Multiple description coding

Abstract: A secondary packetized data stream, such as a commercial, is spliced with a primary packetized data stream, such as a network television program. The system does not require decompression of the data in the primary data stream, and is particularly suitable for use at a cable system headend to allow the insertion of commercials from local businesses into a nationally broadcast television program. When a start signal is received, a pre-splicing packet of the primary stream is determined. The pre-splicing packet is the packet closest to the start time which carries an anchor frame (e.g., I or P frame) start code. To prevent a potential discontinuity at the decoder, the pre-splicing packet is processed to discard the anchor frame data, and to insert a number of stuffing bytes which is equal to the number of bytes discarded into an adaptation field of the pre-splicing packet. To further maintain continuity at the decoder, identifying data of the primary stream such as PID and PSI data, is retrieved and provided to the secondary stream. A number of null packets are inserted into the output stream at the transition point between the main program and the commercial to prevent a buffer overflow at a decoder which receives the output stream.

Abstract: Recently, multiple description source coding has emerged as an attractive framework for robust multimedia transmission over packet erasure channels. In this paper, we mathematically analyze the performance of n-channel symmetric FEC-based multiple description coding for a progressive mode of transmission over orthogonal frequency division multiplexing (OFDM) networks in a frequency-selective slowly-varying Rayleigh faded environment. We derive the expressions for the bounds of the throughput and distortion performance of the system in an explicit closed form, whereas the exact performance is given by an expression in the form of a single integration. Based on this analysis, the performance of the system can be numerically evaluated. Our results show that at high SNR, the multiple description encoder does not need to fine-tune the optimization parameters of the system due to the correlated nature of the subcarriers. It is also shown that, despite the bursty nature of the errors in a slow fading environment, FEC-based multiple description coding without temporal coding provides a greater advantage for smaller description sizes.

Abstract: We consider the problem of distributing "live" streaming media content to a potentially large and highly dynamic population of hosts. Peer-to-peer content distribution is attractive in this setting because the bandwidth available to serve content scales with demand. A key challenge, however, is making content distribution robust to peer transience. Our approach to providing robustness is to introduce redundance; both in network paths and in data. We use multiple, diverse distribution trees to provide redundancy in network paths and multiple description coding (MDC) to provide redundancy in data. We present a simple tree management algorithm that provides the necessary path diversity and describe an adaptation framework for MDC based on scalable receiver feedback. We evaluate these using MDC applied to real video data coupled with real usage traces from a major news site that experienced a large flash crowd for live streaming content. Our results show very significant benefits in using multiple distribution trees and MDC, with a 22 dB improvement in PSNR in some cases.