A compatible coding system for 1125-line, 60-Hz HDTV and 525-line, 60-Hz standard TV is presented. This system allows an HDTV signal to be transmitted at about 140 Mb/s. From the coded HDTV signal, a standard TV signal as well as the HDTV signal can be easily decoded. The coding algorithm uses adaptive intrafield/interframe discrete cosine transform (DCT) coding in which only low-frequency components of the coded DCT coefficients are used for the reconstruction of the standard TV, while all frequency components are used for HDTV. The configuration of a compatible codec is based on this scheme. The architecture uses parallel DCT coding to realize signal processing at very high sampling rates. Computer simulation results show good picture quality for both decoded HDTV and standard TV.<>