The improved display of 625-line television pictures: Adaptive interpolation

Some of the defects of a conventional 625-line television scanning system can be reduced, or even eliminated by signal processing in the receiver. The processing need not be very complicated, and most scanning system defects can be treated merely by raising the display scanning rate by standards conversion, or example to a sequential structure of 625-lines at 100 pictures per second, or an interlaced structure of 1250 lines at 100 fields per second. Although such structures do not suffer from the defects of the conventional 625-line system, other effects can arise if unsuitable conversion algorithms are used. Specifically, it is possible to define two algorithms, one best suited to the portrayal of motion, the other to vertical detail, and no compromise is suited to both. This Report describes an adaptive solution to the problem, involving varying the algorithm according to the output of a motion detector such that the appropriate algorithm was used for each pixel. The work was not completely successful in that the motion detector could not be adjusted to give completely acceptable results, although for non-critical test material the results were encouraging.