Research And Application On Digital Fountain Codes For Streaming Media Transmission

With the rapid development of Internet technology and the increasing Internet penetration, real-time streaming media applications, such as webcast, network video surveillance and video conference have obtained a great development. Streaming services mainly adopt UDP to transmit streaming media data, and the data is easy to be lost while transferred over the unreliable Internet channel. So it’s necessary to find a reliable way to transfer it.ARQ mechanism and forward erasure codes are two traditional ways to transmit data reliably. ARQ mechanism is not suitable for streaming media data transmission, because it may cause network congestion in multicast applications. The encoding process of traditional forward erasure codes has a high coding complexity, so it’s not suitable for real-time data transmission. Digital fountain code as a rate-less code, has a low encoding complexity and doesn’t need feedback channels. These advantages make it suitable for streaming media transmission. This paper is concerned with the application of digital fountain codes in streaming media transmission, and the main contents and results are as follows:1. This paper points out the drawbacks in streaming media transmission, and proposes a solution that applies digital fountain codes to channel encoding. By studying the encoding and decoding theories of LT and Raptor codes, it turns out that degree distribution is the key factor that influences the performance of digital fountain codes.2. This paper analyzes the delay problem in streaming media transmission and decides to focus on the digital fountain codes with short message length. It optimizes the robust soliton distribution and studies the optimal parameters. To improve the performance further more, this paper uses the stochastic characteristic of chaotic map during the encoding and decoding process.3. This paper designs a real-time streaming media transmission system based on digital fountain codes with small message length. It gives the detail design process of the data acquisition terminal and solves problems such as data declustering strategy, degree generator based on chaotic map, and duplicate adjacency problem. On the client side, a decoder based on BP decoding is proposed. On the server side, an optional encoding and decoding module is embedded to deal with the high-loss network. Based on the simulated transmission channel, the test indicates that the system designed in this paper has a good performance to reduce the packet loss.