Component output on-screen disply

Discussion in 'Archived Threads 2001-2004' started by brian a, Feb 20, 2002.

  1. brian a

    brian a Second Unit

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    I understand from the 950 thread that most units that do component video switching do not offer on-screen display on that output. The explanation I've gotten is that it effects picture quality. What I don't understand is why this effect is greater than it would be on s-vid or composite. Is component a lower bandwidth medium? Also is bandwidth reserved for OSD on an output even when it's not in use, or would the effect be noticeable only when the menu is on screen?

    brianca..
     
  2. Greg_R

    Greg_R Screenwriter

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    Component video is the best quality format switched by the receiver. To add the OSD the signal needs to be routed through additional circuitry. This circuitry introduces (potential) distortions. Since S-video and Composite are lower quality anyway, we don't care about taking a slight hit on picture quality with these formats. After all, if we wanted the best picture we'd be using component video anyway...
     
  3. brian a

    brian a Second Unit

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    Ahh. That makes more sense. It's the additional pathing through the unit that could cause the loss. Not the adding of OSD material itself. So it's a matter of improving that circuitry to handle the bandwidth and dataflow of the component feed. I imagine I'm not the only one who no longer has any non-component video sources. DVD, STB, X-BOX.

    brianca.
     
  4. brian a

    brian a Second Unit

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    What are the bandwidth limits on composite vs. s-vid vs. component?

    Are there any links someone can provide on more details of the circuitry?

    brianca.
     
  5. Allan Jayne

    Allan Jayne Cinematographer

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    The most demanding NTSC source material commonly encountered using composite (is interlaced only) or S-video (is interlaced only) is DVD; the bandwidth required is just under 7 MHz for the approximately 720 pixels across. If the bandwidth of the circuitry is less, which it usually is, picture details can still be centered on any one of the 720 possible positions but they will be less sharp as in not being able to be as narrow as 1/720'th the screen width.
    Component video for DVD, from an interlaced player output, also goes up to just under 7 MHz.
    The most demanding source material standardized for component video is 720p HDTV, requiring 37 MHz video bandwidth for 1280 pixels across. 1080i requires 37 MHz for its 1920 pixels across but so few TV sets can make spots smaller than 1/1300'th the screen width (one and a half, or 3/2, times the pixel size) so we can get by with 2/3 the bandwidth, or 25 MHz for 1080i.
    More:
    http://members.aol.com/ajaynejr/bandwid.htm
     

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