My first VirtualDub filter!

DESCRIPTION
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It is designed to allow you to "smear" the regions at the top and bottom of a frame.

This might be a useful option if you are capturing video for use in say a fixed VCD format.  If you crop your video to get rid of rubbish (say from VHS capture) you normally have to add a solid border or resize to get the clip to the right dimensions for you MPEG encoder (I'm a TMPGEnc person myself).

I've heard from others that MPEG coders don't like solid borders because although they compress OK, the transistion between the picture and the border often causes noticable artifacts (unless the borders are a multiple of 16pixels).

Resizing can cause problems, especially if the material is interlaced.

INSTRUCTIONS
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The best way to use the filter is by slow experimentation, since what is nice depends very much on the source material and your objectives.  These instructions apply equally to the top and bottom of the clip being processed but I'll just refer to the top from now on for simplicity.

The Black Border Region should hopefully be obvious - it just creates a solid border.  As above, set it to multiples of whatever your codec is happy with (e.g. 16 for MPEG/VCD) (please send me any info on other codecs).

To start smearing, increase the Smear Region value until you notice some smearing and then stop!  Sometimes, if your source edge isn't well defined you might be better off increasing the value by a few lines.

So far, the filter has been non-destructive (we've only smeared a region that didn't contain any useful info), but the effect might be considered a bit too simple - time for a bit of tweaking.

The filter at this point is just duplicating the topmost line of "real" video.  You can now apply a stretch factor or a fade.

The Fade Region value will progressivly fade up from whatever line is set by this value to the Border Region line value.  This can disguise the simple smear a bit and can be used independantly for its own simple effect.

The Stretch Factor modifies the simple smear by using multiple lines of video instead of just one line.  It can give a much more pleasing visual effect at the expense of distorting lines of video containing "real" picture information.

The stretch facility doesn't work very well with interlaced material at present - in the interim I suggest using Smart DeInterlacer by Donald Graft or Area DeInterlacer by Gunnar Thallin prior to this filter if the material is interlaced.

Any comments or suggestions for improvements (not involving a PhD in image manipulation) would be greatly welcomed.

Simon Walters
siwalters@hotmail.com

VERSION HISTORY
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V1.0 24th October 2000

Added ability to stretch the top and bottom instead of just smearing.  (This was my objective when I started the filter :-)


V0.4 - 23rd OCtober 2000

The filter now allows you to set a solid black border (if anyone wants colour - email me).  This should be set in increments of 16 if final compression is MPEG for VCD.  Other methods are happy with 8,4 or 2 (but I don't know which).

You can now set the fade to black region separatley from the smear region (I find a couple more lines that smear is about best myself).

Both the smear and fade regions stop at the border region.


V0.3 - 10th October 2000

Added a better blur alogrithim.  If you set Blur option to 1 the filter will do a fade to black as well as smearing.

