Abstract: An encoding scheme resistant to transmission errors encodes a data bitstream for application to a quadrature amplitude modulator (QAM) in a high definition television system. The error-resistant code provides a rotationally symmetrical 32-point constellation on a plane defined by I,Q quadrature axes. The constellation is divided into first and second partitions arranged so that constellation points that are closest in distance to any constellation point of the first partition belong to the second partition, and constellation points that are closest in distance to any constellation point of the second partition belong to the first partition. The binary value of one bit of each of successive 9-bit packets in the bitstream determines that one of the two partitions to which both of a consecutive pair of first and second constellation-point transmissions belong (the first and second transmitted constellation-points of that consecutive pair being selected by the then current 9-bit packet of the stream).

Abstract: A video signal generating system develops an encoded video signal representing less than all of the video information. Auxiliary signal generating circuitry develops a pair of auxiliary signals representing in part the remaining video information. A first of the pair of auxiliary signals includes relatively high fidelity signal but with limited bandwidth. The second auxiliary signal includes relatively low fidelity information but has an effective higher bandwidth. Depending upon the information density of the auxiliary information, the first and second auxiliary signals are selected to produce an auxiliary output signal which is combined with the encoded video signal for transmission. A receiver responsive to the transmitted signal separates the video and auxiliary signals. The video and auxiliary signals are decoded and used to generate enhanced display images.