This provides a two-dimensional low pass filter function in order to generate a lower resolution rendition of the image. The lower resolution image is then decimated to reduce its size to half that of the original in both the horizontal and vertical direction. The filtering process is repeated recursively to generate a total of three images of progressively lower resolution and smaller size. An identical spatial process is used to interpolate the lowest resolution base image to the next larger image size and subtract it from the image existing at this size to provide the mid-band detail. The detail bands are quantized and entropy encoded in a data compression unit.
Error correction is appended to form the final compressed video digital data stream.
The decoder uses the same chip set as the encoder. The lowest bands are scan converted to the next higher scan resolution, post-filtered and added to that band. This process is continued until the full resolution image is generated. Since this process is the inverse of the encoding process the reconstruction is exact except for the gray scale and temporal information that is left out in the higher bands. The compression that results from the entropy codes is also lossless.