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LADSPA Multiband EQ (mbeq_1197) bugfix #1885

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Corrected Hann (raised cosine) window function.

Corrected output-windowing logic and recalculated correction factor
for window type. Tested against white noise & triple_osc output.
This commit is contained in:
Greg Simpson
2015-03-23 17:44:55 -07:00
parent de9f879dde
commit 6db4c9007e
1 changed files with 7 additions and 4 deletions
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11
plugins/LadspaEffect/swh/mbeq_1197.c
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@@ -286,11 +286,10 @@ static LADSPA_Handle instantiateMbeq(
// Create raised cosine window table
for (i=0; i < FFT_LENGTH; i++) {
window[i] = -0.5f*cos(2.0f*M_PI*(double)i/(double)FFT_LENGTH)+0.5f;
window[i] *= 2.0f;
window[i] = -0.5f * cos(2.0f*M_PI*(double)i/(double)FFT_LENGTH) + 0.5f;
}
// Create db->coeffiecnt lookup table
// Create db->coefficient lookup table
db_table = malloc(1000 * sizeof(float));
for (i=0; i < 1000; i++) {
db = ((float)i/10) - 70;
@@ -472,8 +471,12 @@ static void runMbeq(LADSPA_Handle instance, unsigned long sample_count) {
// Window into the output accumulator
for (i = 0; i < FFT_LENGTH; i++) {
out_accum[i] += 0.9186162f * window[i] * real[i]/(FFT_LENGTH * OVER_SAMP);
// correction factor for window measured from white noise
// reduce intermediate output by (number of coefficients) * OVER_SAMP
out_accum[i] += real[i] * window[i] * 1.27519f /
((FFT_LENGTH/2) * OVER_SAMP);
}
for (i = 0; i < step_size; i++) {
out_fifo[i] = out_accum[i];
}