Antiflicker
Filter for Virtual Dub - Version 2.0
[ Prepare phase ]
(c) Alessandro Malanca - Jun / 2002
http://web.tiscali.it/minomala/index.html
[Place this text file in the
VirtualDub plugins directory.]
When video at one frame rate is projected and then
recorded from the projection screen at a different frame rate, a temporal moire
pattern, or flicker, is produced. This filter removes the flicker, thereby
making this a viable process. For example, it becomes feasible to project 18
fps films and record them with a 25 fps PAL camcorder.
The filtering is realised using two different filters: DeflPrep
e DeflProc.
The first filter DeflPrep is used to pr process the video
and saves its work in a given file. The second DeflProc, opens the file
prepared by DeflPrep and apply the corrections to the video.
Preparing
Phase
Here is the step-by-step process.
1. Start
VirtualDub.
2. Open
the input video.
3. Add
the DeflPrep filter. Set interlacing if your source video is interlaced
optionally set the "Save as..." file and save the filter with OK, OK.
4. Now
on the VirtualDub timeline, play the video through to completion using the
>o button. The output pane will show the frame processing progression. Do
not rewind or anything else yet! (You
may NOT move around on the timeline in "Prepare video" mode. If you
rewind, you have to play through again until completion.)
5. select
filter and delete DeflPrep.
6. You
can now add DeflProc filkter and go to processing phase.
The following options are available in the Prepare
filter:
Interlaced source:
If the source video clip
is interlaced, check this option to enable field-mode processing. It will be
saved in the file, to be further used in the processing phase.
Save as... :
you can specify the path
to the file used to store the original luminance values and some parameters.
Technical notes.
The first phase of the filter simply save an indicator of
the global luminance for each frame or field (for interlaced video). The second
phase of the filter performs a moving average over the video and rescales the
pixels in the frames to approach this average. It applies a temporal softening
too.
Thanks to Me, Donald Graft and Niels Basjes for
suggesting the creation of this filter, providing test files, and giving
valuable feedback. The final temporal softening phase is adapted from code by
Steven Don. Thanks to Jeff Gonion for valuable theoretical discussions on
digital filtering.
This version has been reworked by :
Alessandro
Malanca, June 19, 2002
(C) Copyright 2002-2004, All Rights
Reserved
http://web.tiscali.it/minomala/index.htm
Filters for VirtualDub
Donald Graft, March 30, 2002
(C) Copyright 2000-2002, All Rights
Reserved
http://sauron.mordor.net/dgraft/index.html