added q value parameter to be passed to filter functions (#515)

I have added a 2nd parameter to the filter functions low_pass, high_pass, to_low_pass, and to_high pass; allowing a q value to be passed along with the frequency.

Co-authored-by: David Kleingeld <git@davidsk.dev>

src/source/blt.rs

@@ -7,12 +7,27 @@ use crate::Source;
 
 /// Internal function that builds a `BltFilter` object.
 pub fn low_pass<I>(input: I, freq: u32) -> BltFilter<I>
+where
+    I: Source<Item = f32>,
+{
+    low_pass_with_q(input, freq, 0.5)
+}
+
+pub fn high_pass<I>(input: I, freq: u32) -> BltFilter<I>
+where
+    I: Source<Item = f32>,
+{
+    high_pass_with_q(input, freq, 0.5)
+}
+
+/// Same as low_pass but allows the q value (bandwidth) to be changed
+pub fn low_pass_with_q<I>(input: I, freq: u32, q: f32) -> BltFilter<I>
 where
     I: Source<Item = f32>,
 {
     BltFilter {
         input,
-        formula: BltFormula::LowPass { freq, q: 0.5 },
+        formula: BltFormula::LowPass { freq, q },
         applier: None,
         x_n1: 0.0,
         x_n2: 0.0,
@@ -21,13 +36,14 @@ where
     }
 }
 
-pub fn high_pass<I>(input: I, freq: u32) -> BltFilter<I>
+/// Same as high_pass but allows the q value (bandwidth) to be changed
+pub fn high_pass_with_q<I>(input: I, freq: u32, q: f32) -> BltFilter<I>
 where
     I: Source<Item = f32>,
 {
     BltFilter {
         input,
-        formula: BltFormula::HighPass { freq, q: 0.5 },
+        formula: BltFormula::HighPass { freq, q },
         applier: None,
         x_n1: 0.0,
         x_n2: 0.0,
@@ -50,13 +66,23 @@ pub struct BltFilter<I> {
 impl<I> BltFilter<I> {
     /// Modifies this filter so that it becomes a low-pass filter.
     pub fn to_low_pass(&mut self, freq: u32) {
-        self.formula = BltFormula::LowPass { freq, q: 0.5 };
-        self.applier = None;
+        self.to_low_pass_with_q(freq, 0.5);
     }
 
     /// Modifies this filter so that it becomes a high-pass filter
     pub fn to_high_pass(&mut self, freq: u32) {
-        self.formula = BltFormula::HighPass { freq, q: 0.5 };
+        self.to_high_pass_with_q(freq, 0.5);
+    }
+
+    /// Same as to_low_pass but allows the q value (bandwidth) to be changed
+    pub fn to_low_pass_with_q(&mut self, freq: u32, q: f32) {
+        self.formula = BltFormula::LowPass { freq, q };
+        self.applier = None;
+    }
+
+    /// Same as to_high_pass but allows the q value (bandwidth) to be changed
+    pub fn to_high_pass_with_q(&mut self, freq: u32, q: f32) {
+        self.formula = BltFormula::HighPass { freq, q };
         self.applier = None;
     }
 

src/source/mod.rs

@@ -343,6 +343,7 @@ where
         blt::low_pass(self, freq)
     }
 
+    /// Applies a high-pass filter to the source.
     #[inline]
     fn high_pass(self, freq: u32) -> BltFilter<Self>
     where
@@ -351,6 +352,26 @@ where
     {
         blt::high_pass(self, freq)
     }
+
+    /// Applies a low-pass filter to the source while allowing the q (badnwidth) to be changed.
+    #[inline]
+    fn low_pass_with_q(self, freq: u32, q: f32) -> BltFilter<Self>
+    where
+        Self: Sized,
+        Self: Source<Item = f32>,
+    {
+        blt::low_pass_with_q(self, freq, q)
+    }
+
+    /// Applies a high-pass filter to the source while allowing the q (badnwidth) to be changed.
+    #[inline]
+    fn high_pass_with_q(self, freq: u32, q: f32) -> BltFilter<Self>
+    where
+        Self: Sized,
+        Self: Source<Item = f32>,
+    {
+        blt::high_pass_with_q(self, freq, q)
+    }
 }
 
 impl<S> Source for Box<dyn Source<Item = S>>