Enhanced aacPlus编解码器的研究和实现
摘要
Enhanced aacPlus是目前最完美的、开放的低码率音频编码方案。为了满足移动通信、因特网流媒体以及数字广播市场新应用的需求，本文对Enhanced aacPlus编解码器的技术原理和实现方法作了深入的研究。论文首先介绍了音频编码技术的发展以及基本原理，然后详细分析研究了Enhanced aacPlus的结构框架和主要的算法模块。在尽量不降低音频质量的前提下，为了提高编解码性能，对Enhanced aacPlus编解码的算法采用了一些改进和优化措施。例如在心理声学模型中，采用CMDCT滤波器组来替代FFT滤波器组，利用谱平面法来进行音调侦测；在滤波器组模块中采用MDCT、IMDCT快速算法；在量化编码模块中采用一种新的单循环模式；对SBR和PS分别采用低能量工具和QMF滤波器组等等。实验结果显示，Enhanced aacPlus能够在低比特率下获得高质量的音频效果。
Enhanced aacPlus is the state-of-the-art low bit rate open standards audio codec. In this paper, the principle and implementation method of Enhanced aacPlus codec are studied deeply in order to enabling new applications in the markets of mobile, Internet streaming and digital broadcasting. A brief introduction to the development and the fundamental principle of audio coding technology is firstly carried out. Subsequently, the standard function blocks of Enhanced aacPlus are introduced, also the main algorithm techniques of the key modules is discussed in detail. Some important algorithmic modifications and optimizations are used to improve encoding performance and speed without reducing the audio quality. For example, the modification method used CMDCT filterbank instead of FFT filerbank and employed spectral flatness measure to detect tonality for the psychoacoustic model, developed a fast MDCT algorithm for filter bank tool, designed a new single loop structure for quantization module, used a low power SBR tool and QMF-based implementation of PS codec. Finally, the test results show that Enhanced aacPlus achieved excellent audio quality at low bitrate.
Enhanced aacPlus is the state-of-the-art low bit rate open standards audio codec. In this paper, the principle and implementation method of Enhanced aacPlus codec are studied deeply in order to enabling new applications in the markets of mobile, Internet streaming and digital broadcasting. A brief introduction to the development and the fundamental principle of audio coding technology is firstly carried out. Subsequently, the standard function blocks of Enhanced aacPlus are introduced, also the main algorithm techniques of the key modules is discussed in detail. Some important algorithmic modifications and optimizations are used to improve encoding performance and speed without reducing the audio quality. For example, the modification method used CMDCT filterbank instead of FFT filerbank and employed spectral flatness measure to detect tonality for the psychoacoustic model, developed a fast MDCT algorithm for filter bank tool, designed a new single loop structure for quantization module, used a low power SBR tool and QMF-based implementation of PS codec. Finally, the test results show that Enhanced aacPlus achieved excellent audio quality at low bitrate.
引文
[1] 卢官明，宗防．数字音频原理及应用．机械工业出版社，2005．1．
[2] 王炳锡．语音编码．西安电子科技大学出版社，2002．6．
[3] 张益贞，刘滔．Visual C++实现MPEG／JPEG编解码技术．人民邮电出版社，2002．
[4] ISO/IEC 11172-3. Information Technology-Coding of Moving Picture and Associated Audio for Digital Storage Media at up to About 1.5Mbit/s-part: 3. ISO/IEC JTC1/SC29 WG11, 1993
[5] ISO/IEC 13818-3. Information Technology-Generic Coding of Moving Picture and Associated Audio Information-Part 3: Audio. ISO/IEC JTC 1/SC29 WG11, 1998
[6] ISO/IEC 13818-7. Information Technology-Generic Coding of Moving Picture and Associated Audio Information-Part 7: Advanced Audio Coding(AAC). ISO/IEC JTC1/SC29 WG11, 1999.
[7] ISO/IEC 14496-3. Information Technology-Coding of Audio-Visual Objects-Part 3: Audio. ISO/IEC JTC1/SC29 WG11, 2001.
