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研究生:池勇輝
研究生(外文):Yong-Huei Chih
論文名稱:語音封包遺失之錯誤傳播長度測量與即時通訊效應研究
論文名稱(外文):Measurement of Error Propagation Length from Speech Packet Loss and Studies of Its Real-time Communications Effects
指導教授:賴文彬賴文彬引用關係
學位類別:碩士
校院名稱:元智大學
系所名稱:通訊工程學系
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2009
畢業學年度:97
語文別:中文
論文頁數:44
中文關鍵詞:語音編碼錯誤傳播封包遺失補償網路電話
外文關鍵詞:Speech CodecError PropagationPacket Loss ConcealmentVoIP
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語音封包遺失是損傷VoIP即時通訊品質的重要因素。語音封包遺失損傷中,包含「不完美的封包遺失補償(PLC)」與後續的「錯誤傳播(EP)」效應。其中,EP會影響判斷封包重要性的準確度,必須延遲發送時間,才能考量錯誤傳播效應,以提昇即時封包重要性的準確度。
本研究旨在探討VoIP封包重要性的準確度與通訊的即時性之間取捨的問題。在通話的當下,為了提昇封包重要性的準確度,可刻意延遲發送時間,藉以參考後續音框之錯誤傳播效應;然而,此延遲將受到VoIP即時性的限制,謂之兩難。本研究以離線的方式探討中低位元率語音編碼器之錯誤傳播效應,提出一個能解決「最小化額外編碼延遲」與「最大化即時封包重要性的準確度」此兩難問題之最佳化策略。對於VoIP即時通訊而言,語音封包如能正確地被分類,再透過差異性服務網路傳輸,對較重要的封包給予較多的網路資源,將可提昇VoIP之整體通話品質。
Packet loss is the most important quality degradation factor of real-time Voice over IP (VoIP) communications. This factor consists of two effects: Imperfect Packet Loss Concealment (IPLC) and IPLC associated Error Propagation (EP), where ignoring the latter will affect the accuracy of real-time VoIP packet importance. Thus, it is necessary to include the EP effect to enhance the accuracy of real-time packet importance with the cost of an extra encoding delay.
This research studies the dilemma between the accuracy of packet importance and the realtime of communications. At the moment of conversation, an intentional delay for a speech frame to account for its EP effect can help to enhance the accuracy of packet importance; however, such a delay will be limited by the real-time requirement of VoIP, thus it becomes the dilemma mentioned above. To solve this problem, we first studied the EP effects of median and low-bit rate speech codecs using an off-line method, and then proposed an optimal strategy to balance between the demands of minimizing the extra encoding delay and maximizing the accuracy of real-time packet importance. For real-time VoIP communications, the integral VoIP quality can be greatly enhanced on a differentiated service network if proper network resources are reserved for VoIP packets accurately according to their real-time packet importance.
1 緒論 1
1.1 研究目標 1
1.2 研究動機 2
1.3 本研究之貢獻 5
1.4 論文架構 5
2 研究背景與文獻探討 6
2.1 語音品質的測量 6
2.2 語音編碼器簡介 8
2.3 語音封包分類傳輸的需求 11
2.4 VOIP單封包遺失之損傷效應 14
2.5 VOIP封包重要性之計算 15
2.6 本研究之定位 16
3 研究方法 17
3.1 非感知測量 18
3.1.1 Test1: 語音編碼器的錯誤傳播長度測量的方法 19
3.2 感知測量 20
3.2.1 Test2: 單封包遺失整體損傷及計算封包重要性的方法 20
3.2.2 Test3: 測量封包遺失補償與錯誤傳播佔整體損傷比例的方法 22
3.2.3 Test4: 測量錯誤傳播效應影響即時計算封包重要性準確度的方法 26
4 結果與分析 28
4.1 非感知方法之各種語音編碼器錯誤傳播長度的測量結果 29
4.2 語音封包重要性與單封包遺失損傷的計算結果與分析 31
4.3 封包遺失補償與錯誤傳播之損傷比例 33
4.4 測量錯誤傳播效應影響即時封包重要性準確度的結果 35
4.5 即時封包重要性預測的最佳化策略 36
5 結論 41
5.1 討論 41
5.2 未來展望 42
6 參考文獻 43
[1]U. Black, Voice over IP, 2nd ed., Prentice Hall Internal, Jan. 2002.
