Improvements to the JPEG-LS prediction scheme Authors: S. Bedi, E. A. Edirisinghe, and G. Grecos Source : Image and Vision Computing. Vol. 22, No. 1, 2004, pp Speaker: Chia-Chun Wu ( 吳佳駿 ) Date : 2004/09/08

2 Outline Introduction to JPEG-LS JPEG-LS prediction scheme Improvements JPEG-LS prediction scheme Experimental results Conclusions Comments

3 Introduction to JPEG-LS cbd a Pixel value x in original image Compute difference = x - cbd ax Encode using entropy coding  Determine predictive value for x with prediction scheme Determine predictive value for x with prediction scheme

4 JPEG-LS prediction scheme cbd ax  JPEG-LS predictive template

5 JPEG-LS prediction scheme ca bx ca ba ca bb Horizontal edge Vertical edge

6 JPEG-LS prediction scheme ca bx ca bb ca ba Vertical edge Horizontal edge

7 JPEG-LS prediction scheme ca bx ca ba+b-c

8 Improvements JPEG-LS cbd ax Diagonal edge T1=20, T2=0

9 Experimental results  Predictive mean squared error N = 9

10 Experimental results Table 1 PMSE values and lossless compression ratios of all test images, when compressed using JPEG-LS

11 Experimental results Fig. 1. Performance at T1 = 11

12 Experimental results Fig. 2. Performance at T1 = 19

13 Experimental results Fig. 3. Optimum performance graphs

14 Experimental results Table 2 Optimum performance and settings for proposed algorithm

15 Experimental results Fig. 4. Predictive error images (a) using JPEG-LS, (b) using proposed scheme

16 Conclusions It maintains the low complexity requirement of JPEG-LS standard. The proposed a modifications reduce the PMSE up to 15%.

17 Comments 如何根據影像不同的特性，動態的去調 整門檻值 T1 及 T2 ？ 是否可以利用統計分析的方法，去找出 適用於一般影像的門檻值 T1 及 T2 ？

18 Sample images Lena Baboon