Biquad cleanup

gritwave · Feb 24, 2024 · 9ee1e76 · 9ee1e76
1 parent 34bebab
commit 9ee1e76
Showing 1 changed file with 60 additions and 47 deletions.
diff --git a/lib/grit/audio/filter/biquad.hpp b/lib/grit/audio/filter/biquad.hpp
@@ -18,30 +18,8 @@ struct BiquadCoefficients
     using value_type = Float;
     using SampleType = Float;
 
-    [[nodiscard]] static constexpr auto makeBypass() -> etl::array<Float, 6>
-    {
-        return {Float(1), Float(0), Float(0), Float(1), Float(0), Float(0)};
-    }
-
-    [[nodiscard]] static constexpr auto makeLowPass(Float cutoff, Float Q, Float sampleRate) -> etl::array<Float, 6>
-    {
-        auto const omega0 = Float(2) * static_cast<Float>(etl::numbers::pi) * cutoff / sampleRate;
-        auto const d      = Float(1) / Q;
-        auto const cos0   = etl::cos(omega0);
-        auto const sin0   = etl::sin(omega0);
-        auto const beta   = Float(0.5) * ((Float(1) - (d * Float(0.5)) * sin0) / (Float(1) + (d * Float(0.5)) * sin0));
-        auto const gamma  = (Float(0.5) + beta) * cos0;
-
-        auto const b0 = (Float(0.5) + beta - gamma) * Float(0.5);
-        auto const b1 = Float(0.5) + beta - gamma;
-        auto const b2 = b0;
-
-        auto const a0 = Float(1);
-        auto const a1 = Float(-2) * gamma;
-        auto const a2 = Float(2) * beta;
-
-        return {b0, b1, b2, a0, a1, a2};
-    }
+    [[nodiscard]] static constexpr auto makeBypass() -> etl::array<Float, 6>;
+    [[nodiscard]] static constexpr auto makeLowPass(Float cutoff, Float Q, Float sampleRate) -> etl::array<Float, 6>;
 };
 
 /// \brief 2nd order IIR filter using the transpose direct form 2 structure.
@@ -55,30 +33,10 @@ struct Biquad
 
     constexpr Biquad() = default;
 
-    constexpr auto setCoefficients(etl::span<Float const, 6> coefficients) -> void
-    {
-        etl::copy(coefficients.begin(), coefficients.end(), _coefficients.begin());
-    }
+    constexpr auto setCoefficients(etl::span<Float const, 6> coefficients) -> void;
+    constexpr auto reset() -> void;
 
-    constexpr auto reset() -> void
-    {
-        _z[0] = Float(0);
-        _z[1] = Float(0);
-    }
-
-    [[nodiscard]] constexpr auto operator()(Float x) -> Float
-    {
-        auto const b0 = _coefficients[Index::B0];
-        auto const b1 = _coefficients[Index::B1];
-        auto const b2 = _coefficients[Index::B2];
-        auto const a1 = _coefficients[Index::A1];
-        auto const a2 = _coefficients[Index::A2];
-
-        auto const y = b0 * x + _z[0];
-        _z[0]        = b1 * x - a1 * y + _z[1];
-        _z[1]        = b2 * x - a2 * y;
-        return y;
-    }
+    [[nodiscard]] constexpr auto operator()(Float x) -> Float;
 
 private:
     enum Index
@@ -96,4 +54,59 @@ struct Biquad
     etl::array<Float, 2> _z{};
 };
 
+template<etl::floating_point Float>
+constexpr auto BiquadCoefficients<Float>::makeBypass() -> etl::array<Float, 6>
+{
+    return {Float(1), Float(0), Float(0), Float(1), Float(0), Float(0)};
+}
+
+template<etl::floating_point Float>
+constexpr auto BiquadCoefficients<Float>::makeLowPass(Float cutoff, Float Q, Float sampleRate) -> etl::array<Float, 6>
+{
+    auto const omega0 = Float(2) * static_cast<Float>(etl::numbers::pi) * cutoff / sampleRate;
+    auto const d      = Float(1) / Q;
+    auto const cos0   = etl::cos(omega0);
+    auto const sin0   = etl::sin(omega0);
+    auto const beta   = Float(0.5) * ((Float(1) - (d * Float(0.5)) * sin0) / (Float(1) + (d * Float(0.5)) * sin0));
+    auto const gamma  = (Float(0.5) + beta) * cos0;
+
+    auto const b0 = (Float(0.5) + beta - gamma) * Float(0.5);
+    auto const b1 = Float(0.5) + beta - gamma;
+    auto const b2 = b0;
+
+    auto const a0 = Float(1);
+    auto const a1 = Float(-2) * gamma;
+    auto const a2 = Float(2) * beta;
+
+    return {b0, b1, b2, a0, a1, a2};
+}
+
+template<etl::floating_point Float>
+constexpr auto Biquad<Float>::setCoefficients(etl::span<Float const, 6> coefficients) -> void
+{
+    etl::copy(coefficients.begin(), coefficients.end(), _coefficients.begin());
+}
+
+template<etl::floating_point Float>
+constexpr auto Biquad<Float>::reset() -> void
+{
+    _z[0] = Float(0);
+    _z[1] = Float(0);
+}
+
+template<etl::floating_point Float>
+constexpr auto Biquad<Float>::operator()(Float x) -> Float
+{
+    auto const b0 = _coefficients[Index::B0];
+    auto const b1 = _coefficients[Index::B1];
+    auto const b2 = _coefficients[Index::B2];
+    auto const a1 = _coefficients[Index::A1];
+    auto const a2 = _coefficients[Index::A2];
+
+    auto const y = b0 * x + _z[0];
+    _z[0]        = b1 * x - a1 * y + _z[1];
+    _z[1]        = b2 * x - a2 * y;
+    return y;
+}
+
 }  // namespace grit