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Old 22nd January 2023, 17:12   #75  |  Link
MaximRecoil
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Join Date: Feb 2004
Posts: 192
Quote:
Originally Posted by Sharc View Post
The IVTC'd source is all progressive and basically judder-free with little remaining judder from the framerate (usually 23.976fps) and monitor refresh rate ratio not being an integer multiple.
Yeah, that applies to playing it on a PC, but on my BD player when outputting 480i, the output isn't progressive, it's 59.94 fields per second (the only progressive video that my CRT TV is even capable syncing to is 240p, but I don't have a video player that can output 240p, only old video game consoles), but it's still as judder-free as playing them on my PC. I don't know the exact process it uses to convert 23.976 frames per second progressive video to 59.94 fields per second interlaced video on the fly, I just know that it has to do it, because NTSC video is inherently 59.94 fields per second (originally 60 fields per second before they revised the standard in 1953 to accommodate color).

Quote:
I don't know how studios do it, but as I understand, downscaling will always have to be preceeded by low-pass filtering (softening the picture) in order to prevent aliases.
That's interesting.

The down-scaling from HD to SD definitely has something to do with the sawtooth effect, but there's more to it than just that. Like I said, for some reason my BD player exaggerates it while my WD Live TV player doesn't. Also, on my BD player, the piped-to-x264 encode I did showed even worse sawtooth than my plain IVTC'd encodes, and that was down-scaled in exactly the same way, i.e., the down-scaling was done in FFmpeg using the same script as with my plain IVTC'd encodes.

If there were a method to down-scale without introducing any aliasing (or less aliasing at least), I wonder if that would eliminate the issue; the idea being that there would be nothing for the BD player to exaggerate in the first place. If I remember right, Lanczos, which I always use, has a bit of a sharpening effect, which would also increase its aliasing effect. I could try just plain bilinear scaling to see if that makes a difference.

Last edited by MaximRecoil; 22nd January 2023 at 17:56.
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