The authors are currently the faculty in Department of Electronics and Communication, Pondicherry Engineering college ,pondicherry, India. 1 OPTIMAL CODING AND RESOURCE UTILIZATION FOR REAL-TIME MPEG OVER ATM NETWORK K.Jayanthi, G.Sivaradje, and P.Dananjayan Department of Electronics and Communication Engineering Pondicherry Engineering College, Pondicherry, India. Email: shivaradje@ieee.org Abstract In this paper, a scheme to enhance the image quality and utilize the network resources optimally is proposed. The gain is achieved by statistical multiplexing in VBR transmission but the network quality is variable since buffer controlled and network enforcement is both inactivated. Hence, enforced VBR transmission is employed in the proposed method. The objective is achieved by developing an optimum coder model in which enforcement and buffer control is done to maintain subjective image quality, constant and avoid buffer underflow and overflow. In addition, the optimum resource utilization is achieved by developing a dynamic bandwidth allocation algorithm in which the available bandwidth is redistributed among the various uses at each node in the ATM network. 1. INTRODUCTION One of the most important issues in ATM traffic control is to maximize the utilization of network resources while satisfying the quality of service (QoS) requirements. Variable bit rate video is currently one of the most challenging real time applications for asynchronous transfer mode networks. A key benefit of ATM technology is its ability to provide QoS guarantees to applications. Several classes of service have been defined in the context of ATM networks to satisfy the QoS needs of various applications. The Constant Bit Rate (CBR) and Real-Time VBR (RT- VBR) services are intended for real time application that require low delay and jitter. VBR transmission of video over ATM networks provided substantial benefits both in terms of network utilization and video quality. In general, for real time transmission like video and voice over ATM network, CBR and RT_VBR (Real Time VBR) are used. In CBR the end-to-end image, quality is maintained constant but the network resources are not used optimally, the gain obtained by statistical multiplexing is not used due to PCR used in CBR.RT_VBR though the network resources are used optimally, the image quality is not that good as in CBR. To overcome this problem in CBR and RT_VBR enforced VBR transmission to maintain both image quality and optimum utilization of network resources is proposed. To reduce bandwidth needed video is usually compressed before transmission. The Motion Pictures Experts Group(MPEG) coding scheme has developed as a standard of video compression. Since video has been highly compressed, cell loss during transmission of MPEG-coded video may cause serious degradation of image quality. Low cell-loss-rate network operation or schemes that facilitate such operation are therefore essential. At present, the ATM networks are providing the Constant Bit Rate (CBR) services and assigns the peak rate bandwidth to all the real time applications than to say to all VBR applications. In CBR service, a fixed value of bandwidth is allocated for each connection. Because of the variable bandwidth requirement there is potential waste with peak-rate bandwidth assignment. To improve the performance of the of ATM networks an accurate estimate of the amount of resources that the VBR traffic must reserve becomes a very important issue. The proposed method presents an approach to dynamically allocate the bandwidth for the transport of the real-time MPEG videos in ATM networks. The method would increase the bandwidth utilization by assigning the spare bandwidth in the network, to the frames whose bandwidth requirement exceeds the allocated value. Further the usage of traffic smoothing techniques like buffering may still increase the performance. 2.VIDEO TRANSMISSION OVER ATM NETWORK The video transmission over ATM network is one of the challenges because it involves large bandwidth requirement, almost no timing delay, and a very high speed of transmission. The uncompressed video needs enormous bandwidth and it is very bursty in nature. Transmission of uncompressed video over ATM Network lowers the Network utilization. Hence, the video stream is first compressed using MPEG. MPEG video compression algorithm is the most efficient one because it is capable of providing different qualities depending on the bit rate from TV Broadcast to studio quality [1,2].