Visual picture quality

Abstract: An object of the present invention is to improve visual picture quality. A picture signal is divided into a plurality of macro blocks and coding is conducted in macro block units. The coding is conducted including quantization process by a quantization portion. A motion compensation portion outputs the quantity of motion, L, in macro block units. An average quantity of motion, L ave , of a reference picture stored in a frame memory is outputted from a division portion. A control portion compares the quantity of motion L with two reference values relative to the average quantity of motion L ave and makes a correction to lower the quantization step in the quantization portion for macro blocks whose quantity of motion L is between the reference values. Accordingly, picture quality is improved in part of picture where motion is small and deterioration of visual picture quality is noticeable. At the same time, since the correction is not applied to picture with such slow motion that deterioration of picture quality is small, redundancy of coded signal does not unnecessarily increase.

Abstract: In a picture signal coding/decoding method and a picture signal coding/decoding device, the compressibility and visual picture quality of the picture pattern whose inter field correlation of high frequency decreases and inter field correlation of low frequency remains when slow movement occurs are improved and transmitted. The intra field component separate coding is performed in each field on the first and second fields of picture signal respectively, and by preventing the effect of inter field movement in advance, the dropping of compressibility by the movement is avoided and furthermore, new blocks is constructed by the resultant low frequency components of two fields and since it is so arranged that the component separate coding is performed in the frame, low frequency components which are not easily affected by slow movement can be coded efficiently, and as a result, the compressibility for the picture containing slow movement can be increased.

Abstract: Perceptual image and video coders have been reported extensively in the literature with a recent survey listing sixteen representative PVCs (perceptual video coders) for single-view video coding, ten of which conform to H.263, MPEG-4 or H.264/AVC international standard. Successful approaches to perceptual picture coding are classified as perceptual predictive coding, perceptual quantization, rate-perceptual-distortion optimization (RpDO) and perception-based pre-, loop- and postfiltering. This contribution analyzes and examines the performance and tradeoffs of representative perceptual as well as traditional waveform based picture coding methods in terms of their effectiveness in quality constrained coding and RpDO criterion in the context of visual quality controlled or regulated visual communication, broadcasting, entertainment and consumer electronic products, systems and services or applications. Fundamental flaws of performance benchmarking using a rate-driven coding strategy are interrogated for visual quality assured services or user experience. It is revealed that while existing perceptual distortion measures (PDMs) successfully grade distortions corresponding to HVS (human visual system) perception, their quantitative correspondence, or lack of it, to discernible levels by human visual perception in terms of just-not-noticeable-difference (JNND), just-noticeabledifference level 1 (JND1), JND level 2 (JND2), etc. has not been thoroughly investigated nor established, and this motivates the related initial work reported in this paper. Issues and constraints of existing picture coding standards are discussed in the context of developing a future picture coding standard framework for constant visual picture quality systems and services.

Abstract: In a picture signal coding/decoding method and device, the compressibility and visual picture quality of the picture pattern whose inter-field correlation of high frequency decreases and inter-field correlation of low frequency remains by slow movements are improved and transmitted. The intra-field component separate coding is performed in each field on first and second fields of the picture signal (S21) and by preventing the effect of inter-field movement in advance, the dropping of compressibility by the movement is avoided and furthermore, new blocks are constructed by the resultant low frequency components (S24, S25) of the two fields. Since it is so arranged that the component separate coding is performed in the frame, low frequency components which are not easily affected by slow movement can be coded efficiently, and as a result, the compressibility for pictures containing slow movements can be increased.