Dima353/openal-soft
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Document the different filter types, and combine some split lines

Browse Source
This commit is contained in:
Chris Robinson
2014-05-17 02:09:43 -07:00
parent c5b25ba2a7
commit 1efddac3db
2 changed files with 20 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files
OpenAL32/Include/alFilter.h
+6
View File
@@ -15,12 +15,18 @@ extern "C" {
* http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt */
typedef enum ALfilterType {
/** EFX-style low-pass filter, specifying a gain and reference frequency. */
ALfilterType_HighShelf,
/** EFX-style high-pass filter, specifying a gain and reference frequency. */
ALfilterType_LowShelf,
/** Peaking filter, specifying a gain, reference frequency, and bandwidth. */
ALfilterType_Peaking,
/** Low-pass cut-off filter, specifying a cut-off frequency and bandwidth. */
ALfilterType_LowPass,
/** High-pass cut-off filter, specifying a cut-off frequency and bandwidth. */
ALfilterType_HighPass,
/** Band-pass filter, specifying a center frequency and bandwidth. */
ALfilterType_BandPass,
} ALfilterType;
OpenAL32/alFilter.c
+14 -36
View File
@@ -349,44 +349,22 @@ void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat g
switch(type)
{
case ALfilterType_HighShelf:
alpha = sinf(w0) / 2.0f * sqrtf((gain + 1.0f/gain) *
(1.0f/0.75f - 1.0f) + 2.0f);
filter->b[0] = gain * ((gain + 1.0f) +
(gain - 1.0f) * cosf(w0) +
2.0f * sqrtf(gain) * alpha);
filter->b[1] = -2.0f * gain * ((gain - 1.0f) +
(gain + 1.0f) * cosf(w0));
filter->b[2] = gain * ((gain + 1.0f) +
(gain - 1.0f) * cosf(w0) -
2.0f * sqrtf(gain) * alpha);
filter->a[0] = (gain + 1.0f) -
(gain - 1.0f) * cosf(w0) +
2.0f * sqrtf(gain) * alpha;
filter->a[1] = 2.0f * ((gain - 1.0f) -
(gain + 1.0f) * cosf(w0));
filter->a[2] = (gain + 1.0f) -
(gain - 1.0f) * cosf(w0) -
2.0f * sqrtf(gain) * alpha;
alpha = sinf(w0)/2.0f*sqrtf((gain + 1.0f/gain)*(1.0f/0.75f - 1.0f) + 2.0f);
filter->b[0] = gain*((gain+1.0f) + (gain-1.0f)*cosf(w0) + 2.0f*sqrtf(gain)*alpha);
filter->b[1] = -2.0f*gain*((gain-1.0f) + (gain+1.0f)*cosf(w0) );
filter->b[2] = gain*((gain+1.0f) + (gain-1.0f)*cosf(w0) - 2.0f*sqrtf(gain)*alpha);
filter->a[0] = (gain+1.0f) - (gain-1.0f)*cosf(w0) + 2.0f*sqrtf(gain)*alpha;
filter->a[1] = 2.0f* ((gain-1.0f) - (gain+1.0f)*cosf(w0) );
filter->a[2] = (gain+1.0f) - (gain-1.0f)*cosf(w0) - 2.0f*sqrtf(gain)*alpha;
break;
case ALfilterType_LowShelf:
alpha = sinf(w0) / 2.0f * sqrtf((gain + 1.0f / gain) *
(1.0f / 0.75f - 1.0f) + 2.0f);
filter->b[0] = gain * ((gain + 1.0f) -
(gain - 1.0f) * cosf(w0) +
2.0f * sqrtf(gain) * alpha);
filter->b[1] = 2.0f * gain * ((gain - 1.0f) -
(gain + 1.0f) * cosf(w0));
filter->b[2] = gain * ((gain + 1.0f) -
(gain - 1.0f) * cosf(w0) -
2.0f * sqrtf(gain) * alpha);
filter->a[0] = (gain + 1.0f) +
(gain - 1.0f) * cosf(w0) +
2.0f * sqrtf(gain) * alpha;
filter->a[1] = -2.0f * ((gain - 1.0f) +
(gain + 1.0f) * cosf(w0));
filter->a[2] = (gain + 1.0f) +
(gain - 1.0f) * cosf(w0) -
2.0f * sqrtf(gain) * alpha;
alpha = sinf(w0)/2.0f*sqrtf((gain + 1.0f/gain)*(1.0f/0.75f - 1.0f) + 2.0f);
filter->b[0] = gain*((gain+1.0f) - (gain-1.0f)*cosf(w0) + 2.0f*sqrtf(gain)*alpha);
filter->b[1] = 2.0f*gain*((gain-1.0f) - (gain+1.0f)*cosf(w0) );
filter->b[2] = gain*((gain+1.0f) - (gain-1.0f)*cosf(w0) - 2.0f*sqrtf(gain)*alpha);
filter->a[0] = (gain+1.0f) + (gain-1.0f)*cosf(w0) + 2.0f*sqrtf(gain)*alpha;
filter->a[1] = -2.0f* ((gain-1.0f) + (gain+1.0f)*cosf(w0) );
filter->a[2] = (gain+1.0f) + (gain-1.0f)*cosf(w0) - 2.0f*sqrtf(gain)*alpha;
break;
case ALfilterType_Peaking:
alpha = sinf(w0) * sinhf(logf(2.0f) / 2.0f * bandwidth * w0 / sinf(w0));