On the implementation of software-only videoconferencing codec on PC

Intensive recent progress in computer technologies has stimulated new solutions for transmission of audio and video information in digital form, The transmission of digital video and audio signals through channels of restricted capacity, such as switched public telephone lines, mobile radio systems, local computer networks, Internet and satellite telecommunications attract a constantly growing interest. The bit rate in such lines available for transmission of audio and video information is limited dependent upon particular application in the range from 30 to 512 Kbit/s. In spite of the low bit rate digital coding itself requires significant computational resources and implies severe limitations on the performance of the real-time encoder. It should be also taken into account that for channels with low bit rate a codec must implement compression algorithms allowing us to achieve a large compression ratio and acceptable quality. Necessary compression ratios can be achieved only by means of intraframe coding as well as interframe motion compensation.