Based on the research of videoconference systems of h . 323 protocol over ip networks and the author ' s experiences of implementing h . 323 videoconference systems in remote education area , in this thesis the main factors that affect videoconference quality are analyzed , and a dynamic bit rate allocation model is proposed and partly implemented . this model is designed to dynamically allocate bit rate for multi - media data flow ( including audio data and video data ) in fixed bandwidth network environment . when continuous multi - media packet losses are detected in ip based h . 323 videoconference system , the bit rate of video data is adjusted meanwhile the bit rate of audio data remains unchanged , and the bit rate allocation of multi - media data ( including audio data and video data ) is optimized as a whole effect 本文结合作者在h . 323视频会议系统应用于远程教育的经验，通过对现有的基于ip网络的h . 323协议视频会议系统的研究，分析了影响视频会议质量的原因，提出并部分实现了在固定带宽的网络环境下，基于ip的h . 323视频会议的多媒体数据包发生丢包、抖动或延时时，保持音频数据位速率不变，通过对视频数据的位速率的进行调整，最终实现旨在提高视频会议语音质量的多媒体数据位速率动态调整的模型。
Quadtree split is a simple but efficient method for organizing wavelet coefficients . we proposed a wavelet image coding method based on quadtree split , which exploits energy clustering in frequency and in space . using the fixed rate allocation method , we expand these two methods to 3d spatio - temporal subbands coding 四叉树分裂是一种简单有效的小波系数组织方式,本文考虑到视频序列时域高频帧非自然图像的特点,根据小波系数在频率和空间上的能量聚类特性,提出了一种基于四叉树分裂的小波图像编码方法。
