A Low-Bit Rate Segment Vocoder Using Minimum Residual Energy Criteria

In speech coding, segment vocoders offer good intelligibility at low bit rates. A segment vocoder has four basic components: segmentation of input speech, segment quantization, residual quantization, and synthesis of speech. Most segment vocoders use a recognition approach to segment quantization. In this paper, the authors assume a different approach to segment quantization. The segmental unit is a syllable and the segment codebook stores the sequence of LPC vectors. During the encoding process the speech segment is quantized using the sequence of LPC vectors that result in the smallest residual energy. PESQ scores indicate that this vocoder achieves better quality compared to that of a corresponding vocoder that uses a speech recognition framework.