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  1. Hi,

    I am doing my own conversion of The Animatrix shortcuts and trailer from desktop to anamorphic SVCD.

    I have read several times how one should tweak the contrast and gamma when converting the oposite way, that is, encoding from TV source to content intended to be watched on a desktop computer, to avoid washed out colors and grayish blacks.

    I'd appreciate any comments and suggestions on appropiate hints when converting from source intended for desktop watching to TV, since, if not, I guess, it will appear quite darker in the TV than intended.

    The same goes for audio. Does PC "normal" audio volume equals TV "normal" audio volume?
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  2. Member DJRumpy's Avatar
    Join Date: Sep 2002
    Location: Dallas, Texas
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    If you video is already in PC format (using 255 luminance levels), then the damage is already done. When you convert it to MPEG, it will squash the luminance level for you, to 235 luminance levels. Chances are, you probably won't even notice. It tends to make your whites whiter (just like laundry detergent ), and your darks 'sparkle' in low motion scenes.

    Don't worry about the audio. The conversion does sometimes drop the audio by a small amount. Again, you probably won't even notice. A simple tweak of the volume knob will solve any discrepency if you do.
    Impossible to see the future is. The Dark Side clouds everything...
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  3. If you video is already using 255 luminance levels then the damage is already done.
    Could you please expand on that? I do not understand how having a wider range of luminance in the source prevents any sort of possible correction (if it was the opposite...).

    When you convert it to MPEG, it will squash the luminance level for you, to 235 luminance levels
    Do you mean MPEG-2 (what about MPEG-1?) cannot have 255 levels and thus it will force that downgrading wether or not I took it into account? And how does it do it, does it scale the luminance range down (making pure black a little less dark, but darker to a, for instance, RGB(1,1,1) black, which I guess would be the way to go, or does it simply cut those 20 extra levels off, flattening all dark & bright details?

    Wouldn't it be better to manually adjust it just before compressing? If so, what values of which factors would you use?

    It tends to make your whites whiter and your darks 'sparkle'
    The intention of the question was, in the end, how to avoid these things...
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  4. Member DJRumpy's Avatar
    Join Date: Sep 2002
    Location: Dallas, Texas
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    A television set can only display 235 luminance levels, where a PC can display 255. When a file is converted to digital format, if the person doing the converting was not careful, you end up with a file containing PC luminance levels (255), instead of television (235), or, even worse, the person encoding can select the wrong input luminance level (telling the encoder it has 255), indicating the encoder should encode for TV luminance levels. It will then 'squash' the luminance level to fit in 235. It makes your bright colors look washed out, and it makes your dark black area's 'sparkle' with gray macroblocks. They look like digital noise. Once it happens, there's not much you can do to fix it, other than darkening your video to eliminate the sparkles, but it will be overall darker than it should be.
    Impossible to see the future is. The Dark Side clouds everything...
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