An anti-alising problem? at DVinfo.net

Juni Zhao · October 16th, 2007, 10:33 PM

I have made a few DVD releases but one thing puzzles me: in the final DVD version the picture looks like lack of anti-aliasing. If there is a diagonal line it looks jagged. I thought it was just because of the nature of interlacing video. But why normal interlaced TV programs don't have this artifacts?
Would that problem be gone if I shoot 30f? I always have been shooting 60i so far.

Daniel Ross · October 17th, 2007, 12:55 AM

Many possible answers from any part of the process. Progressive might help... really depends.
Post a still.

Pedanes Bol · October 17th, 2007, 11:06 AM

As far as I know, jagged diagonal lines are compression artifacts. You may want to use a different compression method.

P.

Daniel Ross · October 17th, 2007, 12:56 PM

As I said, post a still, as there are many explanations.

both above are valid, but can't both be the solution, so you're just randomly tossing out guesses.

If it's the compression, nothing will help before that because compression is the last step, etc.

Juni Zhao · October 18th, 2007, 01:51 PM

yes, I will post a pic later, I have to use camera to take a snapshot from the TV.
But I did a test last night, I hooked up my camera to the TV directly, the result was almost the same, that means, it's not the compressor problem. I tried 30f SD, it was even worse, the artifacts were more visible, and framerate was jittery. I also test HDV, that was smooth. What is wrong with this SD feature? I use Canon A1. Seems A1 has lousy SD capability. Maybe from now on I should shoot HDV only and scale down to SD when I need only SD footage....

Juni Zhao · October 21st, 2007, 08:52 PM

http://channeldv.com/public/mpg2compressed.JPG

this TV screen snapshot was taken from DVD version.

http://channeldv.com/public/uncompressed.JPG

This was taken from a TV that was hooked directly to the A1 camera.

So what is wrong with Canon A1 SD? When I hook up with this camera with HDV everything looks nice and smooth,....

Seun Osewa · November 4th, 2007, 11:16 AM

Near horizontal lines look like that on my camcorder too.
I think it's a by-product of interlacing and in-camera sharpening.
I wouldn't worry about it too much; there's nothing you can do.

Normal interlaced TV programmes do have this artifact, but
people dont even see such things unless they're looking for them.

Glenn Chan · November 4th, 2007, 01:59 PM

It could be that your TV introduces scaling artifacts.

October 16th, 2007, 10:33 PM	#1
Juni Zhao Regular Crew Join Date: May 2007 Location: North Andover, Ma Posts: 102	An anti-alising problem? I have made a few DVD releases but one thing puzzles me: in the final DVD version the picture looks like lack of anti-aliasing. If there is a diagonal line it looks jagged. I thought it was just because of the nature of interlacing video. But why normal interlaced TV programs don't have this artifacts? Would that problem be gone if I shoot 30f? I always have been shooting 60i so far.

October 17th, 2007, 11:06 AM	#3
Pedanes Bol Regular Crew Join Date: May 2007 Location: Boston MA Posts: 167	Compression Artifact? As far as I know, jagged diagonal lines are compression artifacts. You may want to use a different compression method. P.

October 17th, 2007, 12:55 AM	#2
Daniel Ross Major Player Join Date: Jul 2007 Location: Marin & Davis, CA, USA Posts: 418	Many possible answers from any part of the process. Progressive might help... really depends. Post a still.

October 17th, 2007, 12:56 PM	#4
Daniel Ross Major Player Join Date: Jul 2007 Location: Marin & Davis, CA, USA Posts: 418	As I said, post a still, as there are many explanations. both above are valid, but can't both be the solution, so you're just randomly tossing out guesses. If it's the compression, nothing will help before that because compression is the last step, etc.

October 18th, 2007, 01:51 PM	#5
Juni Zhao Regular Crew Join Date: May 2007 Location: North Andover, Ma Posts: 102	yes, I will post a pic later, I have to use camera to take a snapshot from the TV. But I did a test last night, I hooked up my camera to the TV directly, the result was almost the same, that means, it's not the compressor problem. I tried 30f SD, it was even worse, the artifacts were more visible, and framerate was jittery. I also test HDV, that was smooth. What is wrong with this SD feature? I use Canon A1. Seems A1 has lousy SD capability. Maybe from now on I should shoot HDV only and scale down to SD when I need only SD footage....

October 21st, 2007, 08:52 PM	#6
Juni Zhao Regular Crew Join Date: May 2007 Location: North Andover, Ma Posts: 102	http://channeldv.com/public/mpg2compressed.JPG this TV screen snapshot was taken from DVD version. http://channeldv.com/public/uncompressed.JPG This was taken from a TV that was hooked directly to the A1 camera. So what is wrong with Canon A1 SD? When I hook up with this camera with HDV everything looks nice and smooth,....

November 4th, 2007, 11:16 AM	#7
Seun Osewa Major Player Join Date: Oct 2006 Location: West Africa Posts: 255	Near horizontal lines look like that on my camcorder too. I think it's a by-product of interlacing and in-camera sharpening. I wouldn't worry about it too much; there's nothing you can do. Normal interlaced TV programmes do have this artifact, but people dont even see such things unless they're looking for them.

November 4th, 2007, 01:59 PM	#8
Glenn Chan Inner Circle Join Date: Jun 2003 Location: Toronto, Canada Posts: 4,750	It could be that your TV introduces scaling artifacts.