[2]K. Maheswari and M. Punithavalli, “A Survey of Packet Loss in VoIP,” International Journal of Computational Intelligence Research, vol 5, pp. 57-66, 2009.
[3]IETF RFC 3393, IP Packet Delay Variation Metric for IP Performance Metrics (IPPM), Nov. 2002.
[4]3G TS 26.091 V5.0.0 (2002–06), AMR Speech Codec: Error Concealment of Lost Frames (Release 5) 3GPP, 2002.
[5]K. Clüver and P. Noll, “Reconstruction of missing speech frames using sub-band excitation,” in IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis, Jun. 1996.
[6]J. D. Rosenberg, “G.729 Error Recovery for Internet Telephony,” Bell Laboratories & Columbia University report, spring 1997.
[7]ITU-T Recommendation G.723.1, Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s, May 2003.
[8]ITU-T Recommendation G.729, Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction (CS-ACELP), Mar. 1996.
[9]3G TS 26.090 V5.0.0 (2002-06), AMR Speech Codec: Transcoding Functions (Release 5) 3GPP, 2002.
[10]S. Andersen and A. Duric, “Internet Los Bit Rate Codec (iLBC),” IETF RFC 3951, Dec. 2004.
[11]ITU-T Recommendation G.107, The E-model: a computational model for use in transmission planning, Aug. 2008.
[12]ITU-T Recommendation G.114, One-way transmission time, May 2006.
[13]M. Marchese, QoS Over Heterogeneous Networks, John Wiley, June 2007.
[14]ITU-T Recommendation P.800, Methods for subjective determination of transmission quality, ITU-T Std., Aug. 1996.
[15]ITU-T Recommendation P.862, Perceptual evaluation of speech quality (PESQ): An objective method for end-to-end speech quality assessment of narrow-band telephone networks and speech codecs, Feb. 2001.
[16]ITU-T Recommendation G.711, Pules Code Modulation (PCM) of voice frequencies, November 1988.
[17]TU-T Recommendation G.721, 32 kbit/s adaptive differential pulse code modulation (ADPCM), Nov. 1988.
[18]TU-T Recommendation G.726, 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM), Dec. 2009.
[19]LPC-10 speech coder software, [Online]. Available: http://www.arl.wustl.edu/~jaf/lpc/
[20]B. E. Carpenter and K. Nichols, “Differentiated service in the internet,” Proceedings of the IEEE, vol. 90, no. 9, September 2002, pp. 1479-1494.
[21]D. W. Petr, L. A. DaSilva and V. S. Frost, “Priority discarding of speech in integrated packet networks,” IEEE Journal on Selected Areas in Communications, vol. 7, no. 5, pp. 644–656, 1989.
[22]J. C. De Martin, “Source-driven packet marking for speech transmission over differentiated-services networks,” in Proceedings of the IEEE International Conference on Audio, Speech and Signal Processing, Salt Lake City, UT, May 2001, pp. 753–756.
[23]M. Petracca, A. Servetti, and J. C. De Martin, “Voice transmission over 802.11 wireless networks using analysis-by-synthesis packet classification,” in First International Symposium on Control, Communications and Signal Processing, Hammamet, Tunesia, Mar. 2004, pp. 587–590.
[24]C. Hoene, I. Marsh, G. Schäfer and A. Wolisz, “Error Propagation After Concealing a Lost Speech Frame,” Workshop on Multimedia Communication: State of the Art and Future Directions, IEEE International Conference on Communications (ICC''06), 11-15 June 2006, Istanbul, Turkey.
[25]C. Hoene, B. Rathke, and A. Wolisz, “On the importance of a VoIP packet,” Proceedings of ISCA Tutorial and Research Workshop on the Auditory Quality of Systems, Mont-Cenis, Germany, Apr. 2003.
[26]ITU-T Recommendation P.Sup23, ITU-T coded-speech database, Feb. 1998.
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