基于H.264的解码算法优化
摘要
多媒体通信的迅猛发展对视频处理与传输提出了越来越高的要求。以交互式实时视频通信为代表的视频业务,由于其高带宽、低延时、低误码等要求使得视频业务成为整个多媒体通信的瓶颈。因此,视频压缩技术显得至关重要。
H.264/AVC是由ISO/IEC的运动图像专家组MPEG和ITU-T的视频编码专家组VCEG组成的联合视频小组JVT共同制定而成的最新的视频编码国际标准。H.264标准中包含了很多先进的视频压缩编码技术。与以前的视频编码标准相比,压缩性能有了明显的进步。在相同视觉感知质量的条件下,H.264的编码效率比MPEG-4提高了50%左右,并且有更好的网络友好性。然而,H.264的高压缩编码效率是以很高的计算复杂度为代价的,其解码复杂度约为MPEG-4简单配置的3倍以上,所以在实际应用中必须对算法进行优化以提高其解码的时间效率。
本文首先介绍了视频压缩的基本原理、方法,以及数字视频压缩标准的发展过程。接着,简要介绍了H.264解码器的主要功能模块。对H.264赖以获得高压缩性能的视频编码层中的主要技术做了较详细的介绍。
在对已有的CAVLC解码算法进行详细分析的基础上,本文提出了CAVLC快速解码算法。在分析已有快速滤波算法基础上,本文提出了基于宏块级帧场自适应模式的快速滤波算法。对本文所提出算法进行的大量实验表明,改进算法不但在很大程度上降低了运算量,提高了解码的时间效率,并且对图像的质量没有产生明显的影响。
The rapid development of multimedia communication demands more videoprocessing and transmission techniques. Digital video services, which are representedby interactive real-time video communication, are the bottle neck of multimediacommunication because of their high technical requirements such as broad band, lowdelayandlowbit errorrate.Inthiscase,agoodstandardisneededespeciallywhenthenetworkbandwidthsfortransportaretakentoaccount.
H.264/AVC is the newest international video coding standard. It was developedbyaJointVideoTeam(JVT)consistingofexperts from ITU-T'sVideoCodingExpertsGroup (VCEG) and ISO/IEC's Moving Picture Experts Group (MPEG). H.264 iscomposed of many advanced video coding techniques. Compared to existing videocoding standards, H.264 has made great progress in coding efficiency. For example, itimproves the compression efficiency by a factor of about 50% (on average) overMPEG-4. In addition, H.264 provides a very friendly network interface. However, theimprovement in compression efficiency of H.264 comes from the dramatic increase incomputational complexity; this makes it a must to reduce the computationalcomplexityofalgorithmsinH.264inrealtimeapplications.
In this paper, the fundamental principles, methods and the standardization processof video compression is first briefly presented, then,the main functional modules ofH.264 decoder are introduced, including entropy decoding, inverse scanning, scalingand transformation, intra prediction, inter prediction, deblocking and reference picturemanagement. In addition, the main techniques on which H.264 is based to achieve itshighcompressionefficiencyispresentedindetail.
Based on a thorough analysis of the existing CAVLC decoding algorithms, a fastCAVLC decodingalgorithm is proposedinthis paper. Basedon ananalysis ofexistingfast deblocking algorithms under MBAFF mode, a low complexity deblockingalgorithm is proposed. Extensive simulations on the methods proposed in this papershow, with little degradation in the decoded picture quality, the algorithms reducedramaticallythecomputationalload,andimprovedecodingefficiency.
