Patent ID: 8271273

Claim:
A method of improving a perceptual weighting filter W(z) or a perceptual noise shaping filter F(z)=W(z)−1, used to enhance perceptual performance of a G.711 codec, the method comprising: i. inputting an unquantized signal sample to a G.711 encoder; ii. encoding said unquantized signal via the G.711 encoder to produce a coded bitstream using W(z) or F(z) as follows: W ⁡ ( z ) = A ⁡ ( z / α ) = 1 + ∑ i = 1 P ⁢ ⁢ a i · α i · z - i , i = 1 , 2 , … ⁢ , P F ⁡ ( z ) = W ⁡ ( z ) - 1 = ∑ i = 1 P ⁢ ⁢ a i · α i · z - i , i = 1 , 2 , … ⁢ , P A ⁡ ( z ) = 1 + ∑ i = 1 P ⁢ ⁢ a i · z - i , i = 1 , 2 , … ⁢ , P where A(z) is an LP (Linear Prediction) predictor obtained from analyzing an input signal, {a i , i=1, 2, . . . , P} are the LP predictor coefficients, P is the LP predictor order and α is a controlling parameter controlling W(z) or F(z), wherein the controlling parameter α depends on an input signal level; when the input signal level becomes low (towards zero), α is towards 0; iii. receiving said bitstream at a decoder; and iv. outputting an enhanced decoded signal.