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  1. So all pro's for QTGMC.
    I believe what forums say and using it instead of Yadif.
    But what are downsides of QTGMC in short?
    Thanks.
    Last edited by taigi; 2nd Jun 2021 at 01:29.
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  2. Member
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    The downside s that it is much slower
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  3. QTGMC is not a deinterlacer, it's a script, that actually uses Yadif for deinterlacing when you choose the ultrafast or superfast presets.
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  4. Choosing high presets - up to Placebo.
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  5. Originally Posted by taigi View Post
    But what are downsides of QTGMC in short?
    It depends on how you are using it, and what your goals are

    One drawback is it tends to denoise or smooth over fine details . It's the reason for it's precursor's existence - calming bob flicker, reducing aliasing . Sometimes that's considered a "pro", sometimes a "con" in some situations

    Other than slow, it requires many prerequisite functions and plugins
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  6. It looks like I noticed extensive smoothing.
    What could be the way to lose less of fine details?
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  7. Originally Posted by taigi View Post
    It looks like I noticed extensive smoothing.
    What could be the way to lose less of fine details?


    Read the detailed instructions, especially the source match, noise bypass, GrainRestore, NoiseRestore sections .

    In general, higher temporal radius (TR0,TR1,TR2) settings, means more smoothing thus more loss of detail

    There is a lossless mode which retains the original fields, but then you get more flicker, shimmer, combing and less smoothing.

    There are many settings you can adjust, all of them are tradeoffs. Preview your results (e.g avspmod), and tweak them.
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  8. Downsides?

    1. Using it when it's not called for (double-rate deinterlacing when an IVTC is called for, for example).
    2. Slow (I usually use a much faster and nearly as good bobber).
    3. Using it mostly for its cleaning properties (I prefer using dedicated filters for cleaning).
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  9. Originally Posted by manono View Post
    Downsides?

    1. Using it when it's not called for (double-rate deinterlacing when an IVTC is called for, for example).
    2. Slow (I usually use a much faster and nearly as good bobber).
    3. Using it mostly for its cleaning properties (I prefer using dedicated filters for cleaning).
    +1, especially #1. Too many people read about QTGMC and think it is some sort of magic plugin. Although it has nice features, it is not magic. In addition, unless deinterlacing is required for subsequent operations, you should just leave the video interlaced and let your TV set handle it. Modern TVs do a fine job of deinterlacing, possibly even better than QTGMC, and certainly no worse.
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  10. Video Restorer lordsmurf's Avatar
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    User error, mostly. Lots of options.

    I've come across situations where any QTGMC setting would cause weird motion issues.
    See this: https://forum.videohelp.com/threads/398713-QTGMC-image-vibration-motion
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  11. Originally Posted by johnmeyer View Post
    Modern TVs do a fine job of deinterlacing, possibly even better than QTGMC, and certainly no worse.
    Wrong.

    The majority of TV sets do something similar to a bob deinterlace. They are definitely worse overall.

    High end sets have advanced additional processing and motion adaptive algorithms similar to QTGMC
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  12. Originally Posted by poisondeathray View Post
    Originally Posted by johnmeyer View Post
    Modern TVs do a fine job of deinterlacing, possibly even better than QTGMC, and certainly no worse.
    Wrong.

    The majority of TV sets do something similar to a bob deinterlace. They are definitely worse overall.

    High end sets have advanced additional processing and motion adaptive algorithms similar to QTGMC
    We are in agreement, I think. Those people who own low-end sets are not the people who are going to be wanting to use QTGMC because, being part of the "unwashed masses," they don't know interlacing artifacts from a hole in the wall.

    By contrast, people like me, and you, and most of the members of this forum who all care about this stuff, own decent TV sets that have excellent deinterlacing built in which, as you point out, do much the same thing as QTGMC, In fact, they probably do it better because they have direct access to the pixels on the screen.
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