VirtualDub Plugins

(Yeah, there's only one right now.)


Download filter with source code

README file:
"NoDrops" video filter for VirtualDub

v0.1  (3 Oct 2005)
by Charles Boling

Source code adapted from the tutorial included with the VirtualDub SDK.
Do whatever you want with it.


This filter was created to get rid of the annoying solid lavender fields put out
by my Osprey 100 video capture card when capturing video from some
worn-out VHS video tapes.  They apparently represent fields it dropped because
it couldn't get a clean signal.

Most often, one field of a frame will be dropped, while the other is okay.
In fact, many times that one field will be dropped for several frames (i.e. it's
catching every other field).  Sometimes an entire frame will be dropped, or even
several consecutive frames.

The filter works with both interlaced and non-interlaced sources, though it was
designed specifically for interlaced.


Note: "Blank" refers to a dropped frame that matches the specific lavender color.

It scans each row in a frame to see if it's "blank"or not.  If not, it keeps it
unchanged.  If it's blank, it attempts to reconstruct an approximation of the
original frame in one of two ways:  temporal duplication or spacial duplication.

If the corresponding row in the previous frame is okay, it will copy it.  If the
row in the previous frame is blank too, it will instead grab the previous row
of the current frame (or next row, if we're looking at the 1st row) and use it.


When the preferred temporal duplication is used, the "comb effect" is increased
in moving parts of interlaced frames where a single field is missing, but the
increased resultion is maintained in the non-moving parts.

In non-interlaced video, or in interlaced frames with both fields missing, this
will show up as jumpiness, since the entire frame is copied, rather than every
other row.

When Spacial Duplication, or "scan line doubling" is used in an interlaced video
stream, a temporary loss of vertical resolution occurs over the entire frame.

If an more than one entire frames are missing in a sequence, only the first one
will be repaired (unless half the previous one was dropped too, in which it will
only have half the scan lines repaired), but the rest of the frames in the
sequence will still be blanked out.

It's not perfect, but it's a vast improvement over the constant "pink flashes".


This filter was created to fulfill a pretty specific need for myself.
Things I can think of to improve, but haven't because of a lack of time, as well
as not really knowing much about either C programming or video filters:

1. Add MMX Optimizations
2. Allow user to change "dropped" color (maybe not needed.  I don't know if
   other video cards do a similar thing or not, or if a different setting on
   the Osprey would change the output color.)
3. Interpolate rather than duplicate.  Lots of interpolating filters out there
   to copy; perhaps no need to reinvent the wheel.
4. decide on each frame (or row, or piece of a row) whether temporal or spacial
   interpolation would be more accurate; maybe use both when available to
   produce a more accurate estimation.

Comments?  Send email to: vdub <at>