It is well known that a block discrete cosine transform compressed image exhibits visually annoying blocking artifacts at low-bit-rate. A new post-processing deblocking algorithm in wavelet domain is proposed. The alg...It is well known that a block discrete cosine transform compressed image exhibits visually annoying blocking artifacts at low-bit-rate. A new post-processing deblocking algorithm in wavelet domain is proposed. The algorithm exploits blocking-artifact features shown in wavelet domain. The energy of blocking artifacts is concentrated into some lines to form annoying visual effects after wavelet transform. The aim of reducing blocking artifacts is to capture excessive energy on the block boundary effectively and reduce it below the visual scope. Adaptive operators for different subbands are computed based on the wavelet coefficients. The operators are made adaptive to different images and characteristics of blocking artifacts. Experimental results show that the proposed method can significantly improve the visual quality and also increase the peak signal-noise-ratio(PSNR) in the output image.展开更多
In the H.263 video codec related systems, motion estimation and Discrete Cosine Transform (DCT) have the most computational requirements. In order to reduce complexity of the encoder to dedicate more resources to othe...In the H.263 video codec related systems, motion estimation and Discrete Cosine Transform (DCT) have the most computational requirements. In order to reduce complexity of the encoder to dedicate more resources to other functions, according to the study of existing methods, an Improved All Zero Block Finding (IAZBF) method based on the statistic characteristics of DCT coefficients is proposed. Compared with existing methods, IAZBF improves the detecting efficiency by about 50% without importing too much extra computation requirement. Being computed with additions and shifts instead of complicated multiplications, IAZBF is of low computation complexity, especially for low-end processors. In addition, IAZBF upholds picture fidelity and remains compatible with the H.263 bitstream standard.展开更多
Due to coarse quantization, block-based discrete cosine transform(BDCT) compression methods usually suffer from visible blocking artifacts at the block boundaries. A novel efficient de-blocking method in DCT domain is...Due to coarse quantization, block-based discrete cosine transform(BDCT) compression methods usually suffer from visible blocking artifacts at the block boundaries. A novel efficient de-blocking method in DCT domain is proposed. A specific criterion for edge detection is given, one-dimensional DCT is applied on each row of the adjacent blocks and the shifted block in smooth region, and the transform coefficients of the shifted block are modified by weighting the average of three coefficients of the block. Mean square difference of slope criterion is used to judge the efficiency of the proposed algorithm. Simulation results show that the new method not only obtains satisfactory image quality, but also maintains high frequency information.展开更多
块离散余弦变换(B lock D iscrete Cosine Transform)的主要缺点是在低比特率时其恢复图像的块边界上会出现明显可见的方块效应,降低了图像的视觉质量.为了尽量消除块效应并保护图像的边缘信息提出了一种基于DCT域的块效应消除算法.该...块离散余弦变换(B lock D iscrete Cosine Transform)的主要缺点是在低比特率时其恢复图像的块边界上会出现明显可见的方块效应,降低了图像的视觉质量.为了尽量消除块效应并保护图像的边缘信息提出了一种基于DCT域的块效应消除算法.该算法充分利用了人类视觉系统(Hum an V isual System)特性,建立了块效应模型并给出一个简便的检测边缘标准,对于平滑区,对影响块效应的参数进行修正,然后用线性函数块代替阶跃函数块去除块效应,最后再对更新块和纹理区在DCT域中进行后滤波.仿真结果验证了本文算法的有效性.展开更多
基金Science and Technology Project of Guangdong Province(2006A10201003)2005 Startup Project of Jinan University(51205067)Soft Science Project of Guangdong Province(2006B70103011)
文摘It is well known that a block discrete cosine transform compressed image exhibits visually annoying blocking artifacts at low-bit-rate. A new post-processing deblocking algorithm in wavelet domain is proposed. The algorithm exploits blocking-artifact features shown in wavelet domain. The energy of blocking artifacts is concentrated into some lines to form annoying visual effects after wavelet transform. The aim of reducing blocking artifacts is to capture excessive energy on the block boundary effectively and reduce it below the visual scope. Adaptive operators for different subbands are computed based on the wavelet coefficients. The operators are made adaptive to different images and characteristics of blocking artifacts. Experimental results show that the proposed method can significantly improve the visual quality and also increase the peak signal-noise-ratio(PSNR) in the output image.
基金Supported by the China Aviation Fund (No. 02153071)
文摘In the H.263 video codec related systems, motion estimation and Discrete Cosine Transform (DCT) have the most computational requirements. In order to reduce complexity of the encoder to dedicate more resources to other functions, according to the study of existing methods, an Improved All Zero Block Finding (IAZBF) method based on the statistic characteristics of DCT coefficients is proposed. Compared with existing methods, IAZBF improves the detecting efficiency by about 50% without importing too much extra computation requirement. Being computed with additions and shifts instead of complicated multiplications, IAZBF is of low computation complexity, especially for low-end processors. In addition, IAZBF upholds picture fidelity and remains compatible with the H.263 bitstream standard.
基金Science and Technology Project of Guangdong Province(2006A10201003) 2005 Jinan University StartupProject(51205067) Soft Science Project of Guangdong Province(2006B70103011)
文摘Due to coarse quantization, block-based discrete cosine transform(BDCT) compression methods usually suffer from visible blocking artifacts at the block boundaries. A novel efficient de-blocking method in DCT domain is proposed. A specific criterion for edge detection is given, one-dimensional DCT is applied on each row of the adjacent blocks and the shifted block in smooth region, and the transform coefficients of the shifted block are modified by weighting the average of three coefficients of the block. Mean square difference of slope criterion is used to judge the efficiency of the proposed algorithm. Simulation results show that the new method not only obtains satisfactory image quality, but also maintains high frequency information.
文摘块离散余弦变换(B lock D iscrete Cosine Transform)的主要缺点是在低比特率时其恢复图像的块边界上会出现明显可见的方块效应,降低了图像的视觉质量.为了尽量消除块效应并保护图像的边缘信息提出了一种基于DCT域的块效应消除算法.该算法充分利用了人类视觉系统(Hum an V isual System)特性,建立了块效应模型并给出一个简便的检测边缘标准,对于平滑区,对影响块效应的参数进行修正,然后用线性函数块代替阶跃函数块去除块效应,最后再对更新块和纹理区在DCT域中进行后滤波.仿真结果验证了本文算法的有效性.
