AVS视频编码中帧间预测算法及全零块检测研究
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摘要
随着人们对多媒体信息需求的日益增长,多媒体技术的发展突飞猛进。作为多媒体技术的核心,视频处理技术也得到了高速发展。大量的视频数据对传输带宽和储存空间都提出了很高的要求,所以对视频数据进行压缩化的视频编解码技术已经成为国内外研究和工业应用的热点之一。AVS (Advanced Audio-Video Coding-Decoding Standard)是我国“数字音视频编解码技术标准工作组”自主研发的第二代音视频编码标准,是当前世界上最先进的音视频编码标准之一,并且具有我国自主的知识产权。AVS具有复杂度低,压缩比高,图像质量高,应用范围广,专利费低等优点,代表着我国数字音视频产业的技术水平及发展方向。本文对AVS编码器的核心算法进行了改进,并进行了代码实现,显著提高了编码器的编码性能。
本文介绍了AVS视频编解码标准的编码原理,编码流程及其关键技术,包括：帧间预测、帧内预测、亚像素差值、整数变换与量化、环路滤波、熵编码等等。将AVS视频编解码标准与国外主流标准H.264／AVC进行对比,从技术水平与实际应用两方面说明了AVS标准在国内音视频产业中的发展潜力。之后,以编解码技术标准工作组提供的编码器参考模型rm52j为参考模型,进行了模块结构和代码实现的整体介绍,从而为接下来的算法改进与实现建立坚实的理论知识基础。
在参考模型中,帧间预测所采用的是传统的率失真优化模式选择算法,需要遍历所有帧间预测模式,所以会占用大量的时间与系统资源。本文提出了一种将时域与纹理相结合的快速帧间预测模式选择算法,结合了原始视频图像序列中图像之间的时域相关性,跳过宏块预判和宏块自身的纹理特性,从多个方面实现了对模式选择算法的优化。对于背景相对固定的视频序列或者运动相对激烈的视频序列都有明显的速度提升,在保证视频本身编码性能的前提下,显著节省了编码时间。
根据AVS标准中整数变换的特点,本文采用了一种基于8×8离散整数余弦变换的一种有效的全零块判别准则,并推导出了相应的全零块检测门限。全零块检测是面向低比特率的视频编码器常用的优化方法之一,特别是与基于跳过宏块预判的帧间模式预测相结合,可以省去变换、量化、反变换、反量化、块重建等所带来的大量计算。在保证视频图像质量和比特率几乎不变的情况下,大幅度节省编码时间。将全零块的检测算法应用到运动估计阶段,能够减少运动搜索的次数,提高运动估计效率,增强编码器的性能。
For the increasing demand of multimedia information, the multimedia technology is developing very quickly. As the core of multimedia technology, video processing technology is quick developing too. A large number of video data has put forward a very high demand of transmission bandwidth and storage space, so the video codec technology which encodes and decodes the video sequence has become one of the hot issues of the research and industrial application. AVS (Advanced Audio-Video Coding-Decoding Standard) video standard is developed by the Audio Video Coding Standard Working Group of China, which is one of the most advanced video compression standards available and has the own intellectual property rights. AVS has low complexity, high compression ratio, high image quality, wide application range, low patent cost. This paper carries out AVS video encode optimization in aspects of structural adjustment, source code optimization and optimized implementation of core algorithm. These lead to obvious raise in encoding efficiency.
An introduction is given which is about the encode principle and encode flow of AVS video codec standard, together with the key technologies, including inter prediction, intra prediction, sub-pixel interpolation, transform and quantization, loop filter and entropy coding, etc. The comparison between AVS and H.264/AVC which is the most popular video codec standard abroad is given. Then, based on the reference software rm52j provided by AVS video codec technology standard group, we do the structural and source code introduction, which will provide foundation for the following algorithm improvement and code implement.
Rate distortion optimization mode decision is used in AVS standard. All the modes of inter prediction will be traversed, which results in severely time-consuming. A fast inter prediction mode decision algorithm based on the time and texture characteristic of macroblocks. Speed improvement is very obvious for both video with fixed background and fast-motion video. This algorithm can save the coding time obviously while maintaining the coding performance.
