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 echo_generator(void)
{
echo_output = in_fir;
// Produce First echo
echo_output = add_fr1x16(echo_output, multr_fr1x16(0x1000, echo_delayed_input[echo_reader_first]));
// Produce Second echo
echo_output = add_fr1x16(echo_output, multr_fr1x16(0x2000, echo_delayed_input[echo_reader_second]));
// Produce Third echo
echo_output = add_fr1x16(echo_output, multr_fr1x16(0x4000, echo_delayed_input[echo_reader_third]));
echo_delayed_input[echo_writer] = in_fir; //Store the current input in the echo delay buffer
//Increment the echo buffer readers
echo_writer++;
echo_reader_first++;
echo_reader_second++;
echo_reader_third++;
if(echo_writer == echo_TAP_NUM)
{
echo_writer = 0;
}
if(echo_reader_first == echo_TAP_NUM)
{
echo_reader_first = 0;
}
if(echo_reader_second == echo_TAP_NUM)
{
echo_reader_second = 0;
}
if(echo_reader_third == echo_TAP_NUM)
{
echo_reader_third = 0;
}
}
