基于DSP的EVRC声码器实现与优化
摘要
为了满足第三代移动通信系统对高质量语音和大容量系统的需要，在CDMA系统中普遍采用了变速率语音编码技术，根据话音的信号能量和背景噪声动态地决定编码速率，这种方法既保证了话音的质量，又降低了平均编码速率，从而增加了系统容量。
TIA于1997年正式推出IS-127标准，它是IS-95的可选语音服务标准(Service Option 3)和第三代移动通信系统CDMA2000的语音编解码标准，此标准的核心算法是增强型可变速率语音编码器(Enhanced Variable Rate Codec，简称EVRC)。EVRC声码器是可变速率的，最大编码速率为8kbps，在话音质量上接近于QCELP-13k的语音编码器，且具有更好的抗干扰能力。在目前的CDMA系统中，综合语音质量和编码速率，EVRC是最佳的语音编码器。
在IS-95和CDMA2000的基站中，EVRC声码器都得到了广泛的应用。由于我们开发的声码器主要用于基站，所以对性能的要求较高，选用了TI公司的最先进的DSP芯片TMS320C64xx。本文围绕定点EVRC声码器的软件优化，做了大量的工作，在充分理解TMS320C64xx CPU结构的基础上，针对语音信号处理中大量出现的循环运算进行了深度优化，大大提高了CPU的利用率以及CPU功能单元的并行程度，同时，我们还用TIA/EIA/IS-718的测试向量对定点EVRC声码器进行了严格比特对准测试，提高了声码器的鲁棒性。
最后，将我们开发的声码器与Delphi公司开发的声码器基准程序(Benchmark)作了比较，结果表明，我们的声码器的性能要明显高于Delphi公司的，这使得EVRC声码器具有较大的应用价值。
To meet the needs of the third mobile communication system for higher speech
quality and greater system capacity, the CDMA systems employ variable rate speech
coding technologies, which select the encode rate dynamically according to the signal
energy and background noise. This method insures the speech quality as well as reduces
,the average encode rate, so the system capacity is increased.
In 1997, TIA has released the standard of IS-127, it is Service option 3 of IS-95 and the voice encoder/decoder standard of the third mobile communication, the core algorithm of this standard is Enhanced Variable Rate Codec, the shortened form is EVRC. The EVRC Vocoder is Varialbe Rate, the maximal encode rate is Skbps, its voice quality is closed to QCELP-13k, and has better ability of anti-disturbance. At the present time, EVRC is the best vocoder in the CDMA system when take into account both the voice quality and the encode rate.
EVRC Vocoder is widely used in the Base Station of IS-95 and CDMA2000. Because our vocoder is mainly used in the Base Station, where the vocoder needs the excellent performance, so we select the TMS320C64xx , the most advanced DSPs of TI. The paper makes great efforts on the software optimization of EVRC vocoder. Based on the understanding of TMS320C64xx CPU structure, we do deeply-optimization on the loop which appear usually in voice signal processing, and this improve the utility ratio of CPU and the parallelity degree of CPU function cell. At the same time, we utilize the Bit-Exact test to test the fixed-point EVRC vocoder with the test vectors of TIA/EIA/IS-718, which improve the robustness of the vocoder.
At last, our vocoder is compared with the vocoder Benchmark of Delphi company, with the result that the performance of our vocoder is better than Delphi's obviously, thus make the vocoder has applied value.
