Why are some PAL discs mastered with jaggies?

Discuss internationally-released DVDs, Blu-rays, and UHDs and related topics
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denti alligator
Joined: Thu Nov 04, 2004 1:36 am
Location: "born in heaven, raised in hell"

#1 Post by denti alligator »

I mean specifically the single jaggie at the top and the single jaggie at the bottom of the picture. Those with overscan won't have noticed this, but it's visible on a whole bunch of my PAL discs (though not on MoCs, thankfully). It's usually in the center of the screen (on the horizontal axis, that is). A recent example is on the Quay Brothers set where one film, The Phantom Museum, has this effect. It's very annoying. I usually zoom in a hair to hide it, but on widescreen pictures this isn't an option.

Does anyone know what causes this? I'm assuming this is also visible on native PAL systems. Sadly the Edition Filmmuseum DVDs have this problem, as do all Tartan discs.
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HerrSchreck
Joined: Sun Sep 04, 2005 3:46 pm

#2 Post by HerrSchreck »

I may be off here because I'm a little confused by your first saying it's at the top and the bottom of the pic, then your subsequent statement that it's in the middle, i e
I mean specifically the single jaggie at the top and the single jaggie at the bottom of the picture.
then
It's usually in the center of the screen (on the horizontal axis, that is).
But a couple of comments, as I think I know what you mean (center top & center bottom?) --

I have anamorphic controls on my MVL which allow me to view the edges of the transfer in all cases, and can say:

in the case of an analog source tape, the classic signature of this source material is a ragged jaggy bottom line. You can see this, for example-- if memory serves-- on the interview with Vlada Petric on the RUBLEV disc. Signaling that this interview was conducted on an analog vhs tape.

In the case of a digibeta, you may occasionally note what looks like-- in the exact same bottom position as the analog shag-- the silohuette of a thin black belt, complete with buckle... i e a black strip with a slightly off center square in it running the complete horizontal length of the screen. But I should say that, without the rare anamorphic controls mentioned above, one should have to zoom out to see this strip, whereas the shaggy analog bottom rot should be visible with little zoom-out.
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denti alligator
Joined: Thu Nov 04, 2004 1:36 am
Location: "born in heaven, raised in hell"

#3 Post by denti alligator »

Yeah, you got what I meant. Sorry to be so confusing. Yes, the center top and bottom.

On the Edition Filmmuseum disc of Enthusiasm, the film has these marks but the Kubelka docu doesn't. But surely the film was transferred from the original elements?

On all BFI discs the BFI logo screen has these marks, too.
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SoyCuba
Joined: Tue Jul 24, 2007 7:30 pm
Location: Finland

#4 Post by SoyCuba »

This is something has annoyed me for a while now. It may not be a huge thing, but it's certainly noticeable. I wanted to ask this especially from Nick, since MoC's transfers have avoided this problem in all cases (as far as I know) but one: Shoeshine. I don't have the disc myself yet, but the DVDBeaver review verifies this.

Look at the upper and bottom edge of the frame and you'll notice that they are both jagged (easiest to see in the second picture with the horses). What causes this? I only know this is something that occurs in 1.33 and anamorphic 1.66 and 1.78 PAL transfers. I must also ask that MoC would avoid this in their future releases.
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der_Artur
Joined: Mon Nov 08, 2004 10:22 pm
Location: stuttgart

#5 Post by der_Artur »

The cathode ray does not start at the far end of the first line of the PAL signal, but at the centre of this line. And it also ends at the centre of the last line. This is, if i remember correctly, to make the cathode ray switch from the bottom to the top easily. But it also results in an interrupted, i.e. jagged, signal at the very bottom and top of the picture.
peerpee
not perpee
Joined: Tue Nov 02, 2004 7:41 pm

#6 Post by peerpee »

It's possible to deal with it in the encode, if you spot it. I try to catch it whenever I see it, but occasionally they can slip through.
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