According to the characteristic of integral transform, this paper uses an efficient all-zero block determination rule for 8×8 integral discrete Cosine transform and the corresponding threshold. All-zero detection is one of the common optimization methods oriented towards low bit rate video coding, especially when combined with inter mode prediction based on skip blocks prediction. By using the algorithm the time would be reduced greatly which taken by implementing transform, quantization, inverse transform, inverse quantization and block reconstruction with negligible loss of PSNR and increment of bit rate. Using all zero block detection algorithm in motion estimation will reduce the times of motion search, improve motion estimation efficiency and enhance the encode performance.
本文介绍了AVS视频编解码标准的编码原理,编码流程及其关键技术,包括：帧间预测、帧内预测、亚像素差值、整数变换与量化、环路滤波、熵编码等等。将AVS视频编解码标准与国外主流标准H.264／AVC进行对比,从技术水平与实际应用两方面说明了AVS标准在国内音视频产业中的发展潜力。之后,以编解码技术标准工作组提供的编码器参考模型rm52j为参考模型,进行了模块结构和代码实现的整体介绍,从而为接下来的算法改进与实现建立坚实的理论知识基础。
在参考模型中,帧间预测所采用的是传统的率失真优化模式选择算法,需要遍历所有帧间预测模式,所以会占用大量的时间与系统资源。本文提出了一种将时域与纹理相结合的快速帧间预测模式选择算法,结合了原始视频图像序列中图像之间的时域相关性,跳过宏块预判和宏块自身的纹理特性,从多个方面实现了对模式选择算法的优化。对于背景相对固定的视频序列或者运动相对激烈的视频序列都有明显的速度提升,在保证视频本身编码性能的前提下,显著节省了编码时间。
根据AVS标准中整数变换的特点,本文采用了一种基于8×8离散整数余弦变换的一种有效的全零块判别准则,并推导出了相应的全零块检测门限。全零块检测是面向低比特率的视频编码器常用的优化方法之一,特别是与基于跳过宏块预判的帧间模式预测相结合,可以省去变换、量化、反变换、反量化、块重建等所带来的大量计算。在保证视频图像质量和比特率几乎不变的情况下,大幅度节省编码时间。将全零块的检测算法应用到运动估计阶段,能够减少运动搜索的次数,提高运动估计效率,增强编码器的性能。
For the increasing demand of multimedia information, the multimedia technology is developing very quickly. As the core of multimedia technology, video processing technology is quick developing too. A large number of video data has put forward a very high demand of transmission bandwidth and storage space, so the video codec technology which encodes and decodes the video sequence has become one of the hot issues of the research and industrial application. AVS (Advanced Audio-Video Coding-Decoding Standard) video standard is developed by the Audio Video Coding Standard Working Group of China, which is one of the most advanced video compression standards available and has the own intellectual property rights. AVS has low complexity, high compression ratio, high image quality, wide application range, low patent cost. This paper carries out AVS video encode optimization in aspects of structural adjustment, source code optimization and optimized implementation of core algorithm. These lead to obvious raise in encoding efficiency.
An introduction is given which is about the encode principle and encode flow of AVS video codec standard, together with the key technologies, including inter prediction, intra prediction, sub-pixel interpolation, transform and quantization, loop filter and entropy coding, etc. The comparison between AVS and H.264/AVC which is the most popular video codec standard abroad is given. Then, based on the reference software rm52j provided by AVS video codec technology standard group, we do the structural and source code introduction, which will provide foundation for the following algorithm improvement and code implement.
Rate distortion optimization mode decision is used in AVS standard. All the modes of inter prediction will be traversed, which results in severely time-consuming. A fast inter prediction mode decision algorithm based on the time and texture characteristic of macroblocks. Speed improvement is very obvious for both video with fixed background and fast-motion video. This algorithm can save the coding time obviously while maintaining the coding performance.
