Abstract: A temporally-subsampled video signal from a bandwidth reduction encoder is processed prior to transmission in order to reduce the judder effects that would otherwise be present when the encoded signal was viewed directly on a receiver not equipped with a bandwidth reduction decoder. A fraction 1/N of the samples are transmitted in the first field of each group of N fields, where N is the temporal subsampling ratio. Each of the other N-1 fields is formed by projecting the first field along the estimated motion trajectory to the appropriate time instant and adding to this projection the difference between another group of the N/1 samples and an estimate of these samples derived from those transmitted in the first field. At the decoder, the projected fields and the estimate of the samples can be derived from the samples in the first transmitted field of the group for each subsequent field.

Abstract: A correlation surface is derived by phase correlating two pictures selectively displaced in the X and Y directions. The illustrative surface shows a large peak at zero displacement, corresponding to a stationary background, and a fairly large peak corresponding to a moving object, the X, Y position of the peak indicating the magnitude (pixels per field period) and direction of the motion vector. A set of motion vectors is thus determined and testing is then carried out, on a pixel by pixel basis or pixel block by pixel block basis, to determine which of the motion vectors gives the best match in deriving the second picture from the first. The motion vector thus assigned may be used in temporal interpolation of the pictures.

Abstract: At the transmitter a coder includes a motion vector generator providing vectors (MV) describing the movement of individual blocks of pixels. The video signal is 4:1 compressed in bandwidth by pre-filters and a sub-sampling unit to produce a signal (SSH) from which a high-definition image can be re-constructed in the coder and in the decoder. The sampling lattice is shifted in accordance with the motion vectors (MV) which are digitally transmitted along with the compressed bandwidth analogue signal, to enable the samples to be correctly located in the reconstructed image. Poorly correlated moving areas are handled by pure spatial filtering (pre-filter and sub-sampling unit) with reconstruction by spatial interpolation. The two reconstructed signals (RVH and RVL) at the coder are compared in a mode selector with the input video and a switch is set to transmit whichever of the compressed signals (SSH, SSL) gives the best match.