Add a function for 1-pole filtering

1 files changed, 12 insertions, 0 deletions

diff --git a/OpenAL32/Include/alFilter.h b/OpenAL32/Include/alFilter.h
index 86ada5ef..754b0b6f 100644
--- a/OpenAL32/Include/alFilter.h
+++ b/OpenAL32/Include/alFilter.h
@@ -49,6 +49,18 @@ static __inline ALfloat lpFilter2P(FILTER *iir, ALuint offset, ALfloat input)
     return output;
 }
 
+static __inline ALfloat lpFilter1P(FILTER *iir, ALuint offset, ALfloat input)
+{
+    ALfloat *history = &iir->history[offset];
+    ALfloat a = iir->coeff;
+    ALfloat output = input;
+
+    output = output + (history[0]-output)*a;
+    history[0] = output;
+
+    return output;
+}
+
 
 #define AL_FILTER_TYPE                                     0x8001