Jitter and DVD/CD players (SACD, DVD-A)

Discussion in 'Archived Threads 2001-2004' started by Kevin C Brown, Sep 4, 2001.

  1. Kevin C Brown

    Kevin C Brown Producer

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    Just wondering what the community out there thinks.
    Does jitter matter? Or better stated, does jitter matter in any other context other than any effect on a typically measured parameter such as freq response, linearity, signal to noise ratio, etc.
    And if it does, why don't any of the (major U.S.) home theater mags report it as a test criteria?
    Not SGHT, not WSR, not S&V, not Home Theater magazine, not the Sensible Sound, not the Audio Critic, not the Secrets web site www.hometheaterhifi.com (who in my opinion, do the best testing of DVD players anywhere. They found the "chroma bug," after all.), and not Audio magazine or Stereo Review in the past, or even High Fidelity before that?
    (Anybody know about the Perfect Vision?)
    And at least one article I read says that jitter is even more critical in DVD players because of their higher data rates.
    And, I have seen that Stereophile does report jitter measurements, and supposedly correlates them to sound quality, but if it really mattered, why doesn't SGHT report them? Especially if it's more critical for DVD players, which is more up SGHT's alley than CD players, which are more up Stereophile's alley?
    It's the same big group of people who publish both those mags.
    And, even more especially, since it is well known that it much easier to detect deviations from 2 different signals in video (with your eyes, i.e., DVD) than in audio (with your ears for CD).
    Just curious...
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  2. RicP

    RicP Screenwriter

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    i'll try and make this concise. [​IMG]
    Basically Jitter is really only a concern when you are running a digital stream from a transport to a decoder. Video is not affected because it's analog, and neither is analog audio.
    DVD and Home Theater really isn;t affected because Dolby Digital and dts are "packeted" data streams, meaning they are not decoded real time and synced to clock cycles. They are more analagous to computer data rather than audio.
    Jitter is a concern when you are using a CD/DVD Player as a transport and sending the PCM data on a digital cable to an outboard DAC or reciever. Because the clock in the transport may not be exactly in line with the clock in the destination, there can be small timing errors.
    For more info see http://www.jitter.de
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    http://www.ricperrott.com
    Ric Perrott - My DVD's
     
  3. Saurav

    Saurav Cinematographer

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    RicP summed it up pretty well. There is another angle to this argument - no one really knows how much jitter is audible, or visible, for that matter. There is little data and lots of speculation, so I can see how a magazine would decide it's not worth their time to test/report this data.
     
  4. Kevin C Brown

    Kevin C Brown Producer

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    Great info. (It will take me a while to get through that site!!)
    I didn't know that DD and DTS were not affected because of how those signals are encoded.
    And, I did a brain fart on (analog) video.
    So only CD transport.
    I know a dude who swears that a jitter number above 100ps (or something) is audible. But I think he's just parroting Stereophile numbers.
    And at least one other article I read, by a designer at Analog devices, said you have to be careful about how you measure jitter in that the measurement itself can be confusing. (You have to know what you're doing, in other words, and most equipment reviewers I *wouldn't* put into that catagory. Sigh.)
    I'm just trying to figure out if there'd be any merit to getting a "anti jitter device" for in between my DVD player and pre/pro.
    But then again, I'm waiting for a (good, cheap) SACD/CD combi player anyway, and then I'll just use analog passthrough and won't need it anyway!
    Thanks! (My donation to HTF is paying off already!!)
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  5. StaceyS

    StaceyS Stunt Coordinator

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    We, Secret's, don't have the Paul Miller Jitter Measurement system to measure jitter like Stereophile does. I have been trying to get one, but the sound card used is no longer made. To get that system now requires the purchase of the full Miller suite, which is a bit expensive. [​IMG]
    I would love to include jitter measurements at some point. The AP is supposed to measure jitter, but no one seems to trust its results.
    The comment on jitter with higher data rates would fit more with SACD and DVD-A, not to DVD films.
    Some of the UK mags provide jitter numbers. Of course Paul Miller is the one doing the writing in most cases.
     
  6. Saurav

    Saurav Cinematographer

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  7. Kevin C Brown

    Kevin C Brown Producer

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    >>>
    I'm just trying to figure out if there'd be any merit to getting a "anti jitter device" for in between my DVD player and pre/pro.
     
  8. Kevin C Brown

    Kevin C Brown Producer

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    Ok, the quote in the above should have been:
    >>>
    Easy way to test that is to borrow one from somewhere/get one on trial, and see for yourself.
     
  9. Henry Carmona

    Henry Carmona Screenwriter

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    Location:
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    Real Name:
    Henry Carmona
     
  10. Kevin C Brown

    Kevin C Brown Producer

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  11. Saurav

    Saurav Cinematographer

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  12. Kevin C Brown

    Kevin C Brown Producer

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    I read through the entire "jitter.de" site. This Jisco thing might actually be the greatest thing since sliced bread. [​IMG]
    And I looked through the "digital" part of audioasylum, and everyone who tried it liked it very much. Hmmm...
    An "audiophile enhancement device" with some seemingly scientific engineering involved. Imagine that!
    And now, I have a hankering for the "Secret's" site to take a look at this thing too...
    ... "Why can't I have it all?" ...
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  13. Saurav

    Saurav Cinematographer

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