Hybrid Adaptive Quantization for Speech Coding

This correspondence describes a new quantization technique called hybrid adaptive quantization (HAQ) that uses instantaneous [1], [2] as well as syllabic [3] adaptation of the step size. Two types of instantaneous adaptive algorithms have been used-Jayant´s adaptive quantizer (JAQ) and the incremental adaptive quantizer (IAQ). Computer simulations have been performed for a sine-wave, correlated Gaussian signal and digitized speech. Signal-to-noise ratio (SNR) computation for PCM and DPCM coders indicates that the hybrid technique is superior to the normal adaptive quantizer, when both have the same ratio of maximum to minimum step size.