[8] ISO/IEC 14496-3: 2001/AMD1. Bandwidth Extension. ISO/IEC JTC1/SC29 WG11, 2003
[9] ISO/IEC 14496-3: 2001/AMD2. Parametric Audio Extension. ISO/IEC JTC1/SC29 WG11, 2004.
[10] 3GPP TS 26.401. Enhanced aacPlus general audio codec; General description. March 2005.
[11] 3GPP TS 26.402. Enhanced aacPlus general audio codec; Additional Decoder Tools. September 2005.
[12] 3GPP TS 26.403. Enhanced aacPlus general audio codec; Encoder Specification AAC Part. September 2004.
[13] 3GPP TS 26.404. Enhanced aacPlus general audio codec; Encoder Specification SBR Part. September 2004.
[14] 3GPP TS 26.405. Enhanced aacPlus general audio codec; Encoder Specification Parametric Stereo Part. March 2005.
[15] 李栋．MPEG-4音频编码标准 广播与电视技术，2001．12．
[16] 武银枝．基于DSP的MPE6-4 LD-AAC编码器的实现．西安电子科技大学硕士研究生学位论文，2005．1．
[17] 陈艳阳．MPEG-2AAC低复杂度双声道编解码器的DSP实现．东南大学硕士研究生学位论文，2001．3．
[18] 张艳．基于定点DSP的MPEG-4 AAC实时编解码系统研究．成都理工大学硕士研究生学位论文，2005．5．
[19] 汪斌．音频编解码算法及软硬件协同设计研究．浙江大学博士研究生学位论文，2004．5．
[20] 杨斌．AAC编码器的优化实现 西安交通大学硕士研究生学位论文，2003．3．
[21] 朱丽．心理声学模型算法改进．中国科学技术大学硕士学位论文，2003．5．
[22] 梁彬．时频技术及其在音频压缩编码中的应用．东南大学硕士研究生学位论文，2000．3．
[23] 徐盛．基于感知理论的低码率高质量音频编码．上海交通大学博士研究生学位论文，2000．6．
[24] 何兵．低码率感知音频编码研究．上海交通大学博士研究生学位论文，2002．2．
[25] 车振华．MPEG-2 AAC音频编码算法分析及其DSP实现．东南大学硕士研究生论文，2002．3．
[26] E. Schuijers, J. Breebaart, H. Purnhagen, and J. Engdegard. Low Complexity Parametric Stereo Coding. AES 116th Convention, Berlin, Germany, May 2004.
[27] H. Purnhagen. Low Complexity Parametric Stereo Coding in MPEG-4. Proc. of the 7th International Conference on Digital Audio Effects(DAFX-04), Naples, Italy, October 2004.
[28] M. Wolters, K. Kjorling, D. Homm, and H. Purnhagen. A Closer Look into MPEG-4 High Efficiency AAC. AES 115th Convention, New York, NY, USA, October 2003.
[29] M. Dietz, L. Liljeryd, K. Kjorling, and O. Kunz. Spectral Band Replication, A Novel Approach in Audio Coding. AES 112th Convention, Munich, Germany, May 2002.
[30] P. Ekstrand. Bandwidth Extension of Audio Signals by Spectral Band Replication. Proc. of the 1st IEEE Benelux Workshop on Model bansed Processing and Coding of Audio(MPCA-2002), Leuven, Belgium, November 2002, pp. 73-79.
[31] D. Frerichs. New MPEG-4 High-efficiency AAC Audio: Enabing New Applications. April 2003, download from http://www.mpegif.org.
[32] R. G.. v. d. Waal, R. N. J. Veldhuis. Subband coding of stereophonic digital audio signals. Proc. IEEE Int. Conf. on Acoustics, Speech, Signal Processing, Toronto, Ontario, Canada, April 1991.
[33] P. Duhamel, Y. Mahieux, and J. P. Petit. A fast algorithm for the implementation of filter banks based on "Time Domain Aliasing Cancellation". Proc. IEEE Int. Conf. on Acoustics, Speech, Signal Processing, 1991, vol. 3, pp. 2209-2212.
[34] T. Painter, A. Spanias. A Review of Algorithms for Perceptual Coding of Digital Audio Signals. Proc. of 13th Int. Conf. on Digital Signal Processing, July 1997, vol. 1, pp. 79-208.
