Abstract
We propose to use multiple-description coding (MDC) to protect video information against packet losses and delay, while also ensuring that it can be decoded using a standard decoder. Video data are encoded into a high-resolution stream using a standard compliant encoder. In addition, a low-resolution stream is generated by duplicating the relevant information (motion vectors, headers and some of the DCT coefficient) from the high-resolution stream while the remaining coefficients are set to zero. Both streams are independently decodable by a standard decoder. However, only in case of losses in the high resolution description, the corresponding information from the low resolution stream is decoded, else the received high resolution description is decoded. The main contribution of this paper is an optimization algorithm which, given the loss ratio, allocates bits to both descriptions and selects the right number of coefficients to duplicate in the low-resolution stream so as to minimize the expected distortion at the decoder end.
Highlights
In recent years, the volume of multimedia data transmitted over best-effort networks such as the Internet has continued to increase while packet losses and delays, due to congestion, routing delay, and network heterogeneity, continue to be commonplace
Most work in multiple-description coding (MDC) has been on balanced systems where each description is important, but we propose that for the low packet-loss rate conditions considered in this paper, a unbalanced MDC (UMDC) system would be more useful
The reported results are expressed in terms of the signalto-noise ratio (SNR) of the luminance components of the first 100 frames of the two QCIF (176 × 144 pixels) test sequences, namely, Akiyo and Coastguard
Summary
The volume of multimedia data transmitted over best-effort networks such as the Internet has continued to increase while packet losses and delays, due to congestion, routing delay, and network heterogeneity, continue to be commonplace. The main drawback of a predictive coding scheme is that even a single packet loss (or erasure) in the transmitted stream causes decoding errors to propagate through all the samples following the erasure. This severely affects the video quality available at the receiver and motivates the need for robust transmission of video data. Most work in MDC has been on balanced systems where each description is important, but we propose that for the low packet-loss rate conditions considered in this paper (below 10%), a UMDC system would be more useful.
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