component switching bandwith

Discussion in 'Beginners, General Questions' started by Curt H, Dec 31, 2004.

  1. Curt H

    Curt H Auditioning

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    I notice there is quite a difference in what different manufacturers call HD quality component switching. Some have 50MHz some 80 some 100. My question is if I have HD satellite, progressive scan dvd,progressive output on the X box and want to switch them all through a A/V unit how much bandwidth is really necessary to accomplish this without degrading the signal?
    Thanks, Curt
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Short Answer: 90 Mhz or more

    Long Answer: Engineers tend to spec parts that can handle 3-4 times the maximum expected frequency.

    Component Video (480i): 4 Mhz max
    Progressive Video (480p): 12 Mhz Max
    HD Video (720 & 1080): 35 Mhz Max

    So a receiver that has 50Mhz bandwidth would be good for up to progressive video.

    You can also get external video switchers that do a great job: Inexpensive HD Video switching
     
  3. Curt H

    Curt H Auditioning

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    Component Video (480i): 4 Mhz max
    Progressive Video (480p): 12 Mhz Max
    HD Video (720 & 1080): 35 Mhz Max

    So the advertised 216,108,54Mhz processing is not related to the output of the signal in bandwidth?

    It seems I could safely switch my DVD player 480p and xbox also 480p and run the satellite independently with 50Mhz, yes?
    I have 2 HD component inputs on my tv plus DVI but the components look better than the DVI?? [​IMG]
    Thanks, Curt [​IMG]
     
  4. Bob McElfresh

    Bob McElfresh Producer

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    There is no "HARM". But while 50 Mhz bandwidth is fine for 480i/480p, it's not really enough for the HD sat video.

    Suggestion: Run the DVD player, XBox through the receiver. But feed the HD Sat system directly to the TV. Yes, it's a little bit more switching to use, but not that bad. (Hint: a universal remote with Macro feature can give you 1-button switching).
     
  5. Curt H

    Curt H Auditioning

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    Yes that is exactly what i was thinking. Run the XBox and DVD through my A/V and the HD sat directly to the TV. I have been dabbling with my HT for some years but had not paid much attention to the switching limitations of my receiver until I upgraded to HD sat and bought a new DVD player. Until recently I was running everything through the AV and the Satellite to my DVI input on the TV. I just started looking into upgrading after I got into the forum that led me here Audioholics. At that point I Bi-amped my system test drove a couple of different dvd players with up-conversion and sacd capabilities. It was then I noted the hazy washed out picture i got through the DVI connection compared to the component inputs etc. My question about 216,108,54 was directed at the dvd players and I should have been more specific sorry about that. Should have read 216MHz 12or14bit,108MHz 12bit and 54MHz10bit. So as it is right now I will return to switching my Xbox and DVD Via the AV and go direct with the HD sat to the TV. Thanks again for your detailed reply I feel more confident of not having to replace my AV unit for some time now.
    thanks again Curt

    My current system as of now.
    Onkyo TXNR 900 Bi amped w/3 Onkyo M282's
    Onkyo DVCP 802 6disk SACD/DVD-A 7.1 multichannel out[​IMG]
    Dish 811 HD receiver
    Sony XBR40-800
    Mstr HTS5000 pwr center
    Polk CS1000p center
    Polk Rt55i Left and Right front
    Polk Fx1000 (x4) surrounds and rear surround
    Velodyne CT150 and one CHT 15 for subs
     
  6. Allan Jayne

    Allan Jayne Cinematographer

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    >> Component Video (480i): 4 Mhz max*
    >> Progressive Video (480p): 12 Mhz Max
    >> HD Video (720 & 1080): 35 Mhz Max

    These are the video bandwidths needed for the entire video signal path in analog video. It so happens that when different components and cables each with the above rated bandwidth are connected together, the complete system bandwidth is almost always less, and the degradation is impossible to compute or predict without test equipment. So two and a half to three times the above bandwidths are often promoted as ballpark desirable figures for each component or cable.

    More:
    http://members.aol.com/ajaynejr/whyten.htm

    * For NTSC broadcast quality. For DVD it is 7 MHz
     
  7. Curt H

    Curt H Auditioning

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    Why is it that my HD signal looks better over component cables than through the DVI interface? Or should i start a new thread for that question?
     
  8. Allan Jayne

    Allan Jayne Cinematographer

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    >> Why is it that my HD signal looks better over component cables than through the DVI interface?

    1. The amount and kind of massaging (which may include upconversion or downconversion) the signal goes through may differ for the (analog) component video path compared with the DVI signal path.

    2. It may look better to you even though technically as measured by test equipment it is not.
     
  9. Curt H

    Curt H Auditioning

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    I just noted that the DVI input gave me picture that was apparently equal in detail but the colors were not as vivid. It was not too noticeable until i happened to switch my DVI cable and started using component cables. When I reconnected the DVI cable and switched between them outputting the same source at the same time then i could see it.
     
  10. Bob McElfresh

    Bob McElfresh Producer

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    You have discovered something: your display device needs to use separate calibration settings for each input.

    With your component cables, your television is taking 3 analog signals of some voltage and processing it internally. You have a BUNCH of brightness/contrast/hue/focus/... settings for that analog input.

    Now you hook up the DVI interface. This input has an entire, separate set of electronics and a separate set of settings and my guess is you have not re-calibrated this input so that it looks the same.

    There are people called "ISF Calibrationists" that will come spend 3-4 hours and adjust your television so that:

    - All the inputs are adjusted to produce the same color/brightenss
    - The colors/brightness all conform to a standard

    Or you can try it yourself with a copy of the Avia or Video Essentials DVD.
     
  11. Curt H

    Curt H Auditioning

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    Is that something that has to be done on some internal menu other than the user menu? I have made many different adjustments but it seems that the color,hue,contrast etc, setting is the same for all inputs once adjusted.
     
  12. Bob McElfresh

    Bob McElfresh Producer

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    It depends on the model of the televion.

    Some units use 1 set of user-setable settings for all inputs, and a service menu is used for individual setup.

    Other televisions even have separate use-setable settings per input.

    I would be suprised if your unit did not at least have separate settings for the DVI input. Check your manual.
     
  13. Jason=R

    Jason=R Auditioning

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    This isn't necessarily true. It all depends on what type of bandwidth numbers manufactures are quoting.
    Typically it is the -3dB bandwidth, which is the point at which you have lost roughly 1/3 of the signal content at that frequency. Since this says NOTHING about at what frequency the signal STARTS to be attenuated, people often just use some "rule of thumb" like 3-4 times the max frequency of the signal. They are assuming that if the -3dB bandwidth is high enough, that the frequencies that matter (~30 Mhz and below for HD) will have no loss.

    Here is a better way to really know the answer. Ask the manufactures for what the -0.1dB bandwidth of the product is. If that number is above ~30Mhz, HD will have no signal loss. If they don't know, don't count on it having no loss.

    Of course, you can also bring up the point that most people can't see -3dB loss in high frequencies unless it is pointed out to them.
     

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