基于Android平台的均衡器算法研究
摘要
随着数字信号处理技术与芯片的发展,数字音效处理技术在人们的生活中随处可见。同时,伴随着3G的发展,手机终端也高速发展,数字音效处理技术在手机上应用成为可能。Android操作系统是Google推出的一款专为移动平台定制的操作系统,该系统已经成门智能手机中最热门的操作系统,关于Android的开发也越来越多。随着人们对音乐品味的提高,人们对手机的要求也越来越高,在Android上进行音效处理开发成为一种必要。
本文在介绍Android操作系统的发展与开发平台的基础上,进行了数字音效的研究,重点研究了均衡器的算法。对现有方法进行分析对比,根据手机平台的需要选择计算量较小的IIR滤波器进行均衡器设计,采用双线性变换法将模拟滤波器变换到数字域。此方法虽然计算简单,但是存在着高频频率畸变、均衡器增益不准确的缺点。本文分析了增益不准确的原因,减少相邻频段的干扰,提高均衡器准确性。
最后,本文将改进后的方法在Android平台实现,测试结果表明算法能够在手机平台运行,且均衡效果理想。
With the development of digital signal processing technology and chips, digital audio effect processing technology has been used in everywhere of people's lives. Meanwhile, with the development of 3G, mobile terminals have developed with high speed, it is possible to use digital sound processing technology in the mobile phone applications. Android is the most popular smart phone operating system, along with the improvement of people's musical tastes, audio processing on Android is necessary.
This paper describes the development of the Android operating system and platform, researches digital audio effect algorithm, especially the equalizer algorithm. Base on analysis and comparison of existing methods, according to the needs of mobile platform, the IIR filter design method is selected. The analog filter is transformed to the digital domain with bilinear transformation. The calculation is simple, but there is distortion at high frequency, and the equalizer gain is inaccurate. This paper analyzes the reasons for the inaccurate gain, reduce the adjacent band interference and improve the accuracy of the equalizer.
At last, this method is realized on the Android platform. The test results show that the algorithm can run in the mobile platform, and the results of the results are satisfactory.
本文在介绍Android操作系统的发展与开发平台的基础上,进行了数字音效的研究,重点研究了均衡器的算法。对现有方法进行分析对比,根据手机平台的需要选择计算量较小的IIR滤波器进行均衡器设计,采用双线性变换法将模拟滤波器变换到数字域。此方法虽然计算简单,但是存在着高频频率畸变、均衡器增益不准确的缺点。本文分析了增益不准确的原因,减少相邻频段的干扰,提高均衡器准确性。
最后,本文将改进后的方法在Android平台实现,测试结果表明算法能够在手机平台运行,且均衡效果理想。
With the development of digital signal processing technology and chips, digital audio effect processing technology has been used in everywhere of people's lives. Meanwhile, with the development of 3G, mobile terminals have developed with high speed, it is possible to use digital sound processing technology in the mobile phone applications. Android is the most popular smart phone operating system, along with the improvement of people's musical tastes, audio processing on Android is necessary.
This paper describes the development of the Android operating system and platform, researches digital audio effect algorithm, especially the equalizer algorithm. Base on analysis and comparison of existing methods, according to the needs of mobile platform, the IIR filter design method is selected. The analog filter is transformed to the digital domain with bilinear transformation. The calculation is simple, but there is distortion at high frequency, and the equalizer gain is inaccurate. This paper analyzes the reasons for the inaccurate gain, reduce the adjacent band interference and improve the accuracy of the equalizer.
At last, this method is realized on the Android platform. The test results show that the algorithm can run in the mobile platform, and the results of the results are satisfactory.
引文
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[5]M. R. Schroeder. Digital simulation of sound transmission in reverberant spaces [J]. J. Acoust. Soc. Am,1970,47(2):424-431.
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[29]王喜明.数字音频设备的研究与实现[D].大连：大连理工大学,2010.
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[32]Toon van Waterschoot, Marc Moonen. A pole-zero placement technique for designing second-order IIR parametric equalizer filters[C]. IEEE Transactions On Audio, Speech, And Language Processing, Leuven, Leuven, November 2007,15(8):2561-2565.
[33]Joshua D. Reiss. Design of audio parametric equalizer filters directly in the digital domain[J]. IEEE Transactions On Audio, Speech, And Language Processing, London, UK, August 2011,19(6):1843-1848.
[34]R. Bristow-Johnson. Audio EQ Cookbook[EB/OL]. http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt.
[35]Android developers. Installing the SDK[EB/OL]. http://developer.android.com/sdk/installing.html.
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[2]张磊.数字效果器的研究与实现[D].大连：大连理工大学,2010.