According to the characteristic of integral transform, this paper uses an efficient all-zero block determination rule for 8×8 integral discrete Cosine transform and the corresponding threshold. All-zero detection is one of the common optimization methods oriented towards low bit rate video coding, especially when combined with inter mode prediction based on skip blocks prediction. By using the algorithm the time would be reduced greatly which taken by implementing transform, quantization, inverse transform, inverse quantization and block reconstruction with negligible loss of PSNR and increment of bit rate. Using all zero block detection algorithm in motion estimation will reduce the times of motion search, improve motion estimation efficiency and enhance the encode performance.
引文
[1]ITU-T, "Video Codec for Audio Visual Service at P×64 kbit/s"[c], ITU-T Recommendation H.261, Nov,1990.
[2]ITU-T, Video Coding for Very Low Bit Rate Communication[C], ITU-T Recommendation H.263, version 2,Jan.1998.
[3]ITU-T Recommendation H.261:"Video codec for Audio Visual services at P X 64 kbit/s", Geneva,1990, revised at Helsinki, March 1993.
[4]ISO/IEC JTC1, Coding of Moving Pictures and Associated Audio for Digital Storage Media at Up to About 1.5Mbit/s-Part2:Video[S], ISO/IEC 11172,1993.
[5]ISO/IEC, Information Technology-Generic Coding of Moving Pictures and Associated Audio Information:Video[S], ISO/IEC 13818,1995.02.
[6]Joint Video Specification(ITU-T Rec.H.264|ISO/IEC 14496-10 AVC)-Joint Committee Drafts Joint Video Team(JTV)of ISO/IEC MPEG and ITU-T VCEG 7th Meeting:Pattaya,Thailand, March 2003.
[7]Iain E G Richardson.H.264/MPEG-4 Part 10 White Paper [S].2003.01.
[8]ITU-T, Video Coding for Very Low Bit Rate Communication[C],ITU-T Recommendation H.263, version 1,Nov.1995.
[9]http://www.avs.org.cn.
[10]翁慈洁,张悠慧,汪东升.H.264中指数哥伦布算法的优化实现研究计算机工程与设计2007年第12期2867-2869
[11]毕厚杰,新一代视频压缩编码标准H.264／AVC,北京-人民邮电出版社2005
[12]Wen Gao AVS Standard-Audio Video Coding Standard Workgroup of China The 14th Annual Wireless and Optical Communications Conference-April 22-23,2005.
[13]Iain E.G.Richardson.H.264和MPEG-4视频压缩——新一代多媒体的视频编码技术(欧阳合,韩军).长沙：国防科技大学出版社,2004
[14]J.Rissanen and GGLandgon,Jr., "Arithmetic coding," IBM J.Res. Dev., vol. 23,no.2,pp149-162,Mar.1979
[15]K.R.Rao and P.Yip,Discrete Cosine Transform,Academic Press,1990
[16]D.Huffman,A method for the construction of minimum redundancy codes, Proc of the IRE,40,pp.1098-1101,1952
[17]S.W.Golomb,Run-length encoding,IEEE Trans.on Inf.Theory, IT-12, 1966:399-401
[18]数字音视频编码技术标准工作组.信息技术先进音视频编码第2部分：视频(GB／T 200090.2-2006).中国国家标准化管理委会,2006
[19]姚栋,虞露.H.264指数哥伦布码解码部件的硬件设计和实现[J].电视技术,2004(11)：14-17
[20]连元冠,石玥,夏军,尹涵春AVS和H.264编码性能的比较电视技术,2007年第31卷第3期
[21]HM Wong,O.C Au, and A.Chang. Fast Sub-pixel Inter-prediction Based on the Texture Direction Analysis. Proc. IEEE International Symposium, Circuits and Systems, Oct 2005.
[22]Wei Zhenyu,Jiang Baochen,Zhang Xudong,Chen Yu.A New Full-pixel and Sub-pixel Motion Vector Search Algorithm for Fast Block-matching Motion Estimation in H.264.Image and Graphics,Dec.2004.
[23]Libo Yang,Keman Yu,Jiang Li,and Shipeng Li.Prediction-based directional fractional pixel motion estimation for H.264 video coding.Proc. of ICASSP 2005,March 2005.
