RATE-DISTORTION OPTIMIZATION IN A ROBUST VIDEO TRANSMISSION BASED ON UNBALANCED MULTIPLE DESCRIPTION CODING David Comas Teoria del Senyal i la Comunicació Universitat Politècnica de Catalunya Barcelona, Spain email:
[email protected]
Raghavendra Singh, Antonio Ortega Department of Electrical Engineering University of Southern California Los Angeles, California, USA email:{rasingh,ortega}@sipi.usc.edu
Abstract - We present an Unbalanced MDC video system where two bitstreams are generated, both independently decodable and compliant with the standard H.263 video decoder, and study the performance of the system in providing robustness in transmission over a packet network.
1. INTRODUCTION In recent years there has been an explosion in transmission of multimedia data over the Internet. With the current network not offering any guarantee on quality of service, packet losses and delays continue to be commonplace. This results in severe degradation in the decoded quality available at the end user if no protection is provided to the multimedia data. In particular if predictive compression schemes are used, even a single erasure in the bitstream can lead to catastrophic results due to the error propagation. These schemes are fairly common because they offer higher compression performance, e.g. DPCM for audio coding or Motion Compensation of video coding. The need for reliable transmission of a video or audio stream is immediately obvious. For delivering multimedia data through packet networks (e.g., Internet) local recovery of losses is often preferable to retransmission. Multiple Description Coding (MDC) is a forward error correction scheme where two or more descriptions of the source are sent to the receiver over different channels (Fig. 1). If only one channel is received, the signal can be reconstructed with distortion D1 (or D2). If both channels are received, information from the two channels is combined to achieve a lower distortion (D0
