Suboptimal Quantization Control with Estimation of Rate- Distortion Relationship for Motion Video Coding

• Main Authors: Chien, Yu-Ming, 簡裕民
• Other Authors: David W. Lin
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/34784852886020596267

碩士 === 國立交通大學 === 電子研究所 === 84 === For image and video coding under transmission constraints, determination of quantization steps at encoder plays an important role in controlling the generated bit-rate and coding performance. In this thesis, we analyze the quantization information from some Video CD titles and compare them with several known rate control algorithms. In addition, we investigate how to determine quantization steps for good coding quality. We approach this by improving on a well-known quantizer control algorithm, namely, Test Model of MPEG2. We know that the rate-distortion curve of a macroblock fully characterize the relationship between rate and distortion and can thus be used in determination of good quantization steps. Becasue of the heavy computational load required for calculating the real R-D curves, we develop a piecewise approximation model to predict the real curves. In deciding an appropriate quantization step, we first calculate a reference step on the buffer status to prevent the buffer from overflow and underflow. Next, the human vision factor and the slope of the estimated rate-distortion curve are incorporated into adjustment of this quantization step to obtain a suboptimal quantization step. Simulation reesults show that, we can attain not only higher PSNR values but also higher human visual quality in coded video.