H.264运动估计算法的研究
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摘要
据统计，人类每天通过视觉获取的信息约占外界信息总量的70％左右，视频信息在多媒体信息中占有重要地位；同时视频数据冗余度最大，经压缩处理后的视频质量高低直接决定了多媒体服务的质量。可以说，多媒体应用的核心技术就是数字视频技术，也就是说多媒体技术获得使用的关键技术之一就是解决视频、音频数字化后数据量大与数据存储媒体和通信网容量小的矛盾，最好的解决方法就是压缩，因此对视频编码的研究已成为信息技术领域的重点。
新一代标准H.264是由ITU-T视频编码专家组VCEG(Video Coding Experts Group)和ISO/IEC运动图象专家组MPEG(Moving Picture Experts Group)共同制定的视频编码标准，这一编码标准可获得很高的编码效率，尤其是在低码率方面比MPEG-4有明显提高，适合低宽带、高质量网络视频应用的需要。为了方便H.264在低码率高时性应用系统中的实现，须对其编码算法进行优化。经过对H.264编码器的分析可以得出，运动估计是视频压缩编码中的核心技术之一，采用运动估计和运动补偿技术可消除视频信号的时间冗余以提高编码效率。因此，如何提高运动估计的效率，使运动估计算法搜索过程更健壮、更快速、更高效成为目前研究的热点之一。
本文介绍了视频编码标准及其基本原理，描述了H.264新的特性及关于运动估计的相关知识，并通过对几种运动估计算法的分析比较，提出一种改进的运动估计算法；新算法是在UMHexagonS(Unsymmetrical-Cross Muti-Hexagon Search)算法的基础上，增加一个与内容相关的自适应阈值，以判断是否可立即结束搜索，保证了原算法率失真性能，并且进一步降低了算法的运算量。在H.264参考软件模型JM8.6下，经过VC++6.0编译，实现该算法，通过仿真，将该算法与UMHexagonS算法的性能进行了比较。测试结果表明，改进的运动估计算法在保证图象质量的前提下，提高了大约10％的编码速度。
According to the data, people capture about 70 percent information coming from vision, so video information is very important in multimedia; at the same time, video data has much redundancy, the key factor of multimedia's service quality is the video quality after compression. The key technology of multimedia application is Digital Video, That is to say the key technology of the use of multimedia is solving the conflict of the data and the communications networks, and the solution of which is compression. So the encoding of video is the key technology of information field.
The emerging H.264 advanced video coding standard (H.264/AVC) achieves significant improvement in coding efficiency compared with the previous standards. This standard can obtain excellent coding efficiency and outperforms the MPEG-4 in the low bit rate environment. So it can meet the requirement of the network-video with low bandwidth and high quality. Motion estimation is one of the core techniques of video coding. Motion estimation and motion compensation can reduce the large amount of temporal redundancy that exists between frames of video sequences, which leads to high compression. The research on looking for a motion estimation algorithm that can get an effective and accurate motion vector quickly becomes a hot topic at present.
This thesis introduces video en/decode standards and their principles, and describes the new coding feature of the H.264 and the basic knowledge of Motion Estimation. After investigating scores of algorithms, this article has summarized all the algorithms completely and introduces an improved ME search algorithm. The improved ME search algorithm is on the base of algorithm UMHexagonS, and it adds a threshold so can judge whether to terminate the search or not. The improved algorithm ensures the original algorithm's performance, at the same time, reduces the operation. The simulations use the JM8.6 software model as the main source. Simulation results show that the improved ME algorithm ensured the quality of the picture, and enhanced the coding speed about 10%.
新一代标准H.264是由ITU-T视频编码专家组VCEG(Video Coding Experts Group)和ISO/IEC运动图象专家组MPEG(Moving Picture Experts Group)共同制定的视频编码标准，这一编码标准可获得很高的编码效率，尤其是在低码率方面比MPEG-4有明显提高，适合低宽带、高质量网络视频应用的需要。为了方便H.264在低码率高时性应用系统中的实现，须对其编码算法进行优化。经过对H.264编码器的分析可以得出，运动估计是视频压缩编码中的核心技术之一，采用运动估计和运动补偿技术可消除视频信号的时间冗余以提高编码效率。因此，如何提高运动估计的效率，使运动估计算法搜索过程更健壮、更快速、更高效成为目前研究的热点之一。
本文介绍了视频编码标准及其基本原理，描述了H.264新的特性及关于运动估计的相关知识，并通过对几种运动估计算法的分析比较，提出一种改进的运动估计算法；新算法是在UMHexagonS(Unsymmetrical-Cross Muti-Hexagon Search)算法的基础上，增加一个与内容相关的自适应阈值，以判断是否可立即结束搜索，保证了原算法率失真性能，并且进一步降低了算法的运算量。在H.264参考软件模型JM8.6下，经过VC++6.0编译，实现该算法，通过仿真，将该算法与UMHexagonS算法的性能进行了比较。测试结果表明，改进的运动估计算法在保证图象质量的前提下，提高了大约10％的编码速度。
According to the data, people capture about 70 percent information coming from vision, so video information is very important in multimedia; at the same time, video data has much redundancy, the key factor of multimedia's service quality is the video quality after compression. The key technology of multimedia application is Digital Video, That is to say the key technology of the use of multimedia is solving the conflict of the data and the communications networks, and the solution of which is compression. So the encoding of video is the key technology of information field.