[24]Christos Grecos, Ming Yuan Yang.Fast Inter Mode Prediction for P Slice in the H.264 Video Coding Standard. IEEE Tramaction On Broandcasting, June,2005
[25]Jeyun Lee, Byeungwoo Jeon. Fast Mode Decision for H.264.Proc.ICME,2004.
[26]X Jing, L P Chau. Fast approach for H.264 inter mode decision.Electronics Letters,2004.
[27]Ming Yang,Wenbeng Wang.Fast Macroblock Mode Selection Based On Motion Content Classification in H.264,AVC.ICIP'2004.Oct 2004.
[28]Yu Andy C,Efficient Block-size Selection Algorithm For Inter-frame coding In H.264/MPEG-4 AVC. Proc. ICASSP,2004.
[29]Byeungwoo Jeon, Jeyun Lee. Fast Mode Decision for H.264. Joint Video Team(JVT)of ISO/IEC MPEG and ITU-T VCEG2003.
[30]Zhi Zhou, Mingting Sun. Fast Macroblock Inter Mode Decision and Motion Estimation for H.264/MPEG-4 AVC, ICIP'2004, Oct 2004.
[31]Peng Yin, Hye-Yeon Cheong Tourapis, Alexis Michael Tourapis. Fast Mode Decision and Motion Estimation For JVT/H.264. ICIP'2003. Sept 2003.
[32]Zhenyu Wei, King Ngi Ngan. A Fast Macroblock Mode Decision Algorithm for H.264. IEEE Asia Pacific Conference on 4-7 Dec.2006.
[33]Byeungwoo Jeon, Jeyun Lee. Fast Mode Decision for H.264. Joint Video Team(JVT)of ISO/IEC MPEG and ITU-T VCEG,2003.
[34]Yu Andy C, Efficient Block-size Selection Algorithm For Inter-frame coding In H.264/MPEG-4 AVC. Proc. ICASSP,2004.
[35]Hanli Wang,Sam Kwong, Chi-Wah Kok. An Efficient Mode Decision Algorithm for H.264/AVC Encoding Optimization. Multimedia,IEEE Transactions on Volume 9,Issue 4,June 2007.
[36]钟玉琢,王琪,贺玉文.基于对象的多媒体数据压缩编码国际标准MPEG-4及其校验模型.北京：科学出版社,2000.
[37]F.Pan,X.Lin,S.Rahardja,etal. Fast Mode Decision Algorithm for JVT Intra Prediction. JVT-G013,7th JVT Meeting, Pattaya Ⅱ, Thailand, March 2003
[38]Liang Fan,Siwei Ma,Feng Wu. Overview of AVS Video Standard[C]. Proe.2004 IEEE Intl. Conf. Multimedia&Expo, PP.423-426,2004.
[39]T.Wiegand, G.Sullivan. Overview of the H.264/AVC video coding stand[J]. IEEE Trans on circuits and system for video technology,13(7),2003.
[40]周韬,H.264视频编码中全零块检测技术及其应用研究,国防科学技术大学硕士学位论文,2007年.
[41]Li Fu-jiang, Zhang Gang, Predictive skip mode based all zero block detection for AVS encoder, ISECS International Colloquium,2009.
[42]游娜,AVS视频编码器优化及模式选择算法研究,山东大学硕士学位论文,2009年.
[43]Yangsoo Kim,Yoonsik Choe,Yungho Choi. Fast Mode Decision Algorithm for H.264 using AZCB Prediction Consumer Electronics,2006. ICCE'06.2006 Digest of Technical Papers. International Conference on 7-1 1 Jan.2006.
[44]滕国伟,H.264／AVC实时编码系统及其相关算法的研究,上海大学博士学位论文,2005.
[45]王维东,姚庆栋,刘鹏.小数像素运动估计快速算法,通信学报,2003.
[46]H.Malvar,A.Hallapuro, M.Karczewicz, and L.Kerofsky, Low-complexity transform and quantization in H.264/AVC, IEEE Circuits Syst. Video Technol. Vol.13, July 2003.
