[feat]: Filter (#18)

closes #16

Reviewed-on: #18

src/BandPassFilter.cpp

@@ -0,0 +1,23 @@
+#include "BandPassFilter.h"
+
+BandPassFilter::BandPassFilter(/* args */) {}
+
+BandPassFilter::BandPassFilter(Filter* filter) {
+    m_freq = filter->GetFreq();
+    m_q = filter->GetRes();
+    m_order = filter->GetPeakGain();
+}
+
+BandPassFilter::BandPassFilter(float freq, float res, float q) {}
+
+BandPassFilter::~BandPassFilter() {}
+
+void BandPassFilter::CalculateCoefficients() {
+    CalculateNormals();
+    m_norm = 1 / (1 + m_k / m_q + m_k * m_k);
+    m_a0 = m_k / m_q * m_norm;
+    m_a1 = 0;
+    m_a2 = -m_a0;
+    m_b1 = 2 * (m_k * m_k - 1) * m_norm;
+    m_b2 = (1 - m_k / m_q + m_k * m_k) * m_norm;
+}