struct Coef get_shelving_coef(void)
{
struct Coef coefficients;
coefficients.b0 = float_to_fr16(0.46546409);
coefficients.b1 = float_to_fr16(-0.77571291);
coefficients.b2 = float_to_fr16(0.34163607);
coefficients.a1 = float_to_fr16(-0.38094923);
coefficients.a2 = float_to_fr16(0.16233647);
return coefficients;
}
void pre_emphasis(fract16 data[], int arr_length, struct Coef shelving_coef)
{
fract16 xBuffer[BUFFER_SIZE];
// input buffer
fract16 yBuffer[BUFFER_SIZE];
// output buffer
int current;
for (current = 0; current < BUFFER_SIZE; ++current) {
xBuffer[current] = yBuffer[current] = float_to_fr16(0.0);
}
current = 0;
int index;
for (index = 0; index < arr_length; index++) {
fract16 temp_b0 = mult_fr1x16(shelving_coef.b0, data[index]);
fract16 temp_b1 = mult_fr1x16(shelving_coef.b1, xBuffer[INDEX(current-1)]);
fract16 temp_b2 = mult_fr1x16(shelving_coef.b2, xBuffer[INDEX(current-2)]);
fract16 temp_a1 = mult_fr1x16(shelving_coef.a1, yBuffer[INDEX(current-1)]);
fract16 temp_a2 = mult_fr1x16(shelving_coef.a2, yBuffer[INDEX(current-2)]);
fract16 temp_b = add_fr1x16(add_fr1x16(temp_b0, temp_b1), temp_b2);
fract16 temp_a = add_fr1x16(temp_a1, temp_a2);
fract16 temp = sub_fr1x16(temp_b, temp_a);
yBuffer[current] = shl_fr1x16(temp, 2);
xBuffer[current] = data[index]; //input
data[index] = yBuffer[current]; //output
current++;
current %= BUFFER_SIZE;
}
}
void adaptive_lms(void)
{
// First, produce y_lms.
fir_fr16(pointer, pointer_out, 1, &state); //Call the in-built efficient FIR filter.
// Find the error signal
adder_unit();
// Calculate the step size------------------------------------
// If you do not want to update the step size automatically,
// comment this section of step size calculation between the
// top and bottom comments.
_NLMS_step_updater_sum(sum_int_p, sum_fract_p, &state);
sum = sum_int + fr16_to_float(sum_fract);
meu = 1 / (0.5 + sum); //alpha = 1 and gamma = 0.5.
if(meu>=1)
{
step_size=0x7fff;
}
else
{
step_size = float_to_fr16(meu);
}
//Step size calculation ends----------------------------------
// Lastly, update the filter coefficients
_coeff_updater(error_sig, step_size, &state);
}
int main() {
fract16 data[WINDOW_LENGTH];
int index;
for (index = 0; index < WINDOW_LENGTH; index++) {
data[index] = float_to_fr16(test_input[index]);
}
struct Coef shelving_coef = get_shelving_coef();
pre_emphasis(data, WINDOW_LENGTH, shelving_coef);
for (index = 0; index < WINDOW_LENGTH; ++index) {
float test = fr16_to_float(data[index]);
// printf("%f\n", fr16_to_float(data[index]));
}
return 0;
}
