Accession Number:

ADA114121

Title:

A Multi-Bit Rate Interframe Movement Compensated Multimode Coder for Video Conferencing

Descriptive Note:

Final rept.

Corporate Author:

BELL NORTHERN RESEARCH LTD OTTAWA (ONTARIO)

Personal Author(s):

Report Date:

1982-04-01

Pagination or Media Count:

92.0

Abstract:

This report describes a multi-bit rate video coder for DARPA video conferencing applications. The coder can operate at any preselected transmission bit rate ranging from 1.5 Mbs to 64 kbs. The proposed National Command Authority Teleconferencing System NCATS is designed to connect several conferencing sites. The system provides shared audio, video and graphic spaces. The video conferencing system communicates dynamic images of participants to different conferencing sites. The system is designed to operate under different bandwidth constraints. Under emergency situations communications bandwidth can be drastically reduced to allow only for 64 kbs to carry out the video conferencing system. Under normal conditions larger channel capacity is available for this service. In order to accommodate the above requirements, a video codec that can operate at different transmission bit rates is needed. This allows for upgrading of picture quality when there is sufficient bandwidth and a graceful reduction of picture quality under severe bandwidth limitations. The NTSC colour video signal sampled at 14.3 MHz 4 times the colour subcarrier frequency and uniformly quantized to 8 bits per picture element, requires a transmission bit rate of 114 Mbs. Such a high bit rate is economically prohibitive especially for video conferencing applications. In order to reduce the transmission bit rate, redundant information in the signal has to be removed and the specific video conferencing environment has to be exploited.

Subject Categories:

  • Non-Radio Communications

Distribution Statement:

APPROVED FOR PUBLIC RELEASE