The emerging H.264 advanced video coding standard (H.264/AVC) achieves significant improvement in coding efficiency compared with the previous standards. This standard can obtain excellent coding efficiency and outperforms the MPEG-4 in the low bit rate environment. So it can meet the requirement of the network-video with low bandwidth and high quality. Motion estimation is one of the core techniques of video coding. Motion estimation and motion compensation can reduce the large amount of temporal redundancy that exists between frames of video sequences, which leads to high compression. The research on looking for a motion estimation algorithm that can get an effective and accurate motion vector quickly becomes a hot topic at present.
This thesis introduces video en/decode standards and their principles, and describes the new coding feature of the H.264 and the basic knowledge of Motion Estimation. After investigating scores of algorithms, this article has summarized all the algorithms completely and introduces an improved ME search algorithm. The improved ME search algorithm is on the base of algorithm UMHexagonS, and it adds a threshold so can judge whether to terminate the search or not. The improved algorithm ensures the original algorithm's performance, at the same time, reduces the operation. The simulations use the JM8.6 software model as the main source. Simulation results show that the improved ME algorithm ensured the quality of the picture, and enhanced the coding speed about 10%.
引文
[1] ITU-T Recommendation H. 261. "Video codec for Audiovisual Services at pX64 kbit/s, "March 1993.
[2] ITU-T Recommendation H. 263, "Video Coding for Low bit rate Communication," version 1, Nov. 1995; version 2, Jan. 1998; version 3, Nov. 2000.
[3] 袁冰，刘辉新一代视频压缩标准H264的研究和应用有线电视技术2005．45～47．
[4] 李秀兰H．26x系列视频编码标准的进展及特点电脑知识与技术2005．48～49．
[5] ISO/IEC. IS 13818-2: Information technology-Generic coding of moving pictures and associated audioinformation-part 2; Video, 1995. (MPEG-2 Video).
[6] ISO/IEC. IS 14496-2: Information technology-Generic coding of audio-visual objects-part 2: Visual. December 1999. (MPEG-4 Video).
[7] P. I. Hosur and K. K. Ma, "Motion vector field adaptive fast motion estimation," in Proc. 2nd Int. Conf. Information, Communications and Signal Processing (ICICS'99), Singapore, Dec. 7-10, 1999.
[8] Zhibo Chen, Peng Zhou, Yun He, "Fast Integer Pel and Fractional Pel Motion Estimation for JVT", JVT-F017rl. doc, Joint Video Team (JVT) of ISO/IEC MPEG&ITU-T VCEG, 6th meeting, Awaji, Island, JP, 5-13 December, 2002
[9] Zhibo Chen, Peng Zhou, Yun He, "Fast Motion Estimation for JVT", JVT-G016. doc, Joint Video Team (JVT) of ISO/IEC MPEG & ITU-T VCEG, 7th Meeting: Pattaya Ⅱ, Thailand, 7-14 March, 2003
[10] JM8. 6, H. 264/AVC Software Coordination, http://bs.hhi.de/～suehrine/tml/.
[11] JVT Editors (T. Wiegand, G. Sullivan, A. Luthra), Draft ITU-T Recommendation and finaldraft international standard of joint video specification (ITU-T Rec. H. 264|ISO/IEC 14496-10AVC), JVT-G050rl, Geneva, May 2003.
[12] G Sullivan and T. Wiegand, Video Compression—From Concepts to the H. 264/AVC Standard, Proc. of the IEEE, Special Issue on Advances in Video Coding and Delivery, December 2004, invited paper.
[13] Ahmed, N., T. Natarajan, and K. R. Rao. Discrete cosine Transform. IEEE Trans. Computer(1974), 23: 90-93.
