Bandwidth for comp. video switching?

Discussion in 'AV Receivers' started by seth_petry_john, Sep 10, 2004.

  1. seth_petry_john

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    I've been looking for a new receiver that will do component video switching. I've seen some models that claim 30MHz for compatibility with progressive scan DVD/DTV.

    I've seen other models that claim compatibility with "wideband (480p, 720p, 1080i)" signals, but no bandwidth listed.

    And then I've seen models that claim 100MHz for compatibility with HDTV.

    What's the deal here? If I'm intending on running my HDTV signal direct to my TV, and then using a receiver to switch between component video connections from Xbox and DVD player, will 30MHz be sufficient? Would I notice any benefit from higher end receivers that claim to support higher bandwidths?

    Note that some Xbox titles support 1080i resolution, so does this mean I need my receiver to support HDTV in order to not have picture quality issues when viewing those titles?

    FWIW, I've read http://members.aol.com/ajaynejr/whyten.htm a few times over but I'm still struggling to make sense of it all.

    Thanks for helping me get this straight,
    Seth
     
  2. Chu Gai

    Chu Gai Lead Actor

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    You need 3x the bandwidth of the source. If you're running 1080, the bandwidth is about 35 MHz so your switching device should be about 100 MHz.
     
  3. seth_petry_john

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    Do I need 3x the bandwidth for it to WORK, or just for it to work without looking like crap?

    And if 1080 is 35MHz, what is the bandwidth usage of a normal progressive scan 480p signal?

    Thanks!

    Seth
     
  4. ChristopherDAC

    ChristopherDAC Producer

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    NTSC [525/480i29.94 -- ordinary TV] is bandlimited to 4 MHz ceiling. NTSC from a LaserDisc is about 4.5 MHz, 480i30 from a DVD about 5 MHz, and 480p60 from a "progressive scan" deinterlacer is 10MHz although it doesn't contain any more information than the 480i signal. Thus the 30 MHz bandwidth for progressive-scan connexions. Since bandwidth of connexions is ordinarily measured at a 3dB rolloff, you can shove a 1080i30 signal through a 30MHz bus -- but it will be degraded in horizontal resolution and probably suffer various delay and phase-shift artefacts, i.e. "look like c--p". The reciever being simply a pass-through is very unlikely to simply refuse the signal altogether, but you might wish it had. [​IMG] In the worst case it could be so degraded that the TV will not recognise it.
     

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