High definition television coding arrangement with graceful degradation

Abstract

Graceful degradation for digitally encoded HDTV signals is achieved by appropriately coding the image to provide a controllable degradation of chosen image characteristics, such as temporal degradation, spatial degradation, and dynamic range degradation. In the temporal degradation approach of this invention, the resolution of movement suffers when noise is introduced. In the spatial degradation approach, the spatial resolution of the image is sacrificed. In the range degradation approach, the dynamic range of the signals is sacrificed. The graceful degradation is achieved by dividing the transmitted signal into two or more parts, such as parts A, B and C. Part A is given the heaviest error-correcting code; part B is given a 'medium' error correcting code; and part C the is given the least powerful error correcting code (or perhaps none at all). A receiver that is close to the transmitter most likely receives parts A, B and C. A receiver that is farther away gets a noisier signal might and, perhaps, correctly receive only parts A and B. A receiver that is at the limits of the transmitter range might receive correctly only part A. Of course, the signals of parts A, B and C are constructed in a hierarchical fashion so that part A provides basic signal information; part B augments the basic information to produce a better picture; and part C augments part A plus B to produce the highest resolution picture.