Video image expansion method in ISDN communications system

摘要

The method involves using a pre-processor which decomposes a single input video image into spatial frequency sub-bands, whereby a low-frequency sub-band forms a video image which is smaller than the input image. A video encoder compresses the low-frequency sub-band into a first bit stream according to a desired standard. The high-frequency sub-bands are subjected to a pulse code modulation, and are transferred as a second bit stream over separate logical channels. Alternatively they may be transferred over the same channel as the first bit stream, but between single video images of the smaller image. A video decoder decodes the first bit stream in a receiver of the video system, and a PCM decoder decodes the high-frequency sub-bands. A post-processor combines low and high-frequency sub-bands for the reconstruction of a video image which comprises a larger format than used by the video encoder.