Explain Progressive to Interlaced?

Discussion in 'Displays' started by Chad Ferguson, Jul 27, 2004.

  1. Chad Ferguson

    Chad Ferguson Supporting Actor

    Oct 31, 2000
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    These Rear Projection TV's i've been looking at all accept 720p and 480p signals, but converts it to 1080i. Does this kill the point of progressive? If I have an Xbox game that does the 720p will it look any better? Should I even bother buying a progressive DVD player? Can someone explain why this is done and if it's worth it?
  2. John S

    John S Producer

    Nov 4, 2003
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    Probably not....

    But that doesn't mean any given HDTV set will not perform better on one or the other.

    The eye has a very hard time telling the two apart as long as they are equivelent.

    480p and 960i should look identicle to the eye
    540p and 1080i would look almost identicle to the eye
    720p and if it existed 1440i should look nearly identicle to the eye.

    There probably is a better FAQ around here that explains it better than I am though.
  3. SimiA

    SimiA Second Unit

    Jul 26, 2004
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    The technical definitions are:
    Progressive Scanning is the process of re-assembling a picture from a video signals, all the horizontal scan lines are scanned on the screen at one time.

    Interlaced Scanning Refers to the process of re-assembling a picture from a series of electrical signals. The frame/picture is made up of two fields: The first field has a number of odd lines and the second field has the even lines. The odd lines are scanned on the screen in 1/60th of a second and the even lines follow in the next 1/60th of a second. This presents an entire frame/picture in 1/30th of a second.
    And yes, you should get a pro-scan DVD player.
    If you can afford it, get one with a Faroudjia chip.
  4. Allan Jayne

    Allan Jayne Cinematographer

    Nov 1, 1998
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    From the standpoint of the DVD player, the TV's converting the 480p (progresive) output to 1080i does not kill the point of progressive. Each incoming progressive frame is still 480 active scan lines and is converted to have 540 active scan lines.

    On the screen the difference between 540p and 1080i (or between 480p and 960i etc) is that, for the ---p the incoming video scans are treated as frames and superimposed while for the ---i the incoming video scans are treated as fields and every other one is staggered slightly downward. For DVD there is no distinction between "even" and "odd" at this point in the video signal path. Some TV sets may enhance the 480p to 1080i converted picture to make diagonals smoother, namely do some blending of scan lines.

    Depending on the fatness of the electron beam, you may think that one looks better than the other (if the TV gives you a choice, a few do) for DVD. For 1080i HDTV, superimposing and also the aforementioned blending loses quality.

    720p can pose its own problems. It is not readily apparent how the video is converted to 1080i, the simplest conversion methods use 540p as an intermediate step and such a downconversion loses resolution and renders the result non-hi-def.

    All current models of HDTV sets also accept 480i, also converted to 1080i (almost always with 480p as an intermediate step and much worse if not), so a progressive DVD player is not mandatory. On average, a progressive player will give a slightly better picture, but if the TV itself has a Faroudja or Silicon Image de-interlacing chip, the difference will be hard to see.

    Video hints:

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