变码率分类型实时语音声码器

本文提出的声码器将语音分成静音、清音、浊音和混合音四类。用自适应方法进行分频带清浊音判决和有声／无声判决，提高了分类算法的稳定性、准确性和灵活性、准确性和灵活性，还保持了混合语音的音质，且无须对清浊音判决结果进行编码。对清音和浊音的频谱分别采用不同的ＬＳＰ量化表进行编码，从而用标量量化器替代子矢量量化器，降低了复杂度。声码器的码率最高２．４ｋｂｐｓ，最低为１００ｂｐｓ，平均码率１．４ｋｂｐｓ。实时

Variable-Rate Phonetic Classified Real-time Speech Vocoder

Speech vocoder presented in this paper classifies input speech into silent,unvoiced,voiced and mixed classes.Adaptive multi band classification algorithm is applied for unvoiced/voiced decision and active/inactive decision.Such algorithm has improved robustness,accuracy and flexibility of classification,and the quality of mixed speech is also maintained without coding of U/V decision vector.Spectra of unvoiced and voiced classes are encoded with different LSP quantization tables,respectively,and then a scale quantizer could replace a vector quantizer,therefore less complexity is achieved.Bit rates of the vocoder are maximum 2.4kbps and minimum 0.1kbps,and average bit rate is 1.4kbps.A real time software implementation of the vocoder has 0.3 second of system delay.A 40MHz TMS320C50 fixed point DSP is chosen for real time implementation of the decoder and synthesizer parts,and the average computation is 11.3MIPS.