[47]王一皓,H.264帧内、帧间预测与变换模块的研究及FPGA实现,电子科技大学硕士学位论文,2007年04月
[48]T.J.Klausutis and V.K.Madisetti, Variable block size adaptive lapped transform-based image coding, in Proc. IEEE Int. Conf. Image Processing ICIP'97,Vol,3,Vashington,DC,Oct 1997.
[49]虞露,胡倩,易峰.AVS视频的技术特征,电视技术,2005年第7期
[50]Malvar H.S, Hallapuro A, Karczewicz M, Kerofsky.L, Low-complexity transform and quantization in H.264/AVC,IEEE Transactions on Circuits and Systems for Video Technology,Volume 13, Issue 7,July 2003.
[51]Huangqiang Zeng, Canhui Cai, Fast Mode Decision for H.264/AVC Based on Macroblock Motion Activity, IEEE Transactions on Circuits and Systems for Video Technology, Volume 19, April 2009.
[52]S.Zhu, K.K.Ma, A new Diamond Search Algorithm for Fast Block Matching Motion Estimation. Ieee Trans. Image Processing,2000.
[2]ITU-T, Video Coding for Very Low Bit Rate Communication[C], ITU-T Recommendation H.263, version 2,Jan.1998.
[3]ITU-T Recommendation H.261:"Video codec for Audio Visual services at P X 64 kbit/s", Geneva,1990, revised at Helsinki, March 1993.
[4]ISO/IEC JTC1, Coding of Moving Pictures and Associated Audio for Digital Storage Media at Up to About 1.5Mbit/s-Part2:Video[S], ISO/IEC 11172,1993.
[5]ISO/IEC, Information Technology-Generic Coding of Moving Pictures and Associated Audio Information:Video[S], ISO/IEC 13818,1995.02.
[6]Joint Video Specification(ITU-T Rec.H.264|ISO/IEC 14496-10 AVC)-Joint Committee Drafts Joint Video Team(JTV)of ISO/IEC MPEG and ITU-T VCEG 7th Meeting:Pattaya,Thailand, March 2003.
[7]Iain E G Richardson.H.264/MPEG-4 Part 10 White Paper [S].2003.01.
[8]ITU-T, Video Coding for Very Low Bit Rate Communication[C],ITU-T Recommendation H.263, version 1,Nov.1995.
[9]http://www.avs.org.cn.
[10]翁慈洁,张悠慧,汪东升.H.264中指数哥伦布算法的优化实现研究计算机工程与设计2007年第12期2867-2869
[11]毕厚杰,新一代视频压缩编码标准H.264／AVC,北京-人民邮电出版社2005
[12]Wen Gao AVS Standard-Audio Video Coding Standard Workgroup of China The 14th Annual Wireless and Optical Communications Conference-April 22-23,2005.
[13]Iain E.G.Richardson.H.264和MPEG-4视频压缩——新一代多媒体的视频编码技术(欧阳合,韩军).长沙：国防科技大学出版社,2004
[14]J.Rissanen and GGLandgon,Jr., "Arithmetic coding," IBM J.Res. Dev., vol. 23,no.2,pp149-162,Mar.1979
[15]K.R.Rao and P.Yip,Discrete Cosine Transform,Academic Press,1990
[16]D.Huffman,A method for the construction of minimum redundancy codes, Proc of the IRE,40,pp.1098-1101,1952
[17]S.W.Golomb,Run-length encoding,IEEE Trans.on Inf.Theory, IT-12, 1966:399-401
[18]数字音视频编码技术标准工作组.信息技术先进音视频编码第2部分：视频(GB／T 200090.2-2006).中国国家标准化管理委会,2006
[19]姚栋,虞露.H.264指数哥伦布码解码部件的硬件设计和实现[J].电视技术,2004(11)：14-17
[20]连元冠,石玥,夏军,尹涵春AVS和H.264编码性能的比较电视技术,2007年第31卷第3期
[21]HM Wong,O.C Au, and A.Chang. Fast Sub-pixel Inter-prediction Based on the Texture Direction Analysis. Proc. IEEE International Symposium, Circuits and Systems, Oct 2005.
[22]Wei Zhenyu,Jiang Baochen,Zhang Xudong,Chen Yu.A New Full-pixel and Sub-pixel Motion Vector Search Algorithm for Fast Block-matching Motion Estimation in H.264.Image and Graphics,Dec.2004.
