2-hour length, 148.50 Mhz, 1920 x 1080 progressive scan image, 1-bit object data, 193 bits of file s

Discussion in 'Amateur Video Production' started by Radium, Oct 27, 2006.

  1. Can anybody explain what is the point of this whole
    "discussion"? It seems to me like one of the most
    ridiculous wastes of time that has come along here
    in months/years.
    Richard Crowley, Nov 2, 2006
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  2. Sorry, I was a bit short in my answer, but I understood what you said :)
    My bad.

    Martin Heffels, Nov 2, 2006
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  3. But this is a bit weird comparison. After all, a normal colour-image on tv,
    can not be represented by 1 bit pieces. It would be better to speak in
    terms of bytes, and then a compression-ratio makes more sense.
    When I am compressing an video-image, I am not throwing away 7 bits and
    keep 1. No, I throw away bytes which are occuring repeatedly (lossless), or
    similar in colour (lossy).

    Martin Heffels, Nov 2, 2006
  4. Radium

    Ken Maltby Guest

    Ken Maltby, Nov 2, 2006
  5. Radium

    Pasi Ojala Guest

    When someone else is doing video compression (btw, it not
    AN image, video compression handles multiple images), it is
    much more than that.

    There's delta coding (differences between frames), transform coding
    (for example DCT) and quantization (represent data that matters most
    more accurately). And/or prediction and encoding only prediction error.

    After this lossy phase you use lossless entropy codes.

    Pasi Ojala, Nov 2, 2006
  6. Radium

    Bob Myers Guest

    Doesn't matter whether you talk about bits, bytes, words,
    characters, or squamishes (a word I just stole from an old
    Mad magazine to refer to data organized in 43-bit chunks).
    You start out with this many bits, you wind up with this many
    bits. It's just that "average bits per displayed pixel" has been
    one of those fun ways of presenting compression ratio
    information, especially in seminars where the objective of
    the presenter is to elicit a "wow!" response from the audience
    which is presumably learning about this stuff for the first time.

    And you're never simply throwing away bits or bytes in
    any practical compression scheme which is currently in
    use; that would be far too crude. What happens in real-
    world systems is far more complicated, and produces a
    far better result.

    Bob M.
    Bob Myers, Nov 2, 2006
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