[14] Taki Y, Hatori M, Tanaka S. Interframe coding that follows the motion. Proceedings of IECEJ(Institute of Electronics and Communication Engineers of Japan) Annual Convention, 1974: 1263
[15] Brofferio S, Cafforio C, Del Re P, Quaglia G, Racciu A, Rocea F. Redundancy Reduction of Video Signals Using Movement Compensation. Alta Frequenza, 1974: 836～843
[16] Giorda F, Racciu A. Bandwidth Reduction of Video Signals via Shift Vector Transmission. IEEE Trans. On Comm., 1975: 1002-1004
[17] [英]Iain E．G．Richardson 著 欧阳合 韩军 译．视频编解码器设计．国防科技大学出版社，2005-01．
[18] Haralick. R. M. and J. S. Lee. The facet approach to optical flow. In Image Understanding Workshop(1993): 125-130
[19] Lee, O., and Y Wang. Motion compensated prediction using nodal based deformable block matching. Journal of Visual Communications and Image Representation(March 1995), 6: 26-34
[20] Seferidis, V, and M. Ghanbari. General approach to block matching motion estimation. Optical Engeering (July 1993), 32: 1464-1474
[21] Wang, Y and O. Lee. Active mesh- a feature seeking and tracking image sequence representation scheme. IEEE Trans. Image Process. (Sept. 1994), 3: 610-624
[22] Bierling, M, Displacement estimation by hierarchical block matching. In SPIE Conf. Visual Commun. Image Processing (Nov. 1988), SPIE-1001: 942-951
[23] Yao Wang, Jorn Ostermann and Ya-qin Zhang. Video Processing and Communication. P: 194-203
[24] Wiegand T, Sullivan G, Bjontegaard G. Overview of the H. 264/AVC Video Coding Standard. IEEE Trans on Circuitsand Systems for Video Technology, 2003, 13: 560～576.
[25] 毕厚杰．新一代视频压缩编码标准—H．264／AVC．人民邮电出版社2005-05．
[26] 梁亚玲，刘静，杜明辉．H．264 中块运动估计及其发展趋势．电视技术，2005增刊：40-43．
[27] Ce Zhu, Xiao Lin, and Lap-Pui Chau. Hexagon-BasedSearch Patten for Fast Block Motion Estimation," IEEETrans. on CSVT, Vol. 12, pp. 349-355, May, 2002.
[28] Ce ZHu, Xiao Lin, Lappui CHau, and Lai-Man Po. Enhanced Hexagonal Search for Fast Block Motion Estimation. IEEE Trans on Circuitsand Systems for Video Technology, Vol. 14, pp. 1210-1214, Oct. 2004.
[29]. Alex is M. Tourapis, O. C . A u, M. L. Liou. Predictive motion vector field adaptive search technique (PMVFAST)-enhancing block based motion estimation. Visual Communications and Image Processing 2001(VCIP-2001), San Jose, CA, 2001
[30] .A. M. Tourapis, O. C. Au, and M. L. Liou, "Highly Efficient Predictive Zonal Algorithmsfor Fast Block-Matching Motion Estimation," IEEE Transactions on Circuits and Systems for Video Technology, Vol. 12, No 2, pp.934-947, Oct'02.
[31] Liang Yaling,Liu Jing,Du Minghui. A Cross Octagnal Search Algorithm For Fast Block Motion Estimation. Proceedings of 2005 International Symposium on Intelligent Signal Processing and Communication Systems:357-360,Dec.2005.
[2] ITU-T Recommendation H. 263, "Video Coding for Low bit rate Communication," version 1, Nov. 1995; version 2, Jan. 1998; version 3, Nov. 2000.
[3] 袁冰，刘辉新一代视频压缩标准H264的研究和应用有线电视技术2005．45～47．
[4] 李秀兰H．26x系列视频编码标准的进展及特点电脑知识与技术2005．48～49．
[5] ISO/IEC. IS 13818-2: Information technology-Generic coding of moving pictures and associated audioinformation-part 2; Video, 1995. (MPEG-2 Video).
[6] ISO/IEC. IS 14496-2: Information technology-Generic coding of audio-visual objects-part 2: Visual. December 1999. (MPEG-4 Video).
[7] P. I. Hosur and K. K. Ma, "Motion vector field adaptive fast motion estimation," in Proc. 2nd Int. Conf. Information, Communications and Signal Processing (ICICS'99), Singapore, Dec. 7-10, 1999.
