映像情報メディア学会誌
Online ISSN : 1881-6908
Print ISSN : 1342-6907
ISSN-L : 1342-6907
65 巻 , 8 号
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  • 芦澤 恵太, 山谷 克
    2011 年 65 巻 8 号 p. 1201-1207
    発行日: 2011/08/01
    公開日: 2011/11/01
    ジャーナル フリー
    We propose a new image compression-decompression method that reproduces images with lower entropy (bit rates), particularly high-resolution images, than those processed by the DCT-based method at the same PSNR values. We predict each block by estimating the gradient, and then apply an orthogonal transformation to the prediction error. Our method is based on the Haar transform that requires only O(N) operations for an input signal of length N while the DCT requires O(N log2 N) operations. This advantage is particularly significant for images with a high-resolution. Our numerical experiments using 2048 × 2048 resolution images demonstrate the superiority of the proposed method over the DCT-based one.
  • 江本 正喜, 菅原 正幸, 日下部 裕一, 大村 耕平
    2011 年 65 巻 8 号 p. 1208-1214
    発行日: 2011/08/01
    公開日: 2011/11/01
    ジャーナル フリー
    In recent years, television systems with a wide field of view that offer an elevated sense of presence have been proposed. They have higher spatial resolutions than conventional systems. On the other hand, the effects of increasing the temporal resolution or frame rate of television systems have not yet been sufficiently investigated, with the exception of the effects of frame interpolation at the receiver. On the assumption that people will enjoy TV with wide field of view displays at home in the future, we conducted a quantitative analysis of the effects of increased frame rate by a subjective evaluation of moving picture quality. The results indicated that an increase in frame rate from 60 frames per second (fps) to 120 fps improved the evaluated quality by 0.46 rank and an increase from 120 to 240 fps improved quality by 0.23 rank, with statistical significance. The degree of improvement depended on the picture content.
  • 窪田 悟, 岸本 和之, 合志 清一, 今井 繁規, 五十嵐 陽一, 松本 達彦, 芳賀 秀一, 中枝 武弘, 馬野 由美, 小林 雄二
    2011 年 65 巻 8 号 p. 1215-1220
    発行日: 2011/08/01
    公開日: 2011/11/01
    ジャーナル フリー
    The preferred viewing distances for high definition television LCDs were measured as a function of the screen size, screen luminance and content of the displayed pictures. Although the screen size is the most dominant parameter, both it and the screen luminance significantly influence the preferred viewing distance, while the content of the displayed pictures does not. The ratio of the viewing distance preferences to the screen height (H) decreases with the size of the screen. The preferred viewing distance for a 24-inch display is a 5.9 H for a screen luminance (peak white luminance) of 200cd/m2. Similarly, that for a 65-inch display is a 3.9 H. The preferred viewing distance for a screen luminance of 200cd/m2 can be described Using the following empirical equation: D = (2.73 S + 75) /S. This is where D is the preferred viewing distance in screen height and S is the diagonal screen size in inches, where S is larger than or equal to 24 and smaller than or equal to 65. In this paper, these results are compared with the field survey data of the practical viewing distances in home environments. We also discuss the optimum screen size and viewing conditions of high definition television LCDs in actual home environments.
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