Component Video Bandwidth for HDTV

Discussion in 'Playback Devices' started by HermannMasser, Sep 22, 2003.

  1. HermannMasser

    HermannMasser Auditioning

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    Hi,
    I have read many different opinions as to what is the minimum bandwidth rating on a component video Switch to pass HDTV signals, I was looking at the JX-S111 and found it only "passes" 30MHz and then I read different and contraicting opinions as to what is enough to pass HDTV signals, My questions are:

    1.- Would the JX-S111 would still pass an HDTV signal and what would be the effect knowing that it is rated at 30MHz? (i.e. degradation, etc)

    2.- What would be the minimum bandwidth that I look for on a component switch to ensure a good signal is passed?

    An alternative to the JX-S111 would be to get a new receiver and I found several units that would go from 50MHZ up to 80MHZ on component switching but I don't know if it is really worth the extra $$$$, also, along the same lines, I figured that If I get a good quality Component Switch and a decent AV switch (for my S-Video Signals)I would come very very close to buying a new receiver ($$$)....

    Any input would be greatly appreciated.

    FYI, I am using an Infocus X1 projector (2000:1 contrast ratio) on a 100" 4:3 screen, and unless the room is dark I can't really appreciate or notice any difference in signal quality, I only use my projector after it is dark....

    Thanks

    Hermann
     
  2. Don_Berg

    Don_Berg Supporting Actor

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    An HD video analog component signal has 37Mhz bandwidth (on the Y channel), but your display's own frequency response may be less than that. But to be certain that the video switcher doesn't soften the signal you should have somewhat higher than 37Mhz, 50Mhz+ is recommended if you have a good display.
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    This thread on Inexpensive HD Switching has a lot of discussion and links to various switchers.

    What a engineer would do is take the max frequency you expect to have (36 Mhz) and purchase cables/switchers that promise to have less than 3 db (50%) degradation of the signal at 4 times the frequency.

    This means you want something that will pass about 140 Mhz.

    Note: Yamaha receivers that accept HD video signals only use a 3X factor so they are rated for up to 100 Mhz.

    This 4 times overhead is because:

    - Sudden changes in the frequency will cause over-shoot/ringing that appears at 2x the highest frequency. You DONT want to cut these off as the display is expecting these.

    - Your entire band path is 4 RCA plugs and at least 2 runs of coax. Your switcher will add to this and you dont want it to be the weak link in the chain.
     
  4. Dave Miller

    Dave Miller Supporting Actor

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    Yeah, but is there a frequency difference in MHz between a 480p signal and a 1080i signal?

    I have a Denon AVR-3300 and it has two component inputs that pass a component video signal at 27MHz (-3db). My television only has two component high def inputs for me to run a video signal directly. If I get a HD STB, I would want to run the video signal from the STB directly to the TV since many of the HD channels are in 1080i, but will I loose signal quality by sending my progressive scan dvd player (at 480p) and / or my Xbox (most of my games are 480p) to my receiver first to do component switching? I realize I could buy a switcher, but I don't want to if technically 480p can be switched through my receiver w/o any signal loss.

    Any of you engineers know the answer to this?

    Peace,

    DM
     
  5. Don_Berg

    Don_Berg Supporting Actor

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    Yes - 480p requires 14Mhz bandwidth, whereas 720p or 1080i HD requires up to 37Mhz bandwidth (though some HD signals are filtered to reduce it a bit). By the way 480i requires 7Mhz bandwidth on component.
     
  6. Dave Miller

    Dave Miller Supporting Actor

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    Thanks Don.

    Peace,

    DM
     

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