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Patterns and vertical lines – aliasing? XD HD 108050i

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Daniel De Avila
Patterns and vertical lines – aliasing? XD HD 108050i
on Aug 21, 2008 at 8:14:09 pm

Hello
I’m sure this topic has been posted before but my search skills are bit lacking.

Finishing up an edit, mostly interview/talking heads, and on my final outputs I’m getting some psychedelic waves /aliasing on anything that has a fine lines or patterns. For example, a shirt or a tie with vertical lines or thin lines.

On my output monitor all looks fine and my final render looks good too, all be it with some slight distortion. But scale it down to anything less than 720p and it really shows.

Perhaps this is a encoding problem but I when I looked carefully at the master footage I saw that there was a degree of wavy lines in the same places when scaled down, leaving me to think its apart of the source footage and its getting amplified as I scale down to lower resolutions. I also see this if I encode the master footage to any lower resolution.

Don’t really know what am asking here. It would be nice is someone could post back and say “what you need to do is...” But I would be just as happy to see if anyone has an explanation for this, what Im doing wrong, and any suggestions on how to avoid it in the future.

Some tach info:
Source footage: XD HD 108050i 35 (35 Mb/s VBR). Used XD Cam transfer tool to import the footage.

Edited in a XDCAM EX 720p25 sequence and source footage de-interlaced with Nattness plug in.

Tried the Anti-alias and the flicker filter but still getting less desirable results.

Sincerely
Daniel



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Tom David
Re: Patterns and vertical lines – aliasing? XD HD 108050i
on Aug 22, 2008 at 2:53:18 pm

Think I know what you're getting at with your description, and first of all I would say use the anti-flicker filters.

I don't think you would need de-interlacing filter to edit 1080i on 720P sequence - the de-interlacing should happen automatically if I am correct, as 720P sequence is progressive anyway.

Try nesting your whole edit, and drop it onto a 720P sequence - THEN apply the flicker-free filters.

Otherwise, failing that, unless you're editing on a Blackmagic or AJA video card, there have been lots of people trying to overcome down-converting problems of from HD footage into SD with this XDCam format - and the lines you have described are part of that problem. Ultimately, its best to shoot 720P if you plan to shoot on a 720P timeline, which I believe the EX1 can shoot anyway. Good luck!


Cheers,
Tom

Camera Operator - Editor - Motion Graphics
(http://www.tomdavid.com.au)


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Daniel De Avila
Re: Patterns and vertical lines – aliasing? XD HD 108050i
on Aug 22, 2008 at 5:10:12 pm

Many Thanks for the suggestion Tom.

It’s a bit late now in my end of the world and Im off home. But Ill be able to try your suggestions this Tuesday and post back.
Sincerely
Daniel





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