Merge pull request #125 from card-io-ecg/iir

Fix iir filters
card-io-ecg · Sep 30, 2023 · 31ec78b · 31ec78b
2 parents b781be9 + e38c19e
commit 31ec78b
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Showing 4 changed files with 307 additions and 35 deletions.
diff --git a/macros/src/filter.rs b/macros/src/filter.rs
@@ -154,6 +154,12 @@ fn iir(args: FilterSpec, ty: FilterBandType) -> TokenStream {
     // Strip off always-1 coefficient
     assert!(a.remove(0) == 1.0);
 
+    // we reverse a to avoid having to reverse it during filtering
+    a.reverse();
+
+    // b seems to be returned in the wrong order
+    b.reverse();
+
     let n = a.len();
 
     quote! {

diff --git a/signal-processing/src/filter/dyn_iir.rs b/signal-processing/src/filter/dyn_iir.rs
@@ -68,6 +68,12 @@ where
         // Strip off always-1 coefficient
         assert!(a.remove(0) == 1.0);
 
+        // we reverse a to avoid having to reverse it during filtering
+        a.reverse();
+
+        // b seems to be returned in the wrong order
+        b.reverse();
+
         let denom_coeffs = a.into_boxed_slice();
         let num_coeffs = b.into_boxed_slice();
 
@@ -97,3 +103,159 @@ impl<T: DynFilterType, const N: usize> IirFilter for DynIir<T, N> {
         self.filter.transfer_coeff_at(w)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_iir_no_input() {
+        let input = [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.];
+        let expectation = [0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<HighPass, 1>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_lowpass_iir_impluse_response_order1() {
+        let input = [0., 1., 0., 0., 0., 0., 0.];
+        let expectation = [0.0000, 0.2452, 0.3702, 0.1886, 0.0961, 0.0490, 0.0250];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<LowPass, 1>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_lowpass_iir_step_response_order1() {
+        let input = [0., 1., 1., 1., 1., 1., 1.];
+        let expectation = [0.0000, 0.2452, 0.6154, 0.8041, 0.9002, 0.9491, 0.9741];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<LowPass, 1>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_highpass_iir_impluse_response_order1() {
+        let input = [0., 1., 0., 0., 0., 0., 0.];
+        let expectation = [0.0000, 0.7548, -0.3702, -0.1886, -0.0961, -0.0490, -0.0250];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<HighPass, 1>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_highpass_iir_step_response_order1() {
+        let input = [0., 1., 1., 1., 1., 1., 1.];
+        let expectation = [0.0000, 0.7548, 0.3846, 0.1959, 0.0998, 0.0509, 0.0259];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<HighPass, 1>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_lowpass_iir_impluse_response_order2() {
+        let input = [0., 1., 0., 0., 0., 0., 0., 0.];
+        let expectation = [0.0000, 0.0675, 0.2120, 0.2819, 0.2347, 0.1519, 0.0767];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<LowPass, 2>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_lowpass_iir_step_response_order2() {
+        let input = [0., 1., 1., 1., 1., 1., 1.];
+        let expectation = [0.0000, 0.0675, 0.2795, 0.5614, 0.7961, 0.9480, 1.0248];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<LowPass, 2>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_highpass_iir_impluse_response_order2() {
+        let input = [0., 1., 0., 0., 0., 0., 0., 0.];
+        let expectation = [0.0000, 0.6389, -0.5476, -0.2507, -0.0605, 0.0343, 0.0642];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<HighPass, 2>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[test]
+    fn test_highpass_iir_step_response_order2() {
+        let input = [0., 1., 1., 1., 1., 1., 1.];
+        let expectation = [0.0000, 0.6389, 0.0914, -0.1593, -0.2198, -0.1855, -0.1213];
+
+        #[rustfmt::skip]
+        test_filter(
+            DynIir::<HighPass, 2>::design(10.0, 1.0),
+            &input,
+            &expectation,
+            0.0001
+        );
+    }
+
+    #[track_caller]
+    fn test_filter(mut filter: impl Filter, input: &[f32], expectation: &[f32], epsilon: f32) {
+        let mut output = vec![];
+        for sample in input.iter().copied() {
+            if let Some(out_sample) = filter.update(sample) {
+                output.push(out_sample);
+            }
+        }
+
+        let pairs = output.iter().copied().zip(expectation.iter().copied());
+
+        for (out_sample, expectation) in pairs.clone() {
+            assert!(
+                (out_sample - expectation).abs() < epsilon,
+                "[\n  // (output, expectation)\n{}]",
+                pairs
+                    .map(|(a, b)| format!(
+                        "   {} ({a:>7.04}, {b:>7.04})\n",
+                        if (a - b).abs() < epsilon { " " } else { "!" }
+                    ))
+                    .collect::<String>()
+            );
+        }
+    }
+}