[8] Zhibo Chen, Peng Zhou, Yun He, "Fast Integer Pel and Fractional Pel Motion Estimation for JVT", JVT-F017rl. doc, Joint Video Team (JVT) of ISO/IEC MPEG&ITU-T VCEG, 6th meeting, Awaji, Island, JP, 5-13 December, 2002
[9] Zhibo Chen, Peng Zhou, Yun He, "Fast Motion Estimation for JVT", JVT-G016. doc, Joint Video Team (JVT) of ISO/IEC MPEG & ITU-T VCEG, 7th Meeting: Pattaya Ⅱ, Thailand, 7-14 March, 2003
[10] JM8. 6, H. 264/AVC Software Coordination, http://bs.hhi.de/～suehrine/tml/.
[11] JVT Editors (T. Wiegand, G. Sullivan, A. Luthra), Draft ITU-T Recommendation and finaldraft international standard of joint video specification (ITU-T Rec. H. 264|ISO/IEC 14496-10AVC), JVT-G050rl, Geneva, May 2003.
[12] G Sullivan and T. Wiegand, Video Compression—From Concepts to the H. 264/AVC Standard, Proc. of the IEEE, Special Issue on Advances in Video Coding and Delivery, December 2004, invited paper.
[13] Ahmed, N., T. Natarajan, and K. R. Rao. Discrete cosine Transform. IEEE Trans. Computer(1974), 23: 90-93.
[14] Taki Y, Hatori M, Tanaka S. Interframe coding that follows the motion. Proceedings of IECEJ(Institute of Electronics and Communication Engineers of Japan) Annual Convention, 1974: 1263
[15] Brofferio S, Cafforio C, Del Re P, Quaglia G, Racciu A, Rocea F. Redundancy Reduction of Video Signals Using Movement Compensation. Alta Frequenza, 1974: 836～843
[16] Giorda F, Racciu A. Bandwidth Reduction of Video Signals via Shift Vector Transmission. IEEE Trans. On Comm., 1975: 1002-1004
[17] [英]Iain E．G．Richardson 著 欧阳合 韩军 译．视频编解码器设计．国防科技大学出版社，2005-01．
[18] Haralick. R. M. and J. S. Lee. The facet approach to optical flow. In Image Understanding Workshop(1993): 125-130
[19] Lee, O., and Y Wang. Motion compensated prediction using nodal based deformable block matching. Journal of Visual Communications and Image Representation(March 1995), 6: 26-34
[20] Seferidis, V, and M. Ghanbari. General approach to block matching motion estimation. Optical Engeering (July 1993), 32: 1464-1474
[21] Wang, Y and O. Lee. Active mesh- a feature seeking and tracking image sequence representation scheme. IEEE Trans. Image Process. (Sept. 1994), 3: 610-624
[22] Bierling, M, Displacement estimation by hierarchical block matching. In SPIE Conf. Visual Commun. Image Processing (Nov. 1988), SPIE-1001: 942-951
[23] Yao Wang, Jorn Ostermann and Ya-qin Zhang. Video Processing and Communication. P: 194-203
[24] Wiegand T, Sullivan G, Bjontegaard G. Overview of the H. 264/AVC Video Coding Standard. IEEE Trans on Circuitsand Systems for Video Technology, 2003, 13: 560～576.
[25] 毕厚杰．新一代视频压缩编码标准—H．264／AVC．人民邮电出版社2005-05．
[26] 梁亚玲，刘静，杜明辉．H．264 中块运动估计及其发展趋势．电视技术，2005增刊：40-43．
[27] Ce Zhu, Xiao Lin, and Lap-Pui Chau. Hexagon-BasedSearch Patten for Fast Block Motion Estimation," IEEETrans. on CSVT, Vol. 12, pp. 349-355, May, 2002.
[28] Ce ZHu, Xiao Lin, Lappui CHau, and Lai-Man Po. Enhanced Hexagonal Search for Fast Block Motion Estimation. IEEE Trans on Circuitsand Systems for Video Technology, Vol. 14, pp. 1210-1214, Oct. 2004.
[29]. Alex is M. Tourapis, O. C . A u, M. L. Liou. Predictive motion vector field adaptive search technique (PMVFAST)-enhancing block based motion estimation. Visual Communications and Image Processing 2001(VCIP-2001), San Jose, CA, 2001
[30] .A. M. Tourapis, O. C. Au, and M. L. Liou, "Highly Efficient Predictive Zonal Algorithmsfor Fast Block-Matching Motion Estimation," IEEE Transactions on Circuits and Systems for Video Technology, Vol. 12, No 2, pp.934-947, Oct'02.
[31] Liang Yaling,Liu Jing,Du Minghui. A Cross Octagnal Search Algorithm For Fast Block Motion Estimation. Proceedings of 2005 International Symposium on Intelligent Signal Processing and Communication Systems:357-360,Dec.2005.