[35] M. Dietz, S. Melzer. CT-aacplus-a State Of The Art Audio Coding Scheme. EBU Technical Review, No. 291, July 2002.
[36] A. Servetti, A. Rinotti, and J. C. D. Martin. Fast implementation of the MPEG-4 AAC main and low complexity decoder. Proc. of IEEE Int. Conf. on Acoustics, Speech, Signal Processing, 2004, pp. 249-252.
[37] I. Dimkovi, D. Milovanovi, Z. Bojkovi. Fast Software Implementation of MPEG Advanced Audio Encoder. 2002 14th Int. Conf. on Digital Signal Processing, vol. 2, pp. 839-843.
[38] E. Kurniawati, C. T. Lau, B. Premkumar. New Implementation Techniques of an Efficient MPEG Advanced Audio Coder. 2004 IEEE Transaction on Consumer Electronics, Vol: 50, No: 2.
[39] Y. Yakamizawa, T. Nomura, M. Ikekawa. High-Quality and Processor-Efficient Implementation of an MPEG-2 AAC Encoder. Proc. IEEE Int. Conf. on Acoustics, Speech, Signal Processing, 2001, Vol. 2, pp. 985-988.
[40] 岳玲，陈健，徐盛．MPEG-4AAC解码器在TMS320C6416上的实现．电声技术，2003．11．
[41] I. Dimkovic. Improved ISO AA C Coder.(from Internet)
[42] J. Herre, J. D. Johnston. Enhancing the Performance of Perceptual Audio Coders by Using Temporal Noise Shaping(TNS). AES 101 Convention, Los Angeles, 1996.
[43] J. Herre. Temporal Noise Shaping, Quantization and Coding Methods in Perceptual Audio Coding: A Tutorial Introduction. AES 17th Int. Conf. on High Quality Audio Coding, September 1999, pp 17-31.
[44] J. D. Johnston. Estimation of Perceptual Entropy Using Noise Masking Criteria. Proc. of IEEE Int. Conf. on Acoustics, Speech, and Signal Processing, 1998, pp. 2524-2527.
[45] A. D. Duefias, R. Pérez, B. Rivas, E. Alexandre, and A. S. Pena. A robust and efficient implementation of MPEG-2/4 AAC Natural Audio Coders. AES 112th Convention, Munich, Germany, May 2002.
[46] V. Prakash, A. Magadum. Optimal Fixed Point Implementation of MPEG-4 AAC Encoder. International Signal Processing Conference, Mar 31-Apr 3, 2003, Dallas, Texas, U. S. A.
[47] J. Engdegard, H. Purnhagen, J. Rodén, and L. Liljeryd. Synthetic Ambience in Parametric Stereo Coding. AES 116th Convention, Berlin, Germany, May 2004.
[48] J. Breebaart, S. v. d. Par, A. Kohlrausch, and E. Schuijers. Parametric Coding of Stereo Audio. EURASIP Journal on Applied Signal Processing 2005: 9, 1305-1322.
[49] J. Breebaart, S. v. d. Par, A. Kohlrausch, and E. Schuijers. High-quality Parametric Spatial Audio Coding at Low Bitrates. AES 116th Convention, Berlin, Germany, May 2004.
[50] J. Herre. From Joint Stereo to Spatial Audio Coding-Recent Progress and Standardization. Proc. of the 7th Int. Conf. on Digital Audio Effects(DAFx'04), Naples, Italy, October5-8, 2004, pp. 157-162.
[51] ITU-R Recommend. BS. 1534-1. Method for the subjective Assessment of Intermediate Sound Quality Level of Coding Systems(MUSHRA). International Telecommunications Union, Geneva, Switzerland, 2001.
[52] Tsung Han Tsai, Chub Chu Yen. A High Quality Re-quantization/Quantization Method for MP3 and MPEG-4 AAC Audio Coding. IEEE International Symposium on Circuits and Systems, 2002, vol. 3, pp. 851-854.
[53] C. K. Seng, N. Tanaka, T. Nomura, O. Shimada, etc. Low Power Spectral Band Replication Technology for the MPEG-4 Audio Standard. ICICS-PCM, Singapore, December 2003.