[23]Libo Yang,Keman Yu,Jiang Li,and Shipeng Li.Prediction-based directional fractional pixel motion estimation for H.264 video coding.Proc. of ICASSP 2005,March 2005.
[24]Christos Grecos, Ming Yuan Yang.Fast Inter Mode Prediction for P Slice in the H.264 Video Coding Standard. IEEE Tramaction On Broandcasting, June,2005
[25]Jeyun Lee, Byeungwoo Jeon. Fast Mode Decision for H.264.Proc.ICME,2004.
[26]X Jing, L P Chau. Fast approach for H.264 inter mode decision.Electronics Letters,2004.
[27]Ming Yang,Wenbeng Wang.Fast Macroblock Mode Selection Based On Motion Content Classification in H.264,AVC.ICIP'2004.Oct 2004.
[28]Yu Andy C,Efficient Block-size Selection Algorithm For Inter-frame coding In H.264/MPEG-4 AVC. Proc. ICASSP,2004.
[29]Byeungwoo Jeon, Jeyun Lee. Fast Mode Decision for H.264. Joint Video Team(JVT)of ISO/IEC MPEG and ITU-T VCEG2003.
[30]Zhi Zhou, Mingting Sun. Fast Macroblock Inter Mode Decision and Motion Estimation for H.264/MPEG-4 AVC, ICIP'2004, Oct 2004.
[31]Peng Yin, Hye-Yeon Cheong Tourapis, Alexis Michael Tourapis. Fast Mode Decision and Motion Estimation For JVT/H.264. ICIP'2003. Sept 2003.
[32]Zhenyu Wei, King Ngi Ngan. A Fast Macroblock Mode Decision Algorithm for H.264. IEEE Asia Pacific Conference on 4-7 Dec.2006.
[33]Byeungwoo Jeon, Jeyun Lee. Fast Mode Decision for H.264. Joint Video Team(JVT)of ISO/IEC MPEG and ITU-T VCEG,2003.
[34]Yu Andy C, Efficient Block-size Selection Algorithm For Inter-frame coding In H.264/MPEG-4 AVC. Proc. ICASSP,2004.
[35]Hanli Wang,Sam Kwong, Chi-Wah Kok. An Efficient Mode Decision Algorithm for H.264/AVC Encoding Optimization. Multimedia,IEEE Transactions on Volume 9,Issue 4,June 2007.
[36]钟玉琢,王琪,贺玉文.基于对象的多媒体数据压缩编码国际标准MPEG-4及其校验模型.北京：科学出版社,2000.
[37]F.Pan,X.Lin,S.Rahardja,etal. Fast Mode Decision Algorithm for JVT Intra Prediction. JVT-G013,7th JVT Meeting, Pattaya Ⅱ, Thailand, March 2003
[38]Liang Fan,Siwei Ma,Feng Wu. Overview of AVS Video Standard[C]. Proe.2004 IEEE Intl. Conf. Multimedia&Expo, PP.423-426,2004.
[39]T.Wiegand, G.Sullivan. Overview of the H.264/AVC video coding stand[J]. IEEE Trans on circuits and system for video technology,13(7),2003.
[40]周韬,H.264视频编码中全零块检测技术及其应用研究,国防科学技术大学硕士学位论文,2007年.
[41]Li Fu-jiang, Zhang Gang, Predictive skip mode based all zero block detection for AVS encoder, ISECS International Colloquium,2009.
[42]游娜,AVS视频编码器优化及模式选择算法研究,山东大学硕士学位论文,2009年.
[43]Yangsoo Kim,Yoonsik Choe,Yungho Choi. Fast Mode Decision Algorithm for H.264 using AZCB Prediction Consumer Electronics,2006. ICCE'06.2006 Digest of Technical Papers. International Conference on 7-1 1 Jan.2006.
[44]滕国伟,H.264／AVC实时编码系统及其相关算法的研究,上海大学博士学位论文,2005.
[45]王维东,姚庆栋,刘鹏.小数像素运动估计快速算法,通信学报,2003.
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