What is this defect called?

General questions or discussion about HandBrake, Video and/or audio transcoding, trends etc.
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gentleben
Posts: 24
Joined: Sun Feb 07, 2021 12:21 pm

What is this defect called?

Post by gentleben »

Movies are generally fine.
But on some older TV sitcoms from a few decades ago, the encoded videos sometimes show these weird colors:

https://ibb.co/X8d1D7B

https://ibb.co/zVrYGQ5
gentleben
Posts: 24
Joined: Sun Feb 07, 2021 12:21 pm

Re: What is this defect called?

Post by gentleben »

Sorry, I ended the post a bit early there. But what is the correct term for these colors? I can't research it because I don't know what it's called. And is there any way to get rid of those defects? Using deinterlace always on, Bob mode and FPS same as source (50fps) fixes it but loses quality elsewhere so is there any other way or is it just the consequence of encoding DVDs designed for TV? I think the designed for TV part must be relevant because movies designed for cinema don't have this problem. It's only the TV programmes (usually old ones).
Woodstock
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Re: What is this defect called?

Post by Woodstock »

For me, your links come up to pages with broken images.

How did you extract that video from the DVDs? Logs would tell us SO much more, which is why they're required.
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Ritsuka
HandBrake Team
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Joined: Fri Jan 12, 2007 11:29 am

Re: What is this defect called?

Post by Ritsuka »

1.4 will have a Chroma Smooth filter that could help with that, here's some info on it: https://github.com/HandBrake/HandBrake/pull/1957
nightly builds with the new filters are available to download on https://handbrake.fr/nightly.php
Lostless
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Joined: Thu May 24, 2007 7:55 pm

Re: What is this defect called?

Post by Lostless »

To answer the original question, it looks like a morie pattern mixed with chroma sub sampling. The high details don’t line up with the pixel grid and capturing color at 1/4 the resolution. If the image was scaled down, the pattern can be made worse, and compression only exacerbates it.
Lostless
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Joined: Thu May 24, 2007 7:55 pm

Re: What is this defect called?

Post by Lostless »

Also old analog tv had this issue as well. The pattern would show up as a minor rainbow pattern in the color signal in high frequency color patterns. Color on analog tv was also encoded at a lot lower resolution.
Lostless
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Re: What is this defect called?

Post by Lostless »

Final analysis. I think dvd is sub sampled per field. So lines 1&3 share color data and 5&7 share color data ect ect. On top of that you have lines 2&4 ect ect sharing color data. When played back properly deinterlaced, or on a analog tv, this is no big deal. It’s why bob deinterlacing is working properly, it’s extracting the proper color data for each field. When you encode using no deinterlacing, assuming that the source is a pure 25fps PAL or 30 ntsc, high frequency info (colors that change a lot in a small area) will just all mush together when made progressive and changed to a different color encoding. Low frequency info typically shares colors over large areas so the errors are less noticeable when changing color sub samplings.
Lostless
Bright Spark User
Posts: 155
Joined: Thu May 24, 2007 7:55 pm

Re: What is this defect called?

Post by Lostless »

Final analysis. I think dvd is sub sampled per field. So lines 1&3 share color data and 5&7 share color data ect ect. On top of that you have lines 2&4 ect ect sharing color data. When played back properly deinterlaced, or on a analog tv, this is no big deal. It’s why bob deinterlacing is working properly, it’s extracting the proper color data for each field. When you encode using no deinterlacing, assuming that the source is a pure 25fps PAL or 30 ntsc, high frequency info (colors that change a lot in a small area) will just all mush together when made progressive and changed to a different color encoding. Low frequency info typically shares colors over large areas so the errors are less noticeable when changing color sub samplings.
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