What's Digital and What's Analog

Discussion in 'Archived Threads 2001-2004' started by Brent Hutto, Aug 10, 2002.

  1. Brent Hutto

    Brent Hutto Supporting Actor

    Aug 30, 2001
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    Let's say you're watching a Toy Story DVD on a direct-view HDTV monitor. It's my understanding that the Toy Story movies were created and the DVD's mastered completely in the digital domain, so it would be safe to say that up until the point where you bring the DVD home the movie has so far always been represented by digital codes. I also understand that the signals modulating the light beam illuminating the screen are analog in nature.

    So my question concerns how many times does that picture go back and forth between digital and analog representation. I'll further specify that you're using component video cables and a progressive-scan DVD player, although a second question is about the difference in that and a regular 480i-output player.

    So is the 480p signal that comes out of the DVD player and travels down the component cables analog or digital? I figure it must be analog so there's a D-A step right there.

    Then the HDTV monitor will digitize it to do whatever upconversion and so forth it needs to get to its native resolution. That's an A-D step there.

    Finally, the monitor has to generate analog signals to drive the CRT. That's another D-A.

    In real world, are there more A-D and D-A operations than this? How about if you use a regular old interlaced DVD player, does that effect how many conversions between digital and analog domains?
  2. Bill Slack

    Bill Slack Supporting Actor

    Mar 16, 1999
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    The TV shouldn't need to convert the analog input to digital and then back to analog to display. It should be able to route that analog signal directly to the CRTs. In the case of up or side converting (480i-480p, or 480?-540p, etc.) then it is necessary to have another layer in there.
    That said, many TVs might do it anyway.
    Take the old model Toshibas as an example. The built in method to the TV to display non-anamorphic material is a raster expansion, and to display 4:3 material, the TV can-not but bars on the side 'correctly', it just squeezes the picture, and causes severe geometry problems. My assumption here is that everything is kept analog. However, when upconverted, it must be capturing the frame information in a buffer and re-outputting it, and it also can add gray bars and re-adjust the picture size without changing the raster size, so I assume, at this point, there there must be an extra A/D->D/A process going on.
    I don't think the extra step on the set has any perceivable quality loss, however.
    Keep in mind this isn't researched though, and is just me assumptions and understandings. Your other assumptions are quite correct. HD and progressive via component cables are 100% analog. And no matter what, if you're looking at it, you can bet it's analog! [​IMG]

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