ITU-TH.263源编码器可探讨编码模式的特点与分析

Analyses and Features of Negotiable Coding Options of H.263 Source Coder

ＩＴＵ－ＴＨ．２６３是用于甚低码率（＜６４ｋｂｉｔ／ｓ）下视频编码标准的一个建议草案。它是建立在ＩＴＵ－ＴＨ．２６１视频编码标准之上的。该草案包括了四种可探讨的编码模式以提高编码性能。高级预测模式可与无限制运动向量模式一起使用以提高预测性能及降低方块效应。ＰＢ－帧模式可在系统码率增加不多的情况下提高帧率。语义基算术编码模式用于替代变长编码，在重建图像及ＳＮＲ保持相同的情况下，可显著降低系统码率。本文中除了对这些模式的特点进行分析之外，还就其负面效应进行了讨论。

ITUT H.263 is a draft recommendation to be used as a very low bitrate (<64kbit/s) video coding standard,which is based on ITUT H.261 video coding standard.Four negotiable coding options are included in the recommendation for improved coding performance.Combined with Unrestricted Motion Vector mode advanced prediction mode can be used to improve the prediction performance and reduce the “blocking” effects.PBframe mode can increase the frame rate without increasing the system bitrate much.Syntaxbased Arithmetic Coding mode is used to take place of variable length coding.The reconstructed pictures and SNR will be the same,but significantly fewer bits will be produced.In addition to the analyses of the features of these modes,the paper discusses the side effects of them.