Formant weighted vector quantization of LPC excitation harmonic spectral amplitudes

摘要

A method of quantizing harmonic amplitudes (FIG. 3), used in a speech encoder (10). The method compares variable dimension input vectors to fixed dimension codebook vectors, by first sampling each codebook vector so that it is converted to a vector having the same dimension as the input vector (FIG. 3, step 35). The resulting codebook vector is compared to the input vector (step 37). The difference (error) is weighted in favor of low frequency harmonics. Also, the weighting favors formant amplitudes so that they are quantized more accurately than formant nulls (FIG. 3, step 38; FIG. 5).