Image Processing Reference
solution but is usually too expensive or impractical. Installing some mains filters might
solve the problem more cheaply.
Because this is electrical noise from the same mains supply that the TV picture was
displayed on, it is likely that the noise will be synchronous with the frame rate and there-
fore more or less stationary on the screen. If you are lucky, it will be located near the top
or bottom and might be removed with a crop.
Figure 36-10 Washing machine noise.
1. Turn off the offending appliance.
2. Install a mains filter.
3. Apply a dropout compensator.
4. Crop if possible.
Living near an airport may result in some interference from the ground-approach radar.
This noise is very distinctive. If the atmospheric conditions are right, you may suffer from
this even if you live a long distance away.
The noise pattern (Figure 36-11) is distinctive because it's a set of well-defined pulses
that cause quite lengthy dropouts in the signal. The cyclic nature may help you to set up
a filter, but it is rare for the cycle to be in sync with the video, so the effect will roll through
Figure 36-11 Radar noise.