Showing papers by "Zhibo Chen published in 2008"

A novel image/video coding method based on Compressed Sensing theory

Abstract: Compressed sensing (CS) has been proposed for more efficient signal compression and recovery at theoretical level. This paper proposes a new image/video coding approach combining the CS theory into the traditional discrete cosine transform (DCT) based coding method to achieve better compression efficiency for spatially sparse signal. Furthermore, this new approach is integrated into JPEG and H.264/AVC coding framework as a new coding mode. Rate-distortion optimization is employed for adaptive selection between the new coding mode and the conventional coding modes. Experimental results demonstrated remarkable coding gain for different kinds of natural image/videos by the proposed method.

Method for lossless compressing prefix-suffix-codes, method for decompressing a bit sequence representing integers or symbols encoded in compressed prefix-suffix-codes and storage medium or signal carrying compressed prefix-suffix-codes

Abstract: The invention is related to lossless compression of prefix- suffix-codes wherein a prefix comprises unary code, and to corresponding decompression. The method for lossless compressing prefix-suffix-codes (VLCl, VLC2, VLC3) comprises the steps of forming a first contiguous bit sequence (FBS) from the prefixes (PRFXl, PRFX2, PRFX3), and lossless compressing the first contiguous bit sequence (FBS) by removing redundancy related to the difference between the first value's frequency in the first contiguous bit sequence (FBS) and the second value's frequency in the first contiguous bit sequence (FBS). Bit values are unevenly distributed in the prefixes while distribution of bit values in the suffixes is more even. Therefore, better compression is achievable if the prefixes are compressed separately.

A multiple description image/video coding method by compressed sensing theory

Abstract: Multiple description coding (MDC) has emerged as a promising approach to enhance the error resilient property for video transmission. This paper proposes a novel MDC method by incorporating a newly appeared signal recovery theory, compressed sensing (CS) theory, into image/video coding framework. The compressed sensing theory states that under certain conditions, a signal can be precisely reconstructed from only a small set of measurements. Taking this advantage, the proposed MDC method generates multiple descriptions in the frequency domain, enabling each description to recover original signals properly and the more descriptions the better quality. Experiments have demonstrated the feasibility and advantage of the proposed MDC scheme.

A Comparative Review of Aspect Ratio Conversion Methods

Abstract: The Aspect ratio is the fractional relation of the width of a video image compared to its height. Because of the historical and some other factors, there are so many video formats with different aspect ratios and the conversion of aspect ratio is required more and more imminently. The paper introduced all the aspect ratio conversion methods published in literatures, including cropping method, expanding method and so on, and presented experiment results to demonstrate the advantages and disadvantages of each conversion method.

A fast adaptive quantization matrix selection method in H.264/AVC

Abstract: Adaptive quantization matrix selection (AQMS) method was recently proposed in ITU-T VCEG to improve video coding performance. As a reference model for VCEG, this method involves coding a frame multiple times to obtain optimal candidate matrix parameters. In this paper, the method in AQMS is analyzed and an fast adaptive quantization matrix selection method is proposed. The proposed method keeps the quantization matrix selection in the macroblock level but removes the iterative quantization matrix parameter calculation in the frame level. Therefore, computational complexity is greatly reduced while the coding gain is maintained.

Aspect Ratio Conversion Based on Saliency Model

Abstract: The Aspect ratio is the fractional relation of the width of a video image compared to its height. The paper is focused on solving the problem that how to play various kinds of videos on the device screen with different aspect ratio from them. It is the first time to introduce saliency model, which can take human attention into account, into the aspect ratio conversion. Based on the saliency model, we proposed a novel cropping mode and a novel un-unique expanding mode, and then combine the two modes according to some principles from media aesthetics. Experiment results show that there is no distortion in the region of interest and no loss will be noticed in the output video sequences, which demonstrates the effectiveness and efficiency of our approach.

Method for encoding an image, method for decoding an image, encoder, decoder and signal or storage medium carrying an encoded image

Abstract: The invention relates to a method for encoding an image, a method for decoding an image, an encoder, a decoder and a signal or a storage medium carrying an encoded image. Said decoding method comprises de-quantizing the current index value by determining, by help of one or more neighbouring index values, a current context of a current index value and selecting a de-quantization value from a set of reconstruction values (-x 0 '', -x 0' , x 0 , x 0 ', x 0 '') wherein the selection depends on the current context. By context-dependent de-quantization of the current index value, quality loss due to quantization to said current index value is reduced.

Method and apparatus for entropy encoding blocks of transform coefficients of a video signal using a zigzag scan sequence, and method and apparatus for a corresponding decoding

Abstract: A key in efficient image compression is to explore source correlation so as to find a compact representation of coded image data. For encoding DCT transformed and quantised pixel blocks, based on statistical properties of such DCT transform, the coefficient blocks are scanned in a known zigzag line sequence. According to the invention, when combining DCT with DWT by DCT transforming DWT coefficient blocks, the DCT coefficient blocks of the LH, HL and HH subbands of the DWT blocks are scanned using a different zigzag scan for each one of these subbands, followed by entropy encoding.