H.264/AVC是由ISO/IEC的运动图像专家组MPEG和ITU-T的视频编码专家组VCEG组成的联合视频小组JVT共同制定而成的最新的视频编码国际标准。H.264标准中包含了很多先进的视频压缩编码技术。与以前的视频编码标准相比,压缩性能有了明显的进步。在相同视觉感知质量的条件下,H.264的编码效率比MPEG-4提高了50%左右,并且有更好的网络友好性。然而,H.264的高压缩编码效率是以很高的计算复杂度为代价的,其解码复杂度约为MPEG-4简单配置的3倍以上,所以在实际应用中必须对算法进行优化以提高其解码的时间效率。
本文首先介绍了视频压缩的基本原理、方法,以及数字视频压缩标准的发展过程。接着,简要介绍了H.264解码器的主要功能模块。对H.264赖以获得高压缩性能的视频编码层中的主要技术做了较详细的介绍。
在对已有的CAVLC解码算法进行详细分析的基础上,本文提出了CAVLC快速解码算法。在分析已有快速滤波算法基础上,本文提出了基于宏块级帧场自适应模式的快速滤波算法。对本文所提出算法进行的大量实验表明,改进算法不但在很大程度上降低了运算量,提高了解码的时间效率,并且对图像的质量没有产生明显的影响。
The rapid development of multimedia communication demands more videoprocessing and transmission techniques. Digital video services, which are representedby interactive real-time video communication, are the bottle neck of multimediacommunication because of their high technical requirements such as broad band, lowdelayandlowbit errorrate.Inthiscase,agoodstandardisneededespeciallywhenthenetworkbandwidthsfortransportaretakentoaccount.
H.264/AVC is the newest international video coding standard. It was developedbyaJointVideoTeam(JVT)consistingofexperts from ITU-T'sVideoCodingExpertsGroup (VCEG) and ISO/IEC's Moving Picture Experts Group (MPEG). H.264 iscomposed of many advanced video coding techniques. Compared to existing videocoding standards, H.264 has made great progress in coding efficiency. For example, itimproves the compression efficiency by a factor of about 50% (on average) overMPEG-4. In addition, H.264 provides a very friendly network interface. However, theimprovement in compression efficiency of H.264 comes from the dramatic increase incomputational complexity; this makes it a must to reduce the computationalcomplexityofalgorithmsinH.264inrealtimeapplications.
In this paper, the fundamental principles, methods and the standardization processof video compression is first briefly presented, then,the main functional modules ofH.264 decoder are introduced, including entropy decoding, inverse scanning, scalingand transformation, intra prediction, inter prediction, deblocking and reference picturemanagement. In addition, the main techniques on which H.264 is based to achieve itshighcompressionefficiencyispresentedindetail.
Based on a thorough analysis of the existing CAVLC decoding algorithms, a fastCAVLC decodingalgorithm is proposedinthis paper. Basedon ananalysis ofexistingfast deblocking algorithms under MBAFF mode, a low complexity deblockingalgorithm is proposed. Extensive simulations on the methods proposed in this papershow, with little degradation in the decoded picture quality, the algorithms reducedramaticallythecomputationalload,andimprovedecodingefficiency.
引文
[1]ITU-T,RecommendationH.261: VideoCodecforAudiovisual Services at px64bit/s,Mar1993.
[2]ISO/IEC JTCl/SC29/WG11, ISO/IEC, MPEG-1CommitteeDraft,CD11172:InformationTechnology.Dec.1991.
[3]ISO/IEC JTCl/SC29/WG11, ISO/IEC, MPEG-2CommitteeDraft,CD11172:InformationTechnology.Dec.1993.
[4]ITU-T, Recommendation H.263:Video Coding for Low Bitrate Communication,DraftITU-TRecommendationH.263.Mar1996.
[5]ISO/IEC JTCl/SC29/WG11, ISO/IEC, Coding of Audio-Visual Objects-Part2:Visual,ISOJEC14496-2(MPEG-4VisualVersion1),Apr1999.
[6]Study of Final Committee Draft of Joint Vide Specification (ITU-T Rec.H.264 |ISO/IEC 14496-10 AVC). Joint Video Team (JVT) of ISO/IEC MPEG&ITU-TVCEG(ISO/IEC JETI/SC29/WGII and ITU-T SG16 Q.6) 6th Meeting: Awaji,Island,JP,5-13December,2002
[7]A.M.Tekalp,DigitalVideoProcessingEnglewoodCliffs:PrinticeHall,1995
[8]周荫清,信息理论基础,北京:北京航空航天大学出版社,1993
[9]J.DGibson,T.Berger,T.Looabaughandetal.,“Digitalcompressionformultimediaprinciples&standards,”Copyright1997byMorganKaufmanPublishers,Inc.
