Adaptive Scan Method for Moving Picture Coding System

本文主要研究了以下三个方面的问题：（1）自适应加重滤波器提高编码运动图像质量及其硬件实现。（2）快门速度与抖动关系的研究。（3）视频编码中帧无关的帧间处理方法的研究在课题（1）中，我们提出了自适应的前滤波器和后滤波器。这些滤波器以较低的计算代价实现了编码噪声和超范围误差的降低。预滤波器根据图像的特点，突出高频分量。该预滤波器考虑蚊式噪声的出现区域，通过改变强调级别来降低蚊式噪声。后置滤波器根据前置滤波器的加重程度自适应地对高频分量进行去加重。最后，我们使用这些滤波器在DSP板上实现了一个实时编解码器。在主题（2）中，我们通过主观评价研究了抖动和拍摄参数之间的关系。在帧速率和物体运动速度相同的情况下，我们发现较高的快门速度和较高的亮度会增加抖动。我们还发现，较低的帧速率和较快的移动速度的对象增加抖动。从这些结果来看，抑制抖动的最佳设置等于帧速率中的快门速度。在主题（3）中，我们提出了帧无关的图像间编码方法。该方法对帧间差幅图像进行编码。该方法在解码后加入帧间图像，以减少解码误差。实验结果表明，PSNR提高了4dB，主观图像质量有明显优势。

We have researched three topics shown as follows,(1)Improvement of coded motion image quality with adaptive emphasis filters and its hardware implementation.(2)Investigation of relationship between shutter speed and judder.(3)Investigation of inter-picture processing method with frame independency for video coding.In the topic (1), we developed adaptive pre-filter and post-filter. These filters realize reduction of coding noise and over range error with low calculation costs. The pre-filter emphasizes high frequency component by adapting to picture characters. And this pre-filter includes mosquito noise reduction by changing emphasis level with considering appeared area of mosquito noise. The post-filter de-emphasizes high frequency components adaptively with relation to emphasis of pre-filter. Finally, we implemented a real-time codec on a DSP board using these filters.In the topic (2), we investigated the relations between judder and shooting parameters by subjective evaluation. In the condition of the same frame rate and moving speed of objects, we found that higher shutter speed and higher brightness increase judder. We also found that lower frame rate and faster moving speed of objects increase judder. From these results, an optimum setting for judder suppression is equal to shutter speed in frame rate.In the topic (3), we proposed inter-picture coding method with frame independency. This method encodes the picture of subtracted quantize error of inter-frames. After decodes, this method adds the inter-frame picture to reduce quantize error. Experimental results show 4dB PSNR improvement and significant advantage of subjective picture quality.