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Question about video up-conversion.

Discussion in 'Archived Threads 2001-2004' started by Vincent_S, Feb 8, 2003.

  1. Vincent_S

    Vincent_S Second Unit

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    If a receiver has this function, does the receiver have to be powered on or can it be in stand by mode? I am looking at the Sony da2es and da4es at the moment.
     
  2. BrianWoerndle

    BrianWoerndle Supporting Actor

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    You will have to have the power on. The internal circuits are doing the switching as well as the converting.
    What would be the point of upconverting a video signal with it off?
     
  3. Vincent_S

    Vincent_S Second Unit

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    Because I would only want to watch a recorded show with audio from the TV but still have S-video picture. Am I not understanding something about this function?
     
  4. BrianWoerndle

    BrianWoerndle Supporting Actor

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    The upconversion function is only for convience. If the signal started out life in composite, it will never get any better. Think of an egg, It starts with a yolk and a white. The yolk can not get through the wire, so it has to be scrambled together until it is thin enough to go through the wire. The receiver will never be able to get the entire yolk back. All it can do is send the scrambled mixture through a S-Video wire. I don;t even understand how it odes it, but it works. But the signal is no better. The upconversion is only a means to send it through the S-Video wire for the convience of not having to change inputs on the TV.

    Using TV speakers? Yikes. I will never turn on my TV's speakers again. You can use your receiver for everything, so why not take advantage of the better sound? Then you can have the conversion too.
     
  5. TimTurtino

    TimTurtino Stunt Coordinator

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    A video signal (for the purposes of this discussion) has two components -- luminance (Y: how bright it is at a particular point-- the black and white componennt), and chrominance (C: what color it is at the point).

    W/ the standard RCA or composite video connection, the luminance and chrominance are sent at different frequencies-- kind of like sending the B&W pictures at 95 FM, and the color signal at 97FM. The TV has to separate out that info, in order to paint the picture correctly. Unfortunately, as you might guess from the radio analogy, it's not always perfectly possible to do the separation (for much the same reason that you sometimes hear a strong station on nearby bands). The circuit that does this separation in (all but the cheapest) TVs is called a comb filter. Now, the circuit that does this separation in the receiver is most likely a rudimentary one called a bandpass filter (for instance, in the Onyo 800 manual, it specifical refers to the "simple Y/C separate circut" which does that job, so I'm assuming it's not a comb filter), which doesn't do nearly as satisfactory a job. Going the other way (combining the Y & C info from the S-Video onto the composite wires) is trivial, and only causes the same problems that are always associated w/ composite video. But think about this--

    If you leave the composite signal alone, the (probably much better) comb filter in your TV will do the Y/C split. If you upconvert it to S-Vid, then the TV's comb filter will never see the signal, and so you'll be at the mercy of the receiver's (probably much worse) filter, and so will see artifacts on a big enough screen.

    Upconversion is convenient and can solve some problems, but it's a mixed blessing,

    Me

    P.S. -- Basically, what Brian said is right on the money, except for the fact that the picture can actually be worse after upconversion, due to the receiver's much worse filter doing the Y/C split. And I totally agree w/ him about audio-- unless you have a cheap HTIB and a really great sounding TV, your stereo will always sound better than your TV.
     
  6. Vincent_S

    Vincent_S Second Unit

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    I know my stereo sounds much better than my TV speakers, although my TV speakers aren't too shabby, but I'm really not interested in watching "The King of Queens" through my Def Techs.[​IMG] BTW, I've decided to leave things as they are and not "up-convert".
     
  7. terence

    terence Supporting Actor

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