Adaptive Scan Method for Moving Picture Coding System

本文主要研究了以下三个方面的内容：(1)利用自适应加重滤波器改善运动图像的编码质量及其硬件实现。(2)研究快门速度与抖动的关系。(3)研究视频编码中帧无关的图像间处理方法。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。预滤器通过适应图片字符来突出高频成分。该预滤波包含了根据蚊子噪声出现的面积改变侧重点的方法来降低蚊子噪声。根据预滤波的重点，后滤波自适应地去强调高频分量。在主题(2)中，我们通过主观评价来研究抖动与拍摄参数之间的关系。在相同帧速率和物体移动速度的情况下，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对象移动速度会增加抖动。根据这些结果，抖动抑制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。该方法对帧间量化误差相减后的图像进行编码。该方法在解码后加入帧间图片，以减小量化误差。实验结果表明，4dBPSNR提高，主观画质有明显优势。

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.