[10]M.E. Al-Mualla, C.N. Canagarajah and D.R.Bull, “Video coding for mobilecommunications-efficiency, complexity and resilience.”Coprignt 2002 by ElsevierSinence(USA).
[11]ISO/IEC CD 11172, “Coding of moving pictures and associated audio for digitalstorage media at up to 1.5Mbits/sec—Part 2: Coding of moving pictures information,”Dec.1991
[12]Intel Corporation, “IA-32 IntelArchitecture SoftwareDeveloper’s Manual Volume3:ProgrammingGuide”OrderNumber245472,
[13]T. Wiegand and B. Girod. Multi-Frame Motion-Compensation Prediction forVideoTransmission.KluwerAcademicPublishers.Sept.2001
[14]P. List, A. Joch, J. Lainema, G. Bjontegard, M. Karczewicz. Adaptive DeblockingFilte.IEEETransactionsonCircuitsandSystemsfor-VideoTechnology,July2003.
[15]S.Wenger,M.M. Hannuksela, T.Stockhammer, RTP payload Format for H.264Video.http://www.ietf.org/internet-draft-ietf-av-rtp-h264-04.txt,February2004
[16]张颖,张济林.H264中CAVLC解码的分组优化.信号处理.2005年,第21卷第1 期.17-21.
[17]朱冬冬,戴琼海.H.264 解码 CAVLC 码表查找算法的改进.电视技术.2004(1)26-27.
[18]Di Wu, Wen Gao, Mingzeng Hu and Zhenzhou Ji, “AVLSI architecture design ofCAVLC decoder,”5th International Conference on ASIC, vol.2, pp.962- 965, Beijing,China,21-24Oct.2003.
[19]Y.H.Mgoon, G.Y.Kim and J.H.Kim, “An efficient decoding of CAVLC inH.264/AVC video coding standard,”Consumer Electronics, IEEE Transactions onVolume51, Issue3, Aug.2005Page(s):933–938
[20]蒋汉琪,朱秀昌. H.264 编码器中插值运算和整数变换的优化.南京邮电学院学报.2005(3),41-44.
[21]熊赟,于鸿洋.H264实时软件解码器的实现.中国有线电视.2005(6),562-565.
[22]陈维安,李典等.H.264软件解码器的优化.数据采集于处理.2005(4),493-498.
[23]HOROWIZ.M.H, JOCH A, KOSSENTINI F, et al. H.264/AVC Baseline ProfileDecoder Complexity Analysis[J]. IEEE. Transactions on Circuits and Systems forVideoTechnology,2003,13(7):704-716.
[24]张颖,刘济林,H.264中CAVLC解码的分组优化[J].信号处理,2005,21(1):20.
[25]T. Wiegand, H.Schwarz, A. Joch, F. Kossentini, J. G. Sullivan, Rate-constrainedCoder Control and Comparison ofVideo Coding Standards, IEEE Trans. Circuits Syst.VideoTechnol,v13,pp.688-703,July2003
[26]H.264去块滤波快速算法的设计与实现, 清华大学, 韩峥, 唐昆, 电视技术2006,7(6).
[2]ISO/IEC JTCl/SC29/WG11, ISO/IEC, MPEG-1CommitteeDraft,CD11172:InformationTechnology.Dec.1991.
[3]ISO/IEC JTCl/SC29/WG11, ISO/IEC, MPEG-2CommitteeDraft,CD11172:InformationTechnology.Dec.1993.
[4]ITU-T, Recommendation H.263:Video Coding for Low Bitrate Communication,DraftITU-TRecommendationH.263.Mar1996.
