Method for preprocessing noise reduction and block effect removal in low bit-rate video application

Abstract

The invention discloses a method for preprocessing noise reduction and block effect removal in low bit-rate video application. The method comprises the following steps: analyzing gradient by matrix eigenvalue; carrying out edge detection by a gradient analysis module; carrying out corrosion operation on a gradient map corresponding to an initial image to eliminate a gradient point generated by single noise; carrying out expansive operation to connect edges corresponding to the gradient point; performing motion detection by adopting a motion detection module to evaluate the motion area of the image; and selecting a two-sided filter with proper strength for filtration by adopting a filter strength determine module according to the code rate, gradient and motion characteristic. Two parameters of the two-sided filter are grey difference information and distance information. The method not only reduces noise, filters unimportant details for high efficient compression, avoids generation of the block effect, but also can play the effect of code rate control in certain degree.

Description

Technical field: [0001] The invention relates to a method for preprocessing and removing block effects in low code rate video applications. Background technique: [0002] The noise contained in the source image input to the compression coding system not only affects the subjective and objective quality of the image, the accuracy of motion search during coding, but also leads to the increase of DCT high-frequency coefficients and reduces the coding efficiency. However, based on the filtering scheme without motion compensation, it will cause time-domain distortion in the motion area of ​​the video. In addition, due to the low bit-rate application of block-based video coding, when the quantization step size of adjacent blocks differs greatly, distortions such as block effect, mosquito noise (ring effect) and base image penetration effect will inevitably appear in the reconstructed image. The phenomenon seriously affects the visual effect of the reconstructed image (especially ...

AI Technical Summary

Problems solved by technology

[0002] The noise contained in the source image input to the compression coding system not only affects the subjective and objective quality of the image, the accuracy of motion search during coding, but also leads to the increase of DCT high-frequency coefficients and reduces the coding efficiency, etc.

The filtering scheme based on no motion compensation will cause temporal distortion in the motion area of ​​the video

In addition, due to the low bit-rate application of block-based video coding, when the quantization step size of adjacent blocks differs greatly, distortions such as block effect, mosquito noise (ring effect) and base image penetration effect will inevitably appear in the reconstructed image. Phenomenon, which seriously affects the visual effect of the reconstructed image (especially the block effect)

And when the encoder uses such a reconstructed frame with severe distortion as the reference frame of the subsequent frame, the distorted reference frame will not only affect the accuracy of motion estimation, but also increase the data volume of motion compensation residual information. As a result, the coding compression efficiency is seriously reduced

Whether it is the deblocking ring filter of H.263 or the post-processing deblocking filtering method introduced in MPEG-4 Appendix F, it is not only limited by the corresponding video coding standard (that is, the algorithm that is not specified in the coding standard cannot be used) , and cannot achieve the purpose of noise reduction and deblocking at the same time

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