This paper designs a tree construction algorithm by distributing the layered steaming over the ALM in order to improve both the throughput and user delay. Firstly, by carrying out theory analysis, we define an out/in degree and the corresponding constraints to manage the layered streaming and nodes to improve the throughput. Besides, a novel method, called ALM-Bi-cast, is also proposed and analyzed to reduce user delay during the data-transmission. Secondly, by using the defined degrees and the ALM-Bi-cast, we present a tree construction algorithm and test it by simulations with NS-2. Simulations show that the proposal can get better results than other conventional methods. Finally, we carry out an implementation of our proposal, by distributing the video encoded by H.263+ over the ALM nodes placed in Tokyo City and Kyusyu Prefecture. Implementation further improves the out-performance of our proposal.

This paper presents the ITU-T Study Group 15 development of H-series Recommendations that allow interworking between different audiovisual communication terminals manufactured by different equipment providers. The paper focuses on H.310 and H.321 systems for broad-band ATM environments and H.322 and H.323 systems for LAN environments where the quality of service may or may not be guaranteed. The paper first lists the Recommendations developed by the ITU-T for audiovisual communication systems and the network environments in which they may be used. It then describes the design philosophy, the network specific characteristics, and hardware trials for each system. Then it describes the communication control protocol defined in H.245 which is used commonly by different audiovisual communication systems. Finally, the paper discusses interworking scenarios for communication between the different types of terminal on different networks.

This paper discusses a methodology for developing a new video coding standard through collaboration; use of the reference model. It is a coding model which may start from a simple framework, is used as a yardstick to evaluate new coding elements and/or improvements of existing elements and allows evolution by incorporating these new or improved elements whose effectiveness has been demonstrated into the next generation model. Then this new generation model serves as an updated yardstick for the next round of study. This process is iterated until a sufficient level of performance is obtained. An outstanding feature of this method is to enable decision making based on purely technical characteristics The work to develop ITU-T Recommendation H.261 is detailed in this paper as evidence of its productiveness by describing techniques employed as well as some potential techniques which were not accepted in the end. This method has also been verified by the subsequent successful development of MPEG-1 and MPEG-2 standards in ISO/IEC JTC1. Furthermore, it is pointed out that the reference model method also contributes to the efficient dissemination of the state of the art of the video coding technology. As a conclusion, some guidelines to apply this methodology are listed.>

A motion picture coding algorithm using motion-compensated interframe prediction and the adaptive discrete cosine transform (DCT) encoding technique is proposed. High coding efficiency is obtained by the adaptive DCT encoding technique in which encoding parameters are fitted to widely varying characteristics of the interframe differential signal. Segmented DCT subblocks of interframe prediction error are classified into categories based on their coefficient power distribution characteristics. The adaptation gain results from using a suitable variable word length code set designated by the above classification for encoding each quantization index of DCT coefficients. In addition, a new coding parameter control method is introduced based on the information rate estimation of the current frame. This classification promotes high stability because good estimation accuracy of bits consumption for each DCT subblock is obtained by utilizing the category indexes. Simulation results show that the proposed algorithm has enough coding efficiency to transmit videoconferencing motion pictures through a 384 kbit/s channel.

The experiment we conducted for integrated digital satellite communications is aimed at realizing integrated services digital networks by satellite communication. The experiment was carried out in 1980 using the Japanese experimental communication satellite "CS." This experiment uses 30/20 GHz small earth stations and demand-assignment time-division multiple-access (TDMA) systems. Communications between customer terminals, which contain video conferencing, high-speed facsimile communication, high-speed computer communication, and packet-switching signal transmission, were carried out through the experimental digital satellite link. This paper describes the configuration of the experimental integrated digital satellite communications system and the experimental results of communications between customer terminals.