Visual telephony as an ISDN application

The key factors deterring the use of visual telephony are identified, and an overview of a typical system architecture is given. The video signal formats and video and audio coding algorithms used are described. Video codec implementation is considered, and an implementation based on application-specific integrated circuits is presented. In particular, three key signal processing modules in the video codec are examined: a discrete cosine transform chip, a motion estimation chip, and a variable-length codec chip. Standardization activities in the video coding area are discussed.<>