基于線性預(yù)測系數(shù)自適應(yīng)前后向量化的可變速率MELP語音編碼
VARIABLE-RATE MELP SPEECH CODER BASED ON ADAPTIVE FORWARD-BACKWARD QUANTIZATION OF LINEAR PREDICTIVE COEFFICIENTS
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摘要: 該文基于LPC的自適應(yīng)前后向量化技術(shù),提出了一種可變速率的混合激勵線性預(yù)測MELP語音編碼算法。該算法中,采用當(dāng)前語音幀(前向LPC)或前面某幀已合成語音幀(后向LPC)進(jìn)行線性預(yù)測,當(dāng)采用后向LPC時,只需傳輸時間序列編碼,故減少了LPC系數(shù)的平均編碼比特。計(jì)算機(jī)模擬表明,該算法與標(biāo)準(zhǔn)MELP算法合成的語音質(zhì)量相當(dāng),但顯著減少了LPC的傳輸帶寬,從而明顯降低了MELP平均編碼速率。Abstract: In this paper, based on LPC adaptive forward-backward quantization, a novel variable-rate MELP speech coder is proposed, in which linear prediction is done by using either the current (forward LPC) or previously decoded (backward LPC) speech frames. The backward LPC scheme shall be applied, i.e., the LPC coefficients based on the previously decoded optimal speech frame are used to encode the current frame and only the time sequence code shall be transmitted to the decoder, so, average LPC bit number becomes smaller. Computer simulation shows significant average overall bit rate reduction is achieved without compromising the decoded speech quality.
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Federal Information Processing Standards Publication (MELP), Jan. 7, 1998, Draft. ［2］A. Gersho, Advanced in speech and audio compression, Proc. IEEE, 1994, 82(6), 900-918.[2]Tozsef Vass, Adaptive forward-backward quantizer for low bit rate high-quality coding, IEEE Trans. on Speech and Audio Processing, 1997, 5(6), 552 557.[3]J. chen et al., A low-delay CELP coder for the CCITT 16kb/s speech coding standard, IEEE J.on Select. Areas Commun., 1992, 10(6), 830-849. -
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