diff options
Diffstat (limited to 'intern/audaspace/FX/AUD_LowpassFactory.cpp')
| -rw-r--r-- | intern/audaspace/FX/AUD_LowpassFactory.cpp | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/intern/audaspace/FX/AUD_LowpassFactory.cpp b/intern/audaspace/FX/AUD_LowpassFactory.cpp index dfef0f6f7c3..9244e07631b 100644 --- a/intern/audaspace/FX/AUD_LowpassFactory.cpp +++ b/intern/audaspace/FX/AUD_LowpassFactory.cpp @@ -24,7 +24,13 @@ */ #include "AUD_LowpassFactory.h" -#include "AUD_LowpassReader.h" +#include "AUD_IIRFilterReader.h" + +#include <cmath> + +#ifndef M_PI +#define M_PI 3.14159265358979323846 +#endif AUD_LowpassFactory::AUD_LowpassFactory(AUD_IFactory* factory, float frequency, float Q) : @@ -36,5 +42,20 @@ AUD_LowpassFactory::AUD_LowpassFactory(AUD_IFactory* factory, float frequency, AUD_IReader* AUD_LowpassFactory::createReader() const { - return new AUD_LowpassReader(getReader(), m_frequency, m_Q); + AUD_IReader* reader = getReader(); + + // calculate coefficients + float w0 = 2 * M_PI * m_frequency / reader->getSpecs().rate; + float alpha = sin(w0) / (2 * m_Q); + float norm = 1 + alpha; + float c = cos(w0); + std::vector<float> a, b; + a.push_back(1); + a.push_back(-2 * c / norm); + a.push_back((1 - alpha) / norm); + b.push_back((1 - c) / (2 * norm)); + b.push_back((1 - c) / norm); + b.push_back(b[0]); + + return new AUD_IIRFilterReader(reader, b, a); } |