TobepublishedinProceedingsofspieVol.4115.Seehttp://itSwww.epfl.ch/-dsanta/forthefinalreference marker )and the entropy coded data has been protected by the regular termination of the arithmetic coder combined with the error resilient termination and segment symbols. The overhead of these protections amount also to less than 1%. In both cases the bitstream header is transmitted without errors Table 4. PSNR, in dB, corresponding to average MSE, of 200 runs, of the decoded"cafe" image when transmitted over a noisy channel with bit error rates(BER)and compression bitrates, for JPEG baseline and JPEG 2000, wi reversible and non-reversible filters (JPEG 2000R and JPEG 2000NR, respectively) JPEG 2000R BBR0250.5 JPEG 2000NR JPEG 200250.5102.0025051.020 64262131.39382723.0626713191389321.94253930343723 e6224526013025360622992620297034852172511|2982829 le52037233525912580211123.0625824682042226122331967 le416021620165217.161614165716291167116.16153814491202 As it can be seen, the reconstructed image quality under transmission errors is higher for JPEG 2000 than JPEG, across all encoding bitrates and error rates. Although both suffer from severe degradation at moderately high error rates (i.e. le-4 and le-5), at lower ones(i.e. Ie-6)JPEG 2000 proves to be fairly robust. Also the visual quality of JPEG 2000 at these lower error rates is much higher than that of JPEG. In fact, the artifacts created by transmission errors under JPEG 2000 are of the same nature as those created by quantization. In the case of JPEG, when a transmission error occurs it is often entire 8x8 blocks that will be missing and/or misplaced and the bottom of the image will often be missing as well It should also be noted that at higher error rates(i.e. le-4), the reconstructed image quality in JPEG 2000 increases very little with increasing bitrate. This is due to the fact that in JPEG 2000 each sub-band block is coded by bitplanes. When the error rate is high enough almost all code-blocks are affected in the most significant bitplanes, which are transmitted first. When a particular bitplane is affected in a block, lower bitplanes cannot be decoded and are therefore useless. In the case of JPEG the problem is even worse: the higher the encoding bitrate the lower the decoded quality. This can be explained by the fact that in JPEG the error is at the block level at the most and therefore the density of error protection decreases with 4.6. Functionality Table 5 summarizes the results of the comparison of different algorithms from a functionality point of view. The table clearly shows that from this perspective, JPEG 2000 is the standard offering the richest set of features in an efficient manner and within an integrated algorithmic approach. In this table we refer to genericity, which is the ability to efficiently compress different types of imagery across a wide range of bitrates Table 5. Functionality matrix. A+ indicates that it is supported, the more"+"the more efficiently or better it is upported. a"-indicates that it is not supported I JPEG 2000 JPEG-LS JPEG MPEG-4 VTCPNG ++ I progressive bitstreams +++++ I Region of Interest(ROi) coding ++ arbitrary shaped objects low complexity 十++十+++ + error resilience +++ non-iterative rate control ++ ++ TTT MPEG-4 VTC, as JPEG 2000, is able to produce progressive bitstreams without any noticeable overhead. However, the atter provides more progres nd produces bitstreams that are parseable and that can be rather easily reorganized by a transcoder on the fly. Along the same lines, JPEG 2000 also provides random access (i.e. involving a minimal decoding) to the block level in each sub-band, thus making possible to decode a region of the image without having to decode it as a whole. These two features could be very advantageous in applications such as digital librariesTo be published in Proceedings of SPIE Vol. 4115. See http://ltswww.epfl.ch/~dsanta/ for the final reference. 8 marker) and the entropy coded data has been protected by the regular termination of the arithmetic coder combined with the error resilient termination and segment symbols. The overhead of these protections amount also to less than 1%. In both cases the bitstream header is transmitted without errors. Table 4. PSNR, in dB, corresponding to average MSE, of 200 runs, of the decoded “cafe” image when transmitted over a noisy channel with various bit error rates (BER) and compression bitrates, for JPEG baseline and JPEG 2000, with reversible and non-reversible filters (JPEG 2000R and JPEG 2000NR, respectively). JPEG 2000R JPEG 2000NR JPEG BER 0.25 0.5 1.0 2.0 0.25 0.5 1.0 2.0 0.25 0.5 1.0 2.0 0 22.64 26.21 31.39 38.27 23.06 26.71 31.91 38.93 21.94 25.39 30.34 37.23 1e-6 22.45 26.01 30.25 36.06 22.99 26.20 29.70 34.85 21.77 25.11 29.18 28.29 1e-5 20.37 23.35 25.91 25.80 21.11 23.06 25.8 24.68 20.42 22.61 22.33 19.67 1e-4 16.02 16.20 16.52 17.16 16.14 16.57 16.29 16.71 16.16 15.38 14.49 12.02 As it can be seen, the reconstructed image quality under transmission errors is higher for JPEG 2000 than JPEG, across all encoding bitrates and error rates. Although both suffer from severe degradation at moderately high error rates (i.e. 1e-4 and 1e-5), at lower ones (i.e. 1e-6) JPEG 2000 proves to be fairly robust. Also the visual quality of JPEG 2000 at these lower error rates is much higher than that of JPEG. In fact, the artifacts created by transmission errors under JPEG 2000 are of the same nature as those created by quantization. In the case of JPEG, when a transmission error occurs it is often entire 8x8 blocks that will be missing and/or misplaced and the bottom of the image will often be missing as well. It should also be noted that at higher error rates (i.e. 1e-4), the reconstructed image quality in JPEG 2000 increases very little with increasing bitrate. This is due to the fact that in JPEG 2000 each sub-band block is coded by bitplanes. When the error rate is high enough almost all code-blocks are affected in the most significant bitplanes, which are transmitted first. When a particular bitplane is affected in a block, lower bitplanes cannot be decoded and are therefore useless. In the case of JPEG the problem is even worse: the higher the encoding bitrate the lower the decoded quality. This can be explained by the fact that in JPEG the error is at the block level at the most and therefore the density of error protection decreases with an increase in bitrate. 4.6. Functionality Table 5 summarizes the results of the comparison of different algorithms from a functionality point of view. The table clearly shows that from this perspective, JPEG 2000 is the standard offering the richest set of features in an efficient manner and within an integrated algorithmic approach. In this table we refer to genericity, which is the ability to efficiently compress different types of imagery across a wide range of bitrates. Table 5. Functionality matrix. A “+” indicates that it is supported, the more “+” the more efficiently or better it is supported. A “-” indicates that it is not supported. JPEG 2000 JPEG-LS JPEG MPEG-4 VTC PNG lossless compression performance +++ ++++ + - +++ lossy compression performance +++++ + +++ ++++ - progressive bitstreams +++++ - ++ +++ + Region of Interest (ROI) coding +++ - - + - arbitrary shaped objects - - - ++ - random access ++ - - - - low complexity ++ +++++ +++++ + +++ error resilience +++ ++ ++ +++ + non-iterative rate control +++ - - + - genericity +++ +++ ++ ++ +++ MPEG-4 VTC, as JPEG 2000, is able to produce progressive bitstreams without any noticeable overhead. However, the latter provides more progressive options and produces bitstreams that are parseable and that can be rather easily reorganized by a transcoder on the fly. Along the same lines, JPEG 2000 also provides random access (i.e. involving a minimal decoding) to the block level in each sub-band, thus making possible to decode a region of the image without having to decode it as a whole. These two features could be very advantageous in applications such as digital libraries