[5]ISO/IEC JTCl/SC29/WG11, ISO/IEC, Coding of Audio-Visual Objects-Part2:Visual,ISOJEC14496-2(MPEG-4VisualVersion1),Apr1999.
[6]Study of Final Committee Draft of Joint Vide Specification (ITU-T Rec.H.264 |ISO/IEC 14496-10 AVC). Joint Video Team (JVT) of ISO/IEC MPEG&ITU-TVCEG(ISO/IEC JETI/SC29/WGII and ITU-T SG16 Q.6) 6th Meeting: Awaji,Island,JP,5-13December,2002
[7]A.M.Tekalp,DigitalVideoProcessingEnglewoodCliffs:PrinticeHall,1995
[8]周荫清,信息理论基础,北京:北京航空航天大学出版社,1993
[9]J.DGibson,T.Berger,T.Looabaughandetal.,“Digitalcompressionformultimediaprinciples&standards,”Copyright1997byMorganKaufmanPublishers,Inc.
[10]M.E. Al-Mualla, C.N. Canagarajah and D.R.Bull, “Video coding for mobilecommunications-efficiency, complexity and resilience.”Coprignt 2002 by ElsevierSinence(USA).
[11]ISO/IEC CD 11172, “Coding of moving pictures and associated audio for digitalstorage media at up to 1.5Mbits/sec—Part 2: Coding of moving pictures information,”Dec.1991
[12]Intel Corporation, “IA-32 IntelArchitecture SoftwareDeveloper’s Manual Volume3:ProgrammingGuide”OrderNumber245472,
[13]T. Wiegand and B. Girod. Multi-Frame Motion-Compensation Prediction forVideoTransmission.KluwerAcademicPublishers.Sept.2001
[14]P. List, A. Joch, J. Lainema, G. Bjontegard, M. Karczewicz. Adaptive DeblockingFilte.IEEETransactionsonCircuitsandSystemsfor-VideoTechnology,July2003.
[15]S.Wenger,M.M. Hannuksela, T.Stockhammer, RTP payload Format for H.264Video.http://www.ietf.org/internet-draft-ietf-av-rtp-h264-04.txt,February2004
[16]张颖,张济林.H264中CAVLC解码的分组优化.信号处理.2005年,第21卷第1 期.17-21.
[17]朱冬冬,戴琼海.H.264 解码 CAVLC 码表查找算法的改进.电视技术.2004(1)26-27.
[18]Di Wu, Wen Gao, Mingzeng Hu and Zhenzhou Ji, “AVLSI architecture design ofCAVLC decoder,”5th International Conference on ASIC, vol.2, pp.962- 965, Beijing,China,21-24Oct.2003.
[19]Y.H.Mgoon, G.Y.Kim and J.H.Kim, “An efficient decoding of CAVLC inH.264/AVC video coding standard,”Consumer Electronics, IEEE Transactions onVolume51, Issue3, Aug.2005Page(s):933–938
[20]蒋汉琪,朱秀昌. H.264 编码器中插值运算和整数变换的优化.南京邮电学院学报.2005(3),41-44.
[21]熊赟,于鸿洋.H264实时软件解码器的实现.中国有线电视.2005(6),562-565.
[22]陈维安,李典等.H.264软件解码器的优化.数据采集于处理.2005(4),493-498.
[23]HOROWIZ.M.H, JOCH A, KOSSENTINI F, et al. H.264/AVC Baseline ProfileDecoder Complexity Analysis[J]. IEEE. Transactions on Circuits and Systems forVideoTechnology,2003,13(7):704-716.
[24]张颖,刘济林,H.264中CAVLC解码的分组优化[J].信号处理,2005,21(1):20.
[25]T. Wiegand, H.Schwarz, A. Joch, F. Kossentini, J. G. Sullivan, Rate-constrainedCoder Control and Comparison ofVideo Coding Standards, IEEE Trans. Circuits Syst.VideoTechnol,v13,pp.688-703,July2003
[26]H.264去块滤波快速算法的设计与实现, 清华大学, 韩峥, 唐昆, 电视技术2006,7(6).