plus what Mike Gray was saying (as I interpreted it) -- you can fix jitter that is introduced in the A-D stage. You CAN strip out jitter from the D-A stage by re-clocking the data stream (which is what Benchmark and others do). Preferred USB interfaces are asynchronous, which (I think) means they do not rely on the unreliable computer clock but rather strip out clock information from the incoming data stream and re-clock it. I think this involves cache-ing a certain amount of data, then applying the new internal clock, sending that to the DAC, which is locked to the internal clock, and thus removing jitter from the incoming data stream.
>
> Konrad, please specify what of Mike Gray's posting you are calling myth. Are you saying that jitter can't be introduced in the A-D stage?
>
> By the way, this is a really interesting discussion. I'm waiting for Goran and perhaps others to weigh in with some error-correction!
>
> -- Tom Fine
>
> ----- Original Message ----- From: "John Haley" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, February 11, 2013 12:13 PM
> Subject: Re: [ARSCLIST] Jitter (was Re: [ARSCLIST] Audibility of 44/16 ?)
>
>
>> Don,
>>
>> One can see lots of devices that claim to "correct" jitter problems and you
>> see them use verbs like "reclocking" to correct jitter errors. Are you
>> saying this is a myth, and that all that can be done is for a device to
>> prevent jitter at the outset, not fix it? But if devices can fix an
>> incoming stream of data to correct jitter errors, it would seem that a
>> recording containing a data stream with jitter errors could just as easily
>> be corrected. A data stream is a data stream. I don't have any answers,
>> just questions ...
>>
>> Thanks,
>> John Haley
>>
>>
>>
>> On Mon, Feb 11, 2013 at 10:11 AM, Don Cox <[log in to unmask]> wrote:
>>
>>> On 11/02/2013, Tom Fine wrote:
>>>
>>> > Can jitter be introduced on the A-D stage? As I understood Mike Gray's
>>> > posting, he was saying jitter can be induced from the get-go, in the
>>> > A-D process. Konrad, do you know that to be untrue?
>>> >
>>> A->D involves sampling the analog voltage at regular intervals. If the
>>> intervals are not exactly regular (i e jitter), the digital record cannot
>>> be
>>> accurate.
>>>
>>> I can't think of any way of correcting such recordings.
>>>
>>> > Also, I've been told by one of Sony's senior EE guys that it can be
>>> > baked into a glass master. As I understand it, jitter can be induced
>>> > any time the bits are clock-aligned for whatever reason. I'm not sure
>>> > why that occurs in making a glass master, but a lot of research was
>>> > done on this back in the 80s and 90s, at least that's my understanding
>>> > from what the Sony guy told me.
>>> >
>>> > So, I think (but may have learned this wrong, I'm not an EE) that bits
>>> > is bits only when the bits are kept absolutely intact and the
>>> > timing-transmission is rock solid.
>>> >
>>> An example of where jitter is not important is downloading a file from
>>> the web. The timing of arrival of the bits (which will be in packets) is
>>> not important, so long as they end up in the correct order in the file.
>>>
>>>
>>>
>>> Regards
>>> --
>>> Don Cox
>>> [log in to unmask]
>>>

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

March 2024
February 2024
January 2024
December 2023
November 2023
October 2023
September 2023
August 2023
July 2023
June 2023
May 2023
April 2023
March 2023
February 2023
January 2023
December 2022
November 2022
October 2022
September 2022
August 2022
July 2022
June 2022
May 2022
April 2022
March 2022
February 2022
January 2022
December 2021
November 2021
October 2021
September 2021
August 2021
July 2021
June 2021
May 2021
April 2021
March 2021
February 2021
January 2021
December 2020
November 2020
October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager