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Scaling filter effect

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Edmund Humenberger
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Scaling filter effect

Tue Jan 15, 2013 3:09 pm
I am very happy with KDEnlive (especially with the improved stabilty)

I just wanted to point out a filter which could use some improvement.

The scaling filter

http://www.youtube.com/watch?v=TvNtJZlqixY

Thank you

Yours
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ttguy
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Re: Scaling filter effect

Tue Jan 15, 2013 10:27 pm
Is this the scale and tilt filter? Have you tried pan and zoom. It might work better.

http://userbase.kde.org/Kdenlive/Manual/Effects/Crop_and_transform/Pan_and_Zoom
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ttguy
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Re: Scaling filter effect

Tue Jan 15, 2013 10:27 pm
Is this the scale and tilt filter? Have you tried pan and zoom. It might work better.

http://userbase.kde.org/Kdenlive/Manual/Effects/Crop_and_transform/Pan_and_Zoom
Edmund Humenberger
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Re: Scaling filter effect

Wed Jan 16, 2013 11:52 am
I use the "move and zoom" filter from Charles Yates

There is quite some jumping at the edge of the picture.
http://www.youtube.com/watch?v=K2kIMoWaZqU
especially on the right edge of the picture.

Small text is rendered badly when moving.
http://www.youtube.com/watch?v=3U2QoD0zyPk

markoc
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Re: Scaling filter effect

Wed Jan 16, 2013 2:42 pm
The problem you have is aliasing of the higher spatial frequencies in the picture. Sharp edges have high frequency content, and small text is hardly anything but high frequencies - so if you want to bring out aliasing problems, small text is what you need! To get perfect results on small text, you would need a sophisticated resampler, like Lanczos with a steep lowpass response - but that is very S-L-O-W, useful for single images, less so for video.

Luckily "natural" images tend to have much less high frequency components, so one can get away with simpler resampling algorithms.

If you can't avoid small text, maybe a slight blur before rescaling will help a bit.
der_pit
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Re: Scaling filter effect

Sun Jan 20, 2013 5:33 pm
There we meet again :D
I had the same trouble (see http://kdenlive.org/forum/pan-zoom-large-still-images), so using pan&zoom doesn't help. Also, there are quite some natural images that provide tons of high frequency: Tree leaves, grass etc.
Yes, a more sophisticated interpolator would be a great thing - even if it's slow.

For panning of images I now pre-scale the image to the desired dimension and then try to get the panning only do integer-steps. This obviously doesn't help for zoom...
markoc
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Re: Scaling filter effect

Sun Jan 20, 2013 8:39 pm
You can try different interpolators in the "corners" effect, should be possible to set the corners to get a pure zoom or pan.

I'm not sure for big zoom down ratios, as there is no additional pre-filtering in "corners".

P.S grass etc, being mostly random, is much less of a problem than small text, which is highly periodic, and produces strong beats.

normcross
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Re: Scaling filter effect

Mon Jan 21, 2013 6:54 pm
OK, Pan and Zoom with text on Kdenlive:-

http://youtu.be/jBduQdMcFGM

It's an image, twice with pan and zoom and text, 1080p
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ttguy
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Re: Scaling filter effect

Tue Jan 22, 2013 12:05 am
The text is not being pan/zoomed though.
normcross
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Re: Scaling filter effect

Tue Jan 22, 2013 12:22 pm
Ha, laugh, I never even noticed as I was watching the image move. Blind as a bat. I had another go with just the first clip though:-

http://youtu.be/xvaZ2LqA2Iw

EDIT:-

Last one, promise. Text moves across, up and gets larger:-

http://youtu.be/QZzJeMdzxLo


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