This paper describes a software-based H.264/AVC HDTV real-time interactive CODEC architecture (named RISCA264-HD) using parallel processing. The RISCA264-HD consists of multiple high-speed encoder/decoder cores, an IP communication part, and an error recovery controller with FEC. It provides Full-HD quality (1920 x 1080 pixels, 29.97 frames per second) using parallel encoding, natural interactive conversation with low delay of less than 165 ms, and smooth visual communication free from macro block noises. This software with a home television and a home digital video camera achieves HDTV-quality bidirectional video communication via commercially IP broadband network.