一種可用于CDMA移動通信的變速率語音編碼算法
A variable rate speech coding algorithm for CDMA mobile communications
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摘要: 該文提出了一種碼率為 0.75-5.4kb/s可變速率的高質(zhì)量語音編碼講法。該算法對CELP的激勵進行了改進,根據(jù)語音的特征把語音分成4類,不同類型的語音采用不同的激勵碼本。特別是對于濁音,提出了一種基于基音同步的嵌入分裂式激勵碼本,該碼本利用濁音具有準周期性的特點,使該算法在很低的碼率下就可很好地恢復(fù)濁音信號,克服了CELP在4kb/s速率以下因碼本尺寸小而導(dǎo)致合成語音質(zhì)量差的缺點。經(jīng)非正式聽音測試,它的主觀質(zhì)量超過了1～8kb/s的可變速率QCELP系統(tǒng),并且平均速率大約只有2kb/s,比QCELP的5kb/s平均速率低了很多、非常適用于 CDMA移動通信系統(tǒng)。
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關(guān)鍵詞:
- 語音編碼; 變速率; 矢量量化; 基音周期
Abstract: This paper focuses on the design of high quality speech coding with variable rate at 0.75～5.4kb/s. The new algorithm classifies input speech signals as noise, unvoiced speech, transitional speech and voiced speech, and it uses different codebooks as excited impulses according to different types of speech frames. Especially, an embedded splitting vector quantization method based on pitch synchronization to synthesize voiced speech is proposed. The speech can be recovered very well at low bit rate by making use of the itch periodicity for voiced speech frames. This new algorithm can overcome the disadvantage of CELP whose recovered speech quality will degrade quickly when the bit rate is below 4kb/s because the codebook size is too small. the informal listeing test results show that the subject quality of the algorithm exceeds that of QCELP while the average bit rate of the algorithm is only about 2kb/s, which is much lower than that of QCELP whose average bit rate is about 5kb/s. This new speech coding algorithm is therefore very apt to CDMA mobile communication systems. -
A.S. Spanias, Speech coding: A tutorial review, Proc. IEEE, 1994, 82(10), 1541-1582.[2]W. B. Kleijn, K. K. Paliwal, Speech Coding and Synthesis, Amsterdam, The Netherlands: Elsevier, 1995, 15-40.[3]R.V. Cox, Three new speech coders from the ITU cover a rang of application. IEEE Comm.Mag., 1997, 35(9), 40-47.[4]K. Kondo, M. Ohno, Variable rate embedded ADPCM coding scheme for packet speech on ATMnetworks. Proc. of ICASSP, New Mexico, USA, 1990, 405. 3.1-405. 3.4.[5]Speech service option standard for wideband spread spectrum digital cellular system,TIA/EIA/IS-96, Feb. 1996.[6]B. Adil, S. Eyal, A silence compression scheme for use with G.729 optimized for V.70 digital simultaneous voice and data applications, IEEE Comm. Mag., 1997, 35(9), 64 73.[7]ITU-T Draft G.723, Dual Rate Speech Coder for Multimedia Communications Transmitting at 5.3 and 6.3 kbit/s, July 1995. -
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