[54] N. S. Jayant, J. D. Johnston, and R. Safranck. Signal Compression Based on Models of Human Perception. Proc. of the IEEE, October 1993, vol. 81, No. 10, pp. 1385-1422.
[55] J. Herre, C. Faller, S. Disch, and C. Ertel, etc. Spatial Audio Coding: Next-Generation Efficient and Compatible Coding of Multi-Channel Audio. AES 117th Convention, San Francisco, CA, USA, October 2004.
[56] Coding Technologies-http://www.codingtechnologies.com/.
[57] Fraunhofer IIS-http://www.iis.fraunhofer.de/amm/.
[58] 陈健．AAC：21世纪音频编码的主流．电声技术，2002．9．
[59] J. Herre, D. Schulz. Extending the MPEG-4 AAC Codec by Perceptual Noise Substitution. AES 104th Convention, Amsterdam, The Netherlands, May 1998.
[60] ITU-R Recommend. BS. 1116-1. Methods for the Subjective Assessment of Small Impairments in Audio Systems Including Multichannel Sound Systems. International Telecommunications Union, Geneva, Switzerland, 1994-1997.
[61] FAAC Home Page-http://www.audiocoding.com/.
[62] 胡瑞敏，艾浩军，张勇．数字音频压缩技术和AVS音频标准的研究．电视技术，2005．7．
[63] AVS-http://www.avs.org.cn/.
[2] 王炳锡．语音编码．西安电子科技大学出版社，2002．6．
[3] 张益贞，刘滔．Visual C++实现MPEG／JPEG编解码技术．人民邮电出版社，2002．
[4] ISO/IEC 11172-3. Information Technology-Coding of Moving Picture and Associated Audio for Digital Storage Media at up to About 1.5Mbit/s-part: 3. ISO/IEC JTC1/SC29 WG11, 1993
[5] ISO/IEC 13818-3. Information Technology-Generic Coding of Moving Picture and Associated Audio Information-Part 3: Audio. ISO/IEC JTC 1/SC29 WG11, 1998
[6] ISO/IEC 13818-7. Information Technology-Generic Coding of Moving Picture and Associated Audio Information-Part 7: Advanced Audio Coding(AAC). ISO/IEC JTC1/SC29 WG11, 1999.
[7] ISO/IEC 14496-3. Information Technology-Coding of Audio-Visual Objects-Part 3: Audio. ISO/IEC JTC1/SC29 WG11, 2001.
[8] ISO/IEC 14496-3: 2001/AMD1. Bandwidth Extension. ISO/IEC JTC1/SC29 WG11, 2003
[9] ISO/IEC 14496-3: 2001/AMD2. Parametric Audio Extension. ISO/IEC JTC1/SC29 WG11, 2004.
[10] 3GPP TS 26.401. Enhanced aacPlus general audio codec; General description. March 2005.
[11] 3GPP TS 26.402. Enhanced aacPlus general audio codec; Additional Decoder Tools. September 2005.
[12] 3GPP TS 26.403. Enhanced aacPlus general audio codec; Encoder Specification AAC Part. September 2004.
[13] 3GPP TS 26.404. Enhanced aacPlus general audio codec; Encoder Specification SBR Part. September 2004.
[14] 3GPP TS 26.405. Enhanced aacPlus general audio codec; Encoder Specification Parametric Stereo Part. March 2005.
