INTERPOLATING FINER INTENSITY LEVELS IN DITHER-QUANTIZED TELEVISION PICTURES

A receiver interpolates finer intensity levels in critical areas of a dither-quantized TV picture that is sent (or recorded) with very few intensity levels. This improves picture rendition and reduces the visibility of stipple dots. One embodiment, for video quantized with multiphase ordered dither, substitutes the mean of several successive frames at all picture elements that are not changing with time. Another embodiment averages spatially on the frame in areas devoid of high-resolution detail. Both versions use a simple test for activity that permits instant pel-to-pel switching between averaged samples and input samples. The two embodiments can be combined.