Implement some samples rate conversions

examples/beep.rs

@@ -20,11 +20,9 @@ fn main() {
     loop {
         let mut buffer = channel.append_data(1, cpal::SamplesRate(44100));
 
-        for sample in buffer.chunks_mut(1) {
+        for sample in buffer.iter_mut() {
             let value = data_source.next().unwrap();
-
+            *sample = value;
-            sample[0] = value;
-            //sample[1] = value;
         }
     }
 }

src/conversions.rs

@@ -7,6 +7,35 @@ This includes conversion between samples formats, channels or sample rates.
 pub fn convert_samples_rate<T>(input: &[T], from: ::SamplesRate, to: ::SamplesRate) -> Vec<T>
                                where T: Copy
 {
+    let from = from.0;
+    let to = to.0;
+
+    // if `from` is a multiple of `to` (for example `from` is 44100 and `to` is 22050),
+    // then we simply skip some samples
+    if from % to  == 0 {
+        let mut result = Vec::new();
+        for element in input.chunks((from / to) as uint) {
+            result.push(element[0]);
+        }
+        return result;
+    }
+
+    // if `to` is a multiple of `from` (for example `to` is 44100 and `from` is 22050)
+    // TODO: dumb algorithm
+    // FIXME: doesn't take channels into account
+    if to % from  == 0 {
+        let mut result = Vec::new();
+        for element in input.windows(2) {
+            for _ in range(0, (to / from) as uint) {
+                result.push(element[0]);
+            }
+        }
+        for _ in range(0, (to / from) as uint) {
+            result.push(*input.last().unwrap());
+        }
+        return result;
+    }
+
     unimplemented!()
 }
 
@@ -32,10 +61,10 @@ pub fn convert_channels<T>(input: &[T], from: ::ChannelsCount, to: ::ChannelsCou
     result
 }
 
-#[cfg(test)]
+/*#[cfg(test)]
 mod test {
     #[test]
     fn test_convert_channels() {
 
     }
-}
+}*/

src/lib.rs

@@ -20,7 +20,7 @@ pub type ChannelsCount = u16;
 
 /// 
 #[deriving(Show, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-pub struct SamplesRate(pub u16);
+pub struct SamplesRate(pub u32);
 
 /// Represents a buffer that must be filled with audio data.
 ///

src/wasapi/mod.rs

@@ -33,7 +33,7 @@ impl Channel {
     }
 
     pub fn get_samples_rate(&self) -> ::SamplesRate {
-        ::SamplesRate(self.samples_per_second as u16)
+        ::SamplesRate(self.samples_per_second as u32)
     }
 
     pub fn get_samples_format(&self) -> ::SampleFormat {