[15] 李栋．MPEG-4音频编码标准 广播与电视技术，2001．12．
[16] 武银枝．基于DSP的MPE6-4 LD-AAC编码器的实现．西安电子科技大学硕士研究生学位论文，2005．1．
[17] 陈艳阳．MPEG-2AAC低复杂度双声道编解码器的DSP实现．东南大学硕士研究生学位论文，2001．3．
[18] 张艳．基于定点DSP的MPEG-4 AAC实时编解码系统研究．成都理工大学硕士研究生学位论文，2005．5．
[19] 汪斌．音频编解码算法及软硬件协同设计研究．浙江大学博士研究生学位论文，2004．5．
[20] 杨斌．AAC编码器的优化实现 西安交通大学硕士研究生学位论文，2003．3．
[21] 朱丽．心理声学模型算法改进．中国科学技术大学硕士学位论文，2003．5．
[22] 梁彬．时频技术及其在音频压缩编码中的应用．东南大学硕士研究生学位论文，2000．3．
[23] 徐盛．基于感知理论的低码率高质量音频编码．上海交通大学博士研究生学位论文，2000．6．
[24] 何兵．低码率感知音频编码研究．上海交通大学博士研究生学位论文，2002．2．
[25] 车振华．MPEG-2 AAC音频编码算法分析及其DSP实现．东南大学硕士研究生论文，2002．3．
[26] E. Schuijers, J. Breebaart, H. Purnhagen, and J. Engdegard. Low Complexity Parametric Stereo Coding. AES 116th Convention, Berlin, Germany, May 2004.
[27] H. Purnhagen. Low Complexity Parametric Stereo Coding in MPEG-4. Proc. of the 7th International Conference on Digital Audio Effects(DAFX-04), Naples, Italy, October 2004.
[28] M. Wolters, K. Kjorling, D. Homm, and H. Purnhagen. A Closer Look into MPEG-4 High Efficiency AAC. AES 115th Convention, New York, NY, USA, October 2003.
[29] M. Dietz, L. Liljeryd, K. Kjorling, and O. Kunz. Spectral Band Replication, A Novel Approach in Audio Coding. AES 112th Convention, Munich, Germany, May 2002.
[30] P. Ekstrand. Bandwidth Extension of Audio Signals by Spectral Band Replication. Proc. of the 1st IEEE Benelux Workshop on Model bansed Processing and Coding of Audio(MPCA-2002), Leuven, Belgium, November 2002, pp. 73-79.
[31] D. Frerichs. New MPEG-4 High-efficiency AAC Audio: Enabing New Applications. April 2003, download from http://www.mpegif.org.
[32] R. G.. v. d. Waal, R. N. J. Veldhuis. Subband coding of stereophonic digital audio signals. Proc. IEEE Int. Conf. on Acoustics, Speech, Signal Processing, Toronto, Ontario, Canada, April 1991.
[33] P. Duhamel, Y. Mahieux, and J. P. Petit. A fast algorithm for the implementation of filter banks based on "Time Domain Aliasing Cancellation". Proc. IEEE Int. Conf. on Acoustics, Speech, Signal Processing, 1991, vol. 3, pp. 2209-2212.
[34] T. Painter, A. Spanias. A Review of Algorithms for Perceptual Coding of Digital Audio Signals. Proc. of 13th Int. Conf. on Digital Signal Processing, July 1997, vol. 1, pp. 79-208.
[35] M. Dietz, S. Melzer. CT-aacplus-a State Of The Art Audio Coding Scheme. EBU Technical Review, No. 291, July 2002.
[36] A. Servetti, A. Rinotti, and J. C. D. Martin. Fast implementation of the MPEG-4 AAC main and low complexity decoder. Proc. of IEEE Int. Conf. on Acoustics, Speech, Signal Processing, 2004, pp. 249-252.
[37] I. Dimkovi, D. Milovanovi, Z. Bojkovi. Fast Software Implementation of MPEG Advanced Audio Encoder. 2002 14th Int. Conf. on Digital Signal Processing, vol. 2, pp. 839-843.
[38] E. Kurniawati, C. T. Lau, B. Premkumar. New Implementation Techniques of an Efficient MPEG Advanced Audio Coder. 2004 IEEE Transaction on Consumer Electronics, Vol: 50, No: 2.
[39] Y. Yakamizawa, T. Nomura, M. Ikekawa. High-Quality and Processor-Efficient Implementation of an MPEG-2 AAC Encoder. Proc. IEEE Int. Conf. on Acoustics, Speech, Signal Processing, 2001, Vol. 2, pp. 985-988.
[40] 岳玲，陈健，徐盛．MPEG-4AAC解码器在TMS320C6416上的实现．电声技术，2003．11．
[41] I. Dimkovic. Improved ISO AA C Coder.(from Internet)
[42] J. Herre, J. D. Johnston. Enhancing the Performance of Perceptual Audio Coders by Using Temporal Noise Shaping(TNS). AES 101 Convention, Los Angeles, 1996.
