Novel low-band phase representation for low bit-rate speech coding

Vector Quantization (VQ) has been extensively used in speech vocoders. Phase information is often ignored or coarsely represented in parametric coders because of the difficulties facing phase quantization. This paper introduces a novel distortion measure for the low-band speech signal that takes phase information into consideration, with no increase in the bit-rate. This measure has been used in the construction of a segmental vocoder, which is using the pitch period as segments. A description of the proposed Time-Domain PhaseAware (TDPA) distortion measure is given and compared to the use of the MFCC as a distortion measure showing the effect of the phase information represented in the TDPA model on improving the inter-frame correlation of the synthesized speech. Finally, the performance of the TDPA is evaluated using the Segmental Signal-to-Noise Ratio (SNR), and Spectral Distortion (SD). Speech quality is evaluated using the recently standardized objective quality measure PESQ.