Adaptive Scan Method for Moving Picture Coding System

本文主要研究了以下三个方面：(1)利用自适应重点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)基于帧无关的视频编码图像间处理方法研究。在课题(1)中，我们开发了自适应预滤波器和后滤波器。这些滤波器以较低的计算成本降低了编码噪声和超距误差。预滤波器通过适应图像特征，突出高频分量。该预滤波器考虑蚊虫噪声的出现面积，通过改变重点级别来降低蚊虫噪声。后滤波器相对于前滤波器的重点自适应地去强调高频分量。最后，我们利用这些滤波器在DSP板上实现了一个实时编解码器。在课题(2)中，我们通过主观评价的方法研究了抖动与拍摄参数之间的关系。在相同帧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，较低的帧率和较快的物体移动速度会增加抖动。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。在课题(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像，减小量化误差。实验结果表明，改进后的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.