Proceedings of the KOSOMBE Conference (대한의용생체공학회:학술대회논문집)
- Volume 1991 Issue 11
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- Pages.44-47
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- 1991
An Adaptive Transform Code for Images
적응 변환코드를 이용한 영상신호 압축
- Kim, Dong-Youn (Dept. of Medical Engineering, Yonsei Univ.) ;
- Lee, Kyung-Joung (Dept. of Medical Engineering, Yonsei Univ.) ;
- Yoon, Hyung-Ro (Dept. of Medical Engineering, Yonsei Univ.)
- Published : 1991.11.15
Abstract
There exists a transform trellis code that is optimal for stationary Gaussian sources and the squared-error distortion measure at all rates. In this paper, we train an asymptotically optimal version of such a code to obtain one which is matched better to the statistics of real world data. The training algorithm uses the M-algorithm to search the trellis codebook and the LBG-algorithm to update the trellis codebook. To adapt the codebook for the varying input data. we use two gain-adaptive methods. The gain-adaptive scheme 1, which normalizes input block data by its gain factor, is applied to images at rate 0.5 bits/pixel. When each block is encoded at the same rate, the nonstationarity among the block variances leads to a variation in the resulting distortion from one block to another. To alleviate the non-uniformity among the encoded image, we design four clusters from the block power, in which each cluster has its own trellis codebook and different rates. The rate of each cluster is assigned through requiring a constant distortion per-letter. This gain-adaptive scheme 2 produces good visual and measurable quality at low rates.
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