CS5396 CS5397

38

DS229PP2xC

APPENDIX C: PSYCHOACOUSTIC FILTER

The psychoacoustic filter in the CS5396 is based on the paper: "Robert A. Wannamaker, Psychoacous-

tically Optimal Noise Shaping, Journal of the Audio Engineering Society, Vol 40, No 7/8, 1992 July/Au-

gust." The default coefficients in the CS5396 are the FIR 9-tap filter coefficients described in Table 3 of

the paper. Since the effective noise shaping function is (1-H), the CS5396 registers save the (1-H) func-

tion coefficients. Therefore, the negative of each filter coefficient is stored in the registers. Each coefficient

is represented as a binary 2’s complement number where the 4 MSB’s represent the whole number of the

coefficient and the 4 LSB’s represent the fractional portion truncated to 4 binary bits.

Default Coefficients as listed in "Robert A. Wannamaker, Psychoacoustically Optimal Noise Shaping”

a1 = 2.412

a2 = -3.370

a3 = 3.937

a4 = -4.174

a5 = 3.353

a6 = -2.205

a7 = 1.281

a8 = -0.569

a9 = 0.0847

Coefficient conversion example 1:

a1 = 2.412

a1 = (0010.0110) binary repesentation with the fractional portion truncated to 4 bits.

-a1 = -(0010.0110) binary representation

-a1 = 1101.1010 in two’s complement

this value is stored in register 10h.

Coefficient conversion example 2:

a2 = -3.370

-a2 = 3.370

-a2 = 0011.0101

binary repesentation with the fractional portion truncated to 4 bits.

-a2 = 0011.0101 in 2's complement

this value is stored in register 11h.