TIA于1997年正式推出IS-127标准，它是IS-95的可选语音服务标准(Service Option 3)和第三代移动通信系统CDMA2000的语音编解码标准，此标准的核心算法是增强型可变速率语音编码器(Enhanced Variable Rate Codec，简称EVRC)。EVRC声码器是可变速率的，最大编码速率为8kbps，在话音质量上接近于QCELP-13k的语音编码器，且具有更好的抗干扰能力。在目前的CDMA系统中，综合语音质量和编码速率，EVRC是最佳的语音编码器。
在IS-95和CDMA2000的基站中，EVRC声码器都得到了广泛的应用。由于我们开发的声码器主要用于基站，所以对性能的要求较高，选用了TI公司的最先进的DSP芯片TMS320C64xx。本文围绕定点EVRC声码器的软件优化，做了大量的工作，在充分理解TMS320C64xx CPU结构的基础上，针对语音信号处理中大量出现的循环运算进行了深度优化，大大提高了CPU的利用率以及CPU功能单元的并行程度，同时，我们还用TIA/EIA/IS-718的测试向量对定点EVRC声码器进行了严格比特对准测试，提高了声码器的鲁棒性。
最后，将我们开发的声码器与Delphi公司开发的声码器基准程序(Benchmark)作了比较，结果表明，我们的声码器的性能要明显高于Delphi公司的，这使得EVRC声码器具有较大的应用价值。
To meet the needs of the third mobile communication system for higher speech
quality and greater system capacity, the CDMA systems employ variable rate speech
coding technologies, which select the encode rate dynamically according to the signal
energy and background noise. This method insures the speech quality as well as reduces
,the average encode rate, so the system capacity is increased.
In 1997, TIA has released the standard of IS-127, it is Service option 3 of IS-95 and the voice encoder/decoder standard of the third mobile communication, the core algorithm of this standard is Enhanced Variable Rate Codec, the shortened form is EVRC. The EVRC Vocoder is Varialbe Rate, the maximal encode rate is Skbps, its voice quality is closed to QCELP-13k, and has better ability of anti-disturbance. At the present time, EVRC is the best vocoder in the CDMA system when take into account both the voice quality and the encode rate.
EVRC Vocoder is widely used in the Base Station of IS-95 and CDMA2000. Because our vocoder is mainly used in the Base Station, where the vocoder needs the excellent performance, so we select the TMS320C64xx , the most advanced DSPs of TI. The paper makes great efforts on the software optimization of EVRC vocoder. Based on the understanding of TMS320C64xx CPU structure, we do deeply-optimization on the loop which appear usually in voice signal processing, and this improve the utility ratio of CPU and the parallelity degree of CPU function cell. At the same time, we utilize the Bit-Exact test to test the fixed-point EVRC vocoder with the test vectors of TIA/EIA/IS-718, which improve the robustness of the vocoder.
At last, our vocoder is compared with the vocoder Benchmark of Delphi company, with the result that the performance of our vocoder is better than Delphi's obviously, thus make the vocoder has applied value.
引文
[1] 丁琦，王炳锡，“EVRC语音编码算法的研究和实现”，信息工程大学学报，第4卷第3期，2003年9月。
[2] 董晖，姜秋喜，毕大平，“基于TMS320C6000高速算法的实现”，微处理机，2002年5月第二期
[3] 杨辉，秦品健，“浅谈TMS320C6000中断程序的实现方法“，信息技术，2002年第9期。
[4] 张莉莉，潘绍华，“16路语音压缩编解码的并行处理实现”，计算机工程，2002年8月第28卷第8期。