[3]R. Bristow-Johnson. The equivalence of various methods of computing biquad coefficients for audio parametric equalizers[C]. The 97th Convention of the AES, San Francisco, November 1994, AES Preprint 3906.
[4]S. J. Orfanidis. Digital parametric equalizer design with prescribed Nyquist-frequency gain[J].J. Aud. Eng. Soc,1997,45(6):444-455.
[5]M. R. Schroeder. Digital simulation of sound transmission in reverberant spaces [J]. J. Acoust. Soc. Am,1970,47(2):424-431.
[6]Moorer A. James. About this reverberation business [J]. Computer Music Journal.1979, 3(2):13-28.
[7]周婧洁,陈建平,吉晓东.几种数字混响器模型的比较与分析[J].南通大学学报,2010,6(9)：23-28.
[8]井洪亮.基于Android的H.264/AVC解码器的设计与实现[D].哈尔滨：哈尔滨工业大学,2010.
[9]Google. Google Projects for Android[EB/OL]. http://code.google.com/android/.
[10]中国信息产业网Android成最受欢迎智能手机平台平板电脑占据22%[EB/OL].http://www.cnii.com.cn/index/content/2011-02/09/content_836876.htm.
[11]Wikipedia. Android(operating system)[EB/OL]. http://en.wikipedia.org/wiki/Android_(operating_system).
[12]吕娜Android之父Andy Rubin:生而Geek[J]程序员,2010,9：7.
[13]Open Handset Alliance members page[EB/OL]. http://www.openhandsetalliance.com.
[14]E2ECloud工作室.深入浅出Google Android[M]北京：人民邮电出版社,2009.
[15]eoeAndroid开发者社区Google Android创赢路线与产品开发实战[M].北京：电子工业出版社,2010.
[16]Ed Burnette著,张波,高朝勤,杨越等译Android基础教程[M].北京：人民邮电出版社,2009.
[17]肖金秀.多媒体技术及应用[M].北京：冶金工业出版社,2006.
[18]鲁宏伟,汪厚祥.多媒体计算机技术(第2版)[M].北京：电子工业出版社,2004.
[19]张绍高,数字声频技术原理及应用[M].北京：国防工业出版社,2000.
[20]樊昌信,张甫翊,徐炳祥,等.通信原理(第5版)[M].北京：国防工业出版社,2001.
[21]craig@ccrma.stanford.edu. WAVE PCM soundfile format[EB/OL]. https://ccrma.stanford.edu/courses/422/projects/WaveFormat/.
[22]胡广书.数字信号处理(第二版)[M].北京：清华大学出版社,2003.
[23]程佩青.数字信号处理教程[M].北京：清华大学出版社,2001.
[24]卢官明,宗昉.数字音频原理及应用[M].北京：机械工业出版社,2005.
[25]宗志毅.高效窄带FIR滤波器的设计与研究[D].哈尔滨：哈尔滨工程大学,2003.
[26]Dennis A. Bohn. Constant-Q graphic equalizers[J]. J. Audio Eng Soc, September 1986, 34(9):611-626.
[27]R. A. Greiner, M. Schoessow. Design aspects of graphic equalizers[J]. J. Audio Eng. Soc,1983,31(6):394-407.
[28]王天宝.数字调音系统的研究与实现[D].大连：大连理工大学,2010.
[29]王喜明.数字音频设备的研究与实现[D].大连：大连理工大学,2010.
[30]Udo Zolzer. Digital Audio Signal Processing[M]. New York:John Wiley & Sons,1998
[31]Lucian Stanch, Leonard Banu. Digital parametric equalizers for high quality audio signals[C]. IEEE International Symposium on Signals, Circuits and Systems, Bucharest, Romania,14-15 July 2005,2:573-576.
[32]Toon van Waterschoot, Marc Moonen. A pole-zero placement technique for designing second-order IIR parametric equalizer filters[C]. IEEE Transactions On Audio, Speech, And Language Processing, Leuven, Leuven, November 2007,15(8):2561-2565.
[33]Joshua D. Reiss. Design of audio parametric equalizer filters directly in the digital domain[J]. IEEE Transactions On Audio, Speech, And Language Processing, London, UK, August 2011,19(6):1843-1848.
[34]R. Bristow-Johnson. Audio EQ Cookbook[EB/OL]. http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt.
[35]Android developers. Installing the SDK[EB/OL]. http://developer.android.com/sdk/installing.html.
[36]Dmitry Vaguine. JEQ-Java Stereo Equalizer[CP/OL]. http://jeq.sourceforge.net.
[37]Android developers. AudioTrack[EB/OL]. http://developer.android.com/reference/android/media/AudioTrack.html.