Tools for Image and Video Transmission over Heterogeneous Network

目前大多数数字视频系统仅仅是用更高效的数字视频传输方式取代现有的模拟视频传输模式。然而，随着基于分组的网络，如因特网，开始成为通信基础设施的重要组成部分，通用计算机成为主要的通信终端，需要提供一套新的视频压缩和处理算法，这些算法针对端到端软件处理环境进行了优化。接下来的挑战是找到有效的方法将视频数据嵌入到基本的异步传输/处理基础设施中。为了应对这一挑战，该项目集中在两个主要领域：(i)计算/带宽可扩展编码和（ii）健壮的异步视频传输算法。Internet是一个异构网络，就其组件（主机、路由器）以及可用带宽和处理速度而言都是如此。因此，带宽/计算可伸缩的算法是理想的，以降低视频质量为代价实现较不复杂的编码/解码。该项目正在开发一种针对可变复杂性、输入依赖编码/解码算法的设计方法，其目标是优化平均（而不是“最坏情况”）复杂性性能，同时也在开发健壮的异步视频传输算法，因为互联网提供的传输可靠性有限。视频不仅对信息丢失敏感（例如，由于拥塞导致的数据包丢失），而且对过度延迟也很敏感。这项工作集中于异步视频传输的新压缩技术，其中每个视频单元（帧的一部分）都有一个“生命周期”，在此期间它是有用的，并且可以跨越多个单一帧时间间隔。该领域包括速率控制和图像域纠错/检测技术方面的新工作。

Most current digital video systems merely replace existing modes of analog video delivery with their more efficient digital counterparts. However, as packet-based networks, such as the Internet, start to be an essential component of the communications infrastructure and general purpose computers become the predominant communication terminal, there is a need to provide a new set of algorithms for video compression and processing, which are optimized for an endto- end software processing environment. The challenge is then to find efficient ways of embedding video data on a fundamentally asynchronous transmission/processing infrastructure. To address this challenge this project concentrates on two main areas: (i) computation/bandwidth scalable coding and (ii) robust asynchronous video transmission algorithms. The Internet is a heterogeneous network, both in terms of its components (hosts, routers) and in terms of available bandwidth and processing speed. Thus bandwidth/computation scalable algorithms are desirable to enable less complex encoding/decoding at the expense of a reduction in video quality. This project is developing a design methodology for variable complexity, input dependent coding/decoding algorithms where the goal is optimizing average (instead of "worst-case") complexity performance, robust asynchronous video transmission algorithms are also being developed, as motivated by the limited transmission reliability offered by the Internet. Video is sensitive not only to losses of information (e.g. packets being dropped due to congestion) but also to excessive delay. This work concentrates on new compression techniques for asynchronous video transmission where each video unit (a part of a frame) has a ``lifetime'' during which it is useful, and which can span more than a single frame time interval. This area includes novel work in both rate control and image domain error correction/detection techniques.