摘要:
描述了针对错误多发异质的网络环境进行视频编码系统总体设计的全过程。分析了外部需求,提出了改进视频表现、增强容错能力和提供可分级编码能力的系统设计目标。在简要介绍H.263+协议的全部16个可选的高级编码模式的基础上,重点分析了设计中对系统是否采用某个高级编码模式进行取舍的理由。对视频数据流的打包、错误掩蔽和错误跟踪的机制等方面进行了讨论。实际应用表明,根据本文设计进行的系统实现完全达到了原定的系统设计目标。
Abstract:
This paper describes the complete procedure of framework design on a video coding system for error-prone heterogenous network environment.First of all,the requirements of the system are analyzed and the targets of the system design are emphasized on three categories:①improving video performance under the constraints of network bandwidth and computational complexity,②providing error robust mechanism when packet loss occur,③adding capability of layered video coding for heterogenous network transmission.Then,ITU-T H.263+recommendation is introduced,especially about its 16 optional enhanced coding modes:feature,effect and benefit.The system design on mode selection is somewhat a trade-off.Five enhanced coding modes are preferred for our purpose:advanced INTRA coding mode,deblocking filter mode,modified quantization mode,slice structured mode and temporal,SNR and spatial scalability mode.At last,some useful and important system elements beyond H.263+recommendation are discussed:RTP packetization,error concealment and error tracking.Application shows that all the targets are easily touched by the implementation based on this design.
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