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  1. Member
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    I've done this many times, because quite a number of years ago, the only capture devices on the market capped out at 1080i. The temporal resolution of the video was 60 images per second (video game footage), but of course the interlaced video I was capturing was 30 interlaced frames per second. But once I pass that captured video through a deinterlacer such as QTGMC, what I end up with is 60 progressive frames per second video. Furthermore, because QTGMC is so good at what it does, said progressive video is indistinguishable from a true 1080p60 video capture.

    Now. I happen to be discussing this matter with another fellow. He insists that it is impossible to render a 60 progressive frames per second result from interlaced video, that it is impossible to conjure the missing data from thin air, and seemingly that the interlaced video even contains a 60 images-per-second temporal resolution. He firmly believes that the only thing that could ever be rendered from interlaced video is either 24 or 30fps. Bearing in mind that I have countless specimens of deinterlaced video at 60 progressive frames per second which betray the inaccuracy of this assessment, what do the experts here think? Is he right?

    How about if a modern digital TV receives 480i or 1080i whose temporal resolution is 60 images per second (i.e. not a 24fps movie, but a 60fps soap opera). When the TV deinterlaces this video for displaying, is it rendering 60 frames per second, or is he once again right and the TV is discarding half of the frames and providing only 30 fps?
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  2. You're going to run into this a lot. Because interlaced video in the US is 30 frames per second, people end up believing that that is the final word on the frame rate, even after de-interlacing. It is a super-common misconception. You can't be surprised when you encounter people like this. Just ignore them and move on.
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  3. Originally Posted by Asterra View Post
    Is he right?
    No.
    When the TV deinterlaces this video for displaying, is it rendering 60 frames per second, or is he once again right and the TV is discarding half of the frames and providing only 30 fps?
    All modern NTSC televisions display 60 progressive frames per second (actually 59.94fps). So, if your friend actually "insists that it is impossible to render a 60 progressive frames per second result from interlaced video", then he doesn't understand what televisions do, or what double-rate deinterlacers such as QTGMC do. In cases where the original framerate is less (as with films), frames get repeated. In the case of a 24fps movie being shown on television, the frames get repeated in a 323232 pattern to bring the displayed framerate up to 60fps. When the source is true interlaced video, a television bobs it (but perhaps not as well as QTGMC) to output 60 unique and distinct frames per second (no repeats).

    What started out life as a field gets converted to a full frame by interpolation (often using bits from the neighboring fields) to fill in the missing video data.
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  4. Member Cornucopia's Avatar
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    Your friend is only right in the assertion that 60i to 60p must entail some amount of interpolation.
    Doesn't mean it can't be real good quality, maybe even fooling some to think it is equivalent.

    Scott
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  5. aBigMeanie aedipuss's Avatar
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    depends on your definition of impossible. re-encoding 60i to 60p requires the encoder to guess at 50% of the video image. not my cup of tea but some can live with it.
    --
    "a lot of people are better dead" - prisoner KSC2-303
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  6. Originally Posted by aedipuss View Post
    depends on your definition of impossible. re-encoding 60i to 60p requires the encoder to guess at 50% of the video image.
    It's often much less than 50 percent. Even fairly simple deinterlacers keep both fields in non-moving parts of the picture.

    And in the end, the video has to be deinterlaced for you to view it. QTGMC's deinterlacing is better than any TV or other hardware can deliver -- so why not use it? Yes, if you have very important interlaced video archive an intact copy of it. Someday something even better than QTGMC may be available.
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