Sunday, February 08, 2004

Virtual Dub Filtering

A lot of the stuff I'm currently working on came off of over-the-air broadcast TV, which means that it's not always the cleanest signal, especially if it was recorded onto a well-used video tape. So I'm experimenting a bit with VirtualDub filters to see how much the images can be cleaned up.

The "fill" filter is one that I definitely use if there is noise at the top/bottom of the frame (usually tracking errors). Basically, it covers up the junk with a flat black rectangle. This makes the encoder's job easier later on because it won't have to waste bits trying to encode a noisy margin. Setting up the filter properly is a bit backwards, if you want to get rid of noise at the bottom of a 720x480 frame, set the top Y box to 472 or 476. It helps if you initially set the color to a bright color and then check the output preview until you lock it in, especially if you're trying to do fills on all 4 sides of the screen.

The "smoother" filter seems to be another useful one. Even a setting of 5 or 10 along with the noise reduction pre-filter is enough to make the image look better, getting rid of some of the static or interference patterns in the signal. It should also make the compression codec more efficient when you go to encode later on. Downside is increase encoding time.

posted by Wuphon's at 10:25 PM