Optimized hybrid transform coding for very low bit rates: videotelephony communication on personal computer
Gérard Eude, Jean‐Claude Schmitt · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1994
This paper describes a `very low bitrate visual telephony application' demonstrator which was designed to be used on the Public Switched Telephony Network for many multimedia purposes. This development was done by CNET in coordination with the european COST211ter project with the aim to demonstrate videotelephony at very low bit rates. The main concern was to optimize a video coding algorithm based on the CCITT H.2161 existing standard and directly derived from the COST211ter simulation model. The different signals which are needed for a videotelephony communication, video, speech, data and control are modulated and transmitted at a bitrate contained between 9.6 kbit/s and 28.8 kbit/s. The description of the demonstrator is given, including video algorithm and system multiplex specifications. The reasons of the choice of the video format and algorithm are also discussed. A friendly software application has been developed to run videotelephony within a Macintosh computer environment. This program uses the QuickTime routines to record and to play the videophone pictures to or from the hard disk. Single pictures or large sequences can be grabbed to the hard disk. Data can also be transmitted by opening, through the audio/video multiplex a data channel of some kbit/s in the video channel, allowing minimal groupwave application.