[5] 刘湘雯，张敏，赵世廉，“ITU—TG．728语音压缩算法的实时实现”，空军工程大学学报(自然科学版)，2002年4月第三卷第2期。
[6] 王尚武，“语音压缩中的线性预测编码技术“，微机发展，2002年第6期。
[7] TIA/EIA/IS-127: Enhanced Varialbe Rate Codec, Speech Service Option 3 for Wideband Spread Spectrum Digital Systems, September 1996
[8] TIA/EIA/IS-718: Minimum Performance Specification for the Enhanced Varible Rate Codec,Speech Service Option 3 for Spread Spectrum Digital Systems, 1998.7
[9] DCSC64xSUM-053012: TMS320C64X Performance Specifications(Summary), Delphi Communications Systems,Inc, 2002
[10] TI, Code Composer Studio Getting Started Guide,SPRU509C, November 2001
[11] TI, TMS320C6000 Assembly Language Tools User's Guide, SPRU186K, October 2002
[12] TI, TMS320 DSP/BIOS User's Guide, SPRU 423, November 2002
[13] TI, TMS320C6000 Assembly Language Tools User's Guide, SPRU186, October 2002
[14] TI, TMS320C6000 DSP/BIOS Application Programming Interface (API), SPRU403, October 2002
[15] TI, TMS320C6000 Chip Support Library API Reference Guide, SPRU401, December 2002
[16] TI, TMS320C6000 Optimizing Compiler User's Guide, SPRU 187K, October 2002
[17] TI, TMS320C6000 Programmer's Guide, SPRU198G, August 2002
[18] TI, TMS320C6000 CPU and Instruction Set Reference Guide, SPRU189F, October 2000
[19] TI, TMS320C6000 Peripherals Reference Guide, SPRU190D, February 2001
[20] TI, TMS320C64x Technical Overview, SPRU395B, Janrary 2001
[21] TI, C6416 Test and Evaluation Board Quick Start Guide, SPRU561, October 2001
[22] TI, TMS320C6414、TMS320C6415、TMS320C6416 Fixed-Point Digital Signal Processors, SPRS146H, February2001
[23] R.Salami, C.Laflamme, D.Massaloux, "A toll quality 8Kb/s speech codec for the personal communications system(PCS)" , IEEE Trans.Veh.Technol.,vol.43, No.3, pp.808-816,Aug. 1994.
[24] Qualcomm Inc, "High rate speech service option for wideband spread spectrum communications systems" ,Feb, 1995
[25] Ahmed J.Jameel,YouXiaohu,GaoXiqi, "Joint Source Channel Decoding of EVRC Speech Encoder Using Residual Redundancy" ,Journal.of Southeast University(English Edition),June 2002,Vol. 18,No.2
[26] Alan V．Oppenheim，Ronald W．Schafer，John R．Buck，刘树棠，黄建国译，《离散时间信号处理(第2版)》，西安：西安交通大学出版社，2001．9。
[27] 赵力，《语音信号处理》，北京：机械工业出版社，2003．4
[28] 姚天任，《数字语音处理》，武汉：华中理工大学出版社，1992．4
[29] 王炳锡，《语音编码》，西安：西安电子科技大学出版社，2002．7
[30] 胡广书，《数字信号处理-理论、算法与实现》，北京：清华大学出版社，1997．8
[31] 易克初，田斌，富强，《语音信号处理》。北京：国防工业出版社，2001
[32] 杨行峻，迟惠生等，《语音信号数字处理》，北京：电子工业出版社，1995．8
[33] 曾兴文，刘乃安，《通信中的扩展频谱技术》，西安：西安电子科技大学出版社，1999．11
[34] 李方慧，王飞，何佩琨，《TMS320C6000系列DSPs原理与应用(第二版)》北京：电子工业出版社，2003．1
[35] 彭启琮，李玉柏，管庆编，《DSP技术的发展与应用》，北京：高等教育出版社，2002．9
[36] 张雄伟，陈亮，徐光辉，《DSP芯片的原理与开发应用(第三版)》，北京：电子工业出版社，2003．2
[2] 董晖，姜秋喜，毕大平，“基于TMS320C6000高速算法的实现”，微处理机，2002年5月第二期
