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| Title: | 大型網路語音會談中回音消除方法
Echo Cancellation In Large-Scale VoIP Conferencing |
| Authors: | 祁立誠
Chi, Li-Chen |
| Contributors: | 連耀南
Lien, Yao-Nan
祁立誠
Chi, Li-Chen |
| Keywords: | 回音消除
網路語音會談
語音動態偵測
echo cancellation
VoIP
VAD |
| Date: | 2009 |
| Issue Date: | 2010-04-09 13:24:02 (UTC+8) |
| Abstract: | 隨著網路技術的發展，目前網路電話(VoIP)已有逐漸取代傳統電話的趨勢。尤其能夠允許多人同時在線上進行會談是其最大的優勢之一。但在多人參與網路會談時，因為聲音在空間中傳遞或反射等因素，使得由喇叭發出的聲音再次被麥克風收回，造成回音的產生。會談中只要有一位使用者的裝置發生回音時，回音訊號就會在與會者之間擴散，使得所有使用者均會受到影響，進而嚴重影響網路通話的進行。此狀況在參與會談人數越多時，發生機率越高，且對通話品質影響越嚴重。
傳統電話在一對一通話時，通常使用遠端回音消除機制(Near End Echo Canceller)，由接收端在接收聲音後先暫存在記憶體中再播放，再將麥克風擷取的聲音與事先暫存的訊號反向後混合，以抵銷回音。網路會談的環境下，由於沒有標準的聽筒設備，使得回音發生的時間難以預估。且多人參與的網路會談中，由於收聽者所聽到的聲音可能混合多個使用者說話的聲音與回音，使得回音訊號難以偵測。另外，由於網路傳輸的特性，回音訊號到達的時間與順序都難以預估，這使得回音消除機制在多人網路回談中經常失效。
本研究提出藉由語音動態偵測(Voice Activity Detection-VAD)的方式分辨回音訊號，藉由本研究所提出的語音能量VAD判定機制，能夠有效區別正常語音與回音的差異，即可有效的消除回音，同時發揮靜音抑制（Slience Suppression）的效果，阻擋不含語音內容的封包，降低網路頻寬耗用。本研究以自行開發的VoIP軟體進行實地測試實驗，實驗中顯示，我們的方法能消除85%以上的回音。
With the prosperous development of Internet technology, traditional phone service is being replaced gradually byVoice-over-IP (VoIP) technology. One of the critical problem that is yet to be improved is the echo problem. Due to the difference in working environment, conventional echo cancellation technology may not work well on VoIP system. The echo problem is becoming more critical as the number of participants in a talk session increases. As long as one user fails to depress echos, every other participant in the conference will be infected. The more participant, the higher probability of echo infection.
We propose an energy based Voice Activity Detection (VAD) mechnism that effectively differentiate echo from speech signal. Our VAD algrouthm records a user’s speech volume, and based on this information to determine whether the frame is echo or not. By applying this mechnism to network conference, we can filter out echo frames and suppress slience at same time to save bandwidth consumption. We experimented on a self-developed VoIP software platform, the experiment result shows that our method can eliminate more than 85% of the echo. |
| Reference: | [1] U.I. Choudhry, JongWon Kim, and Hong Kook Kim, "A Highly Adaptive Acoustic Echo Cancellation Solution for VoIP Conferencing Systems", IEEE International Conference on Computer Systems and Applications, 2006, pp. 433-436.
[2] G. S. Fang, "Voice Channel Echo Cancellation", IEEE Communications Magazine, Vol. 21, Issue 9, Dec. 1983, pp.11-14.
[3] Xiaohui Gu, Zhen Wen, Philip S. Yu, and Zon-Yin Shae, "peerTalk: A Peer-to-Peer Multi-Party Voice-Over-IP System", Parallel and Distributed Systems, IEEE Trans. on Publication, Vol. 19, No. 4, April 2008.
[4] Perry P. He, Roman A. Dyba, and Lucio F.C. Pessoa, "Network Echo Cancellers: Requirements, Applications and Solutions", AnalogZONE, 2004.
[5] Brant M. Helf, "Far end echo cancellation method and apparatus”, U.S. Patent 4,995,030, Feb. 19, 1991.
[6] M. Hiraguchi, "Full duplex modem having two echo cancellers for a near end echo and a far end echo", U.S. Patent 4,935,919, 19 Jun. 19, 1990.
[7] Yao-Nan Lien, Li-Cheng Chi and Yuh-Sheng Shaw, "A Walkie-Talkie-Like Emergency Communication System for Catastrophic Natural Disasters", Proc. of 10th International Symposium on Pervasive Systems, Algorithms and Networks (ISPAN09), Dec. 14-16, 2009.
[8] P. Marques, F. Sousa, and J. Leitao, "A DSP Based Long Distance Echo Canceller using Short Length Centered Adaptive Filters", Proc. of ICASSP, 1997.
[9] B. S. Nollet, and D. L. Jones, "Nonlinear Echo Cancellation For Hands-Free Speakerphones", Proc. of NSIP`97, Michigan USA, Sep. 1997.
[10] K. Ochiai, T. Araseki, and T. Ogihara, "Echo canceller with two echo path models", IEEE Trans. on Commun., Vol. COM-25, No. 6, June 1977, pp. 589-595.
[11] G. Periakarruppan, and H. A. Abdul-Rashid, "Packet based echo cancellation for VoIP networks", Computers and Electrical Engineering, Vol. 33, No. 2, 2007, pp. 139-148.
[12] Petr Pollak, Pavel Sovka, and Jan Uhlir, "Noise Sup-pression System for a Car", Proc. of the Third European Conference on Speech, Communication and Technology -EUROSPEECH`93, Berlin, Sep. 1993, pp. 1073-1076.
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[14] R. V. Prasad, R. Muralishhankar, S. Vijay, H. N. Shankar, P. Pawelczak, and I. Miemegeers, “Voice activity detection for VoIP-an information theoretic approach”, Proc. of IEEE Global Telecommunications Conference, 2006, pp. 1-6.
[15] I. Rassameeroj, and S. Tangwongsan, "Echo Cancellation in Voice over IP", Proc of 5th International Conference on Information Technology and Applications (ICITA), 2008, pp. 570-575.
[16] P. Renevey, and A. Drygajlo, “Entropy based voice activity detection in very noisy conditions”, Proc. of European Conference on Speech Communication and Technology (ISCA EUROSPEECH ’01), Sep. 2001, pp. 1887-1890.
[17] B. Widrow, and M. E. Hoff, "Adaptive switching circuits", IRE WESCON Convention Record part 4, 1960, pp. 96-104.
[18] B. Widrow, and SD Stearns, “Adaptive Signal Processing”, Prentice-Hall, Nglewood Cliffs, NJ, 1985.
[19] Echo cancellation, http://en.wikipedia.org/wiki/Echo_cancellation, Retrieved at November 11, 2009.
[20]Echo suppressor, http://en.wikipedia.org/wiki/Echo_suppressor, Retrieved at November 11, 2009.
[21] Mean Opinion Score, http://en.wikipedia.org/wiki/Mean_Opinion_Score, Retrieved at July 09, 2009. |
| Description: | 碩士
國立政治大學
資訊科學學系
96753013
98 |
| Source URI: | http://thesis.lib.nccu.edu.tw/record/#G0096753013 |
| Data Type: | thesis |
| Appears in Collections: | [資訊科學系] 學位論文
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