在JPEG2000 中, Rate control 利用了將影像分割成比sbbband 還要小的code-block, 以及在每個code-block 中分層處理的特性。使得ratecontrol 在實作上極為容易實行, 而且也能達到相當不錯的結果。就分成code-block 而言, 不同的code-block size 可以導致不同的效果; 例如: 要達到較好的壓縮效率, 比較好的方式是使用最小的code-block。另一方面, code-block 的size 愈大, 所需要用來描述各個code-block 的headers和terminations 就愈少; 反之,則需要愈多。而且, 較小的code-block 會導致較少的null block 以及在高頻的時候浪費太多bytes 在描述對影像品質影響不大的bits。Headers, terminations 及壓縮效率都會影響rate control的執行結果, 最好是headers, terminations 愈小, 而壓縮效率愈高愈好。然而如果採用JPEG2000 中的作法, 根本無法達到這樣的目標。

　　所以, 一個新的方法是採用較大的code-block 以及較小的contextblock 來搭配。這種作法的好處在於, 可以把大的code-block 視為一群小的code-block 的集合。用來描述code-block 的headers 及terminations可以用大的方式來看。另外, 編小的code-block 可以達到較好的壓縮效率。此外, 因為使用了新的code-block 來編碼, 一個新的演算法也是必要的。所以, 在這篇論文當中, 也提出一個基於新code-block 方法而發展出來的更有效率的演算法。

　　The features of EBCOT and quantization make the rate control in JPEG2000 easy to implement and also has good performance. However, since the EBCOT is not perform once on the whole image but on bit-planes of each code-block, the selection of code-block size is an critical. A code-block of large size will need less headers. On the other hand, the smallest, 4*4, code-block can conduct best compression efficiency. Another problem that exists in the larger code-block is it large unnecessary bytes contribution by the ‘Significant Pass’. The ‘Significant Pass’ may generates many bytes that do not contributes to the improvement of image quality. Also, the adjusting of different quantization step, which may possible improve the compression efficiency, though with the price of image quality losing. The serious image quality losing is not preferred in application of rate control.

　　An idea is thus developed that encodes the largest, 64*64, code-block size with small context blocks. The proposed method is to encode a larger code-block with the small context block. This is approaches by dividing the large code-block into several small context blocks. Thus the encoding of the large code-block can be seen as encode a group of smaller code-block in the context sense while only one header is applied to describe the large code-block. The division of larger context block into smaller ones will also improve the compression efficiency because of its higher possibility to encode null block. In addition, the context division method will even resolve the problem of unreasonable bytes contribution by the ‘Significant Pass’ which has less quality improvement, since bits on the context blocks’ boundary can be removed from ‘Significant Pass’. Thus the context block dividing method will obtain a much better performance of rate control than the original scheme in JPEG2000.

[1] Pankaj Batra,Modeling and efficient optimization for object-based scalability and some related problems,IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 9, NO. 10, OCTOBER 2000

[2] Marek Doman¡¦ski,Adam luczak,Slawomir MackowiakSpatio-temporal scalability for MPEG video coding,IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 10, NO. 7, OCTOBER 2000

[3] Jiangtao Wen, Max Luttrell, and John Villasenor,Trellis-based R-D optimal quantization in H.263 plus,IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 9, NO. 8, AUGUST 2000

[4] Kenneth Rose,Shankar L. Regunathan,Toward optimality in scalable predictive coding,IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 10, NO. 7, JULY 2001

[5] Mihaela van der Schaar,Hayder Radha,A hybrid temporal-SNR fine-granular scalability for Internet videoIEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 11, NO. 3, MARCH 2001

[6] Stephane, G. Mallat,A Theory for Multiresolution Signal Decomposition: The Wavelet Representation,IEEE,Transaction on Pattern and Machine Inteligence,Vol 11,No.7,July 1999

[7] Robert Hsu, T. Sumitomo, H Harashima, Tube-based video coding,Image Communication 9(1997),249~266

[8] Stephen A. Martucci,Iraj Sodagar,Tihao Chiang,Ya-Qin Zhang,A Zerotree Wavelet Video Coder,IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 7, NO. 1, FEBRUARY 1997

[9] Pao-Chi Chang and Ta-Te Lu,A Scalable Video Compression Technique Based on Wavelet Transform and MPEG Coding,IEEE Transaction on Consumer Electrionics, Vol.45, No.3, August 1999

[10] Gregory J. Conklin and Sheila S. Hemami,A COMPARISON OF TEMPORAL SCALABILITY,IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 9, NO. 6, SEPTEMBER 1999

[11] Qingwen Hu and Sethuraman Panchanathan,Image/Video Spatial Scalability in Compressed Domain,IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 45, NO. 1, FEBRUARY 1998

[12] Ulrich Benzler,Spatial Scalable Video Coding Using a Combined Subband-DCT Approach,IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 10, NO. 7, OCTOBER 2000

[13] Hong Man, Faouzi Kossentini, and Mark J. T. Smith, “A Family of Efficient and Channel Error-Resilience Wavelet/Subband Image Coders,” IEEE Trans. On Circuit and System for Video Technology, vol. 9 no. 1, FEB 1999. CA, USA, 96CH35919, 1996, vol. 2, pp. 109–112.Processing, vol. 5, no.4, pp. 565-574, April 1996.

[14] J. Wen and J. Villasenor, “A class of reversible variable length codes for robust image and video coding,” Proc. 1997 IEEE Int. Conf. Image Proc., Santa Barbara, CA, Oct. 1997, pp. II-65-II-68.

[15] W. Pennebaker and J. Mitchell, “JPEG Still Image Compression Standard,” New York: Van Nostrand Reinhold, 1993.

[16] W. Sweldens, “The lifting scheme: construction of second generation wavelets,”SIAM J. Math. Anal., vol. 29, no.2, pp 511-546, 1997.

[17] David Taubman, EBCOT: Embedded Block Coding with Optimized Truncation,ISO/IEC JTC/SC 29/ WG 1N 1684, April 2000.

[18] David Taubman, “Embedded Block Coding in JPEG2000,” Proc. of IEEE International Conference on Image Processing, Vancouver, Canada, 2000, vol. 2, pp. 33-36

[19] Kuan-Fu Chen, Chung-Jr Lian and Hong-Hui Chen, Liang-Gee Chen, “Analysis and Architecture Design of EBCOT for JPEG2000,” 2001 IEEE

[20] W. B. Pennebaker and J. L. Mitchell, “Probability estimation for Q-Coder,” IBM J. Res. Develop. Vol. 32 no.6 November 1988

[21] W. B. Pennebaker and J. L. Mitchell, “Software Implementations of the Q-Coder,” IBM J. Res. Develop. Vol. 32 November 1988

[22] W. B. Pennebaker and J. L. Mitchell, “Optimal Hardware and Software Arithmetic Coding Procedures for the Q-Coder,” IBM J. Res. Develop. Vol. 32 no. 6, November 1988