[3] 杨辉，秦品健，“浅谈TMS320C6000中断程序的实现方法“，信息技术，2002年第9期。
[4] 张莉莉，潘绍华，“16路语音压缩编解码的并行处理实现”，计算机工程，2002年8月第28卷第8期。
[5] 刘湘雯，张敏，赵世廉，“ITU—TG．728语音压缩算法的实时实现”，空军工程大学学报(自然科学版)，2002年4月第三卷第2期。
[6] 王尚武，“语音压缩中的线性预测编码技术“，微机发展，2002年第6期。
[7] TIA/EIA/IS-127: Enhanced Varialbe Rate Codec, Speech Service Option 3 for Wideband Spread Spectrum Digital Systems, September 1996
[8] TIA/EIA/IS-718: Minimum Performance Specification for the Enhanced Varible Rate Codec,Speech Service Option 3 for Spread Spectrum Digital Systems, 1998.7
[9] DCSC64xSUM-053012: TMS320C64X Performance Specifications(Summary), Delphi Communications Systems,Inc, 2002
[10] TI, Code Composer Studio Getting Started Guide,SPRU509C, November 2001
[11] TI, TMS320C6000 Assembly Language Tools User's Guide, SPRU186K, October 2002
[12] TI, TMS320 DSP/BIOS User's Guide, SPRU 423, November 2002
[13] TI, TMS320C6000 Assembly Language Tools User's Guide, SPRU186, October 2002
[14] TI, TMS320C6000 DSP/BIOS Application Programming Interface (API), SPRU403, October 2002
[15] TI, TMS320C6000 Chip Support Library API Reference Guide, SPRU401, December 2002
[16] TI, TMS320C6000 Optimizing Compiler User's Guide, SPRU 187K, October 2002
[17] TI, TMS320C6000 Programmer's Guide, SPRU198G, August 2002
[18] TI, TMS320C6000 CPU and Instruction Set Reference Guide, SPRU189F, October 2000
[19] TI, TMS320C6000 Peripherals Reference Guide, SPRU190D, February 2001
[20] TI, TMS320C64x Technical Overview, SPRU395B, Janrary 2001
[21] TI, C6416 Test and Evaluation Board Quick Start Guide, SPRU561, October 2001
[22] TI, TMS320C6414、TMS320C6415、TMS320C6416 Fixed-Point Digital Signal Processors, SPRS146H, February2001
[23] R.Salami, C.Laflamme, D.Massaloux, "A toll quality 8Kb/s speech codec for the personal communications system(PCS)" , IEEE Trans.Veh.Technol.,vol.43, No.3, pp.808-816,Aug. 1994.
[24] Qualcomm Inc, "High rate speech service option for wideband spread spectrum communications systems" ,Feb, 1995
[25] Ahmed J.Jameel,YouXiaohu,GaoXiqi, "Joint Source Channel Decoding of EVRC Speech Encoder Using Residual Redundancy" ,Journal.of Southeast University(English Edition),June 2002,Vol. 18,No.2
[26] Alan V．Oppenheim，Ronald W．Schafer，John R．Buck，刘树棠，黄建国译，《离散时间信号处理(第2版)》，西安：西安交通大学出版社，2001．9。
[27] 赵力，《语音信号处理》，北京：机械工业出版社，2003．4
[28] 姚天任，《数字语音处理》，武汉：华中理工大学出版社，1992．4
[29] 王炳锡，《语音编码》，西安：西安电子科技大学出版社，2002．7
[30] 胡广书，《数字信号处理-理论、算法与实现》，北京：清华大学出版社，1997．8
[31] 易克初，田斌，富强，《语音信号处理》。北京：国防工业出版社，2001
[32] 杨行峻，迟惠生等，《语音信号数字处理》，北京：电子工业出版社，1995．8
[33] 曾兴文，刘乃安，《通信中的扩展频谱技术》，西安：西安电子科技大学出版社，1999．11
[34] 李方慧，王飞，何佩琨，《TMS320C6000系列DSPs原理与应用(第二版)》北京：电子工业出版社，2003．1
[35] 彭启琮，李玉柏，管庆编，《DSP技术的发展与应用》，北京：高等教育出版社，2002．9
[36] 张雄伟，陈亮，徐光辉，《DSP芯片的原理与开发应用(第三版)》，北京：电子工业出版社，2003．2