[43] J. Herre. Temporal Noise Shaping, Quantization and Coding Methods in Perceptual Audio Coding: A Tutorial Introduction. AES 17th Int. Conf. on High Quality Audio Coding, September 1999, pp 17-31.
[44] J. D. Johnston. Estimation of Perceptual Entropy Using Noise Masking Criteria. Proc. of IEEE Int. Conf. on Acoustics, Speech, and Signal Processing, 1998, pp. 2524-2527.
[45] A. D. Duefias, R. Pérez, B. Rivas, E. Alexandre, and A. S. Pena. A robust and efficient implementation of MPEG-2/4 AAC Natural Audio Coders. AES 112th Convention, Munich, Germany, May 2002.
[46] V. Prakash, A. Magadum. Optimal Fixed Point Implementation of MPEG-4 AAC Encoder. International Signal Processing Conference, Mar 31-Apr 3, 2003, Dallas, Texas, U. S. A.
[47] J. Engdegard, H. Purnhagen, J. Rodén, and L. Liljeryd. Synthetic Ambience in Parametric Stereo Coding. AES 116th Convention, Berlin, Germany, May 2004.
[48] J. Breebaart, S. v. d. Par, A. Kohlrausch, and E. Schuijers. Parametric Coding of Stereo Audio. EURASIP Journal on Applied Signal Processing 2005: 9, 1305-1322.
[49] J. Breebaart, S. v. d. Par, A. Kohlrausch, and E. Schuijers. High-quality Parametric Spatial Audio Coding at Low Bitrates. AES 116th Convention, Berlin, Germany, May 2004.
[50] J. Herre. From Joint Stereo to Spatial Audio Coding-Recent Progress and Standardization. Proc. of the 7th Int. Conf. on Digital Audio Effects(DAFx'04), Naples, Italy, October5-8, 2004, pp. 157-162.
[51] ITU-R Recommend. BS. 1534-1. Method for the subjective Assessment of Intermediate Sound Quality Level of Coding Systems(MUSHRA). International Telecommunications Union, Geneva, Switzerland, 2001.
[52] Tsung Han Tsai, Chub Chu Yen. A High Quality Re-quantization/Quantization Method for MP3 and MPEG-4 AAC Audio Coding. IEEE International Symposium on Circuits and Systems, 2002, vol. 3, pp. 851-854.
[53] C. K. Seng, N. Tanaka, T. Nomura, O. Shimada, etc. Low Power Spectral Band Replication Technology for the MPEG-4 Audio Standard. ICICS-PCM, Singapore, December 2003.
[54] N. S. Jayant, J. D. Johnston, and R. Safranck. Signal Compression Based on Models of Human Perception. Proc. of the IEEE, October 1993, vol. 81, No. 10, pp. 1385-1422.
[55] J. Herre, C. Faller, S. Disch, and C. Ertel, etc. Spatial Audio Coding: Next-Generation Efficient and Compatible Coding of Multi-Channel Audio. AES 117th Convention, San Francisco, CA, USA, October 2004.
[56] Coding Technologies-http://www.codingtechnologies.com/.
[57] Fraunhofer IIS-http://www.iis.fraunhofer.de/amm/.
[58] 陈健．AAC：21世纪音频编码的主流．电声技术，2002．9．
[59] J. Herre, D. Schulz. Extending the MPEG-4 AAC Codec by Perceptual Noise Substitution. AES 104th Convention, Amsterdam, The Netherlands, May 1998.
[60] ITU-R Recommend. BS. 1116-1. Methods for the Subjective Assessment of Small Impairments in Audio Systems Including Multichannel Sound Systems. International Telecommunications Union, Geneva, Switzerland, 1994-1997.
[61] FAAC Home Page-http://www.audiocoding.com/.
[62] 胡瑞敏，艾浩军，张勇．数字音频压缩技术和AVS音频标准的研究．电视技术，2005．7．
[63] AVS-http://www.avs.org.cn/.