diff --git a/src/fir.rs b/src/fir.rs
index 5ee9265..aa7cbee 100644
--- a/src/fir.rs
+++ b/src/fir.rs
@@ -27,18 +27,27 @@ impl<I, const N: usize> Fir<I, N> {
         }
     }
 
-    pub fn process_chunk(&mut self, chunk: &mut IqChunk) {
-        for iq in chunk.samples.iter_mut() {
+    pub fn process_chunk(&mut self, chunk: &IqChunk) -> IqChunk {
+        let mut chunk_out = IqChunk::new();
+
+        for iq in chunk.samples.iter() {
             self.history.push(*iq);
-            let mut y_n = IqSample::default();
-            for k in 0..N {
-                if let Some(sample) = self.history.read_at(k) {
-                    y_n += *sample * self.taps[k];
+
+            // Decimation
+            if self.decimation_index.is_multiple_of(self.decimation_factor) {
+                let mut y_n = IqSample::default();
+                for k in 0..N {
+                    if let Some(sample) = self.history.read_at(k) {
+                        y_n += *sample * self.taps[k];
+                    }
                 }
+
+                chunk_out.samples.push(y_n);
             }
-            *iq = y_n
+
+            self.decimation_index += 1;
         }
-        // TODO: Decimation
+        chunk_out
     }
 }
 
@@ -50,9 +59,10 @@ where
 
     fn next(&mut self) -> Option<Self::Item> {
         match self.inner.next()? {
-            Ok(mut chunk) => {
-                self.process_chunk(&mut chunk);
-                Some(Ok(chunk))
+            Ok(chunk) => {
+                // self.process_chunk(&mut chunk);
+                // Some(Ok(chunk))
+                Some(Ok(self.process_chunk(&chunk)))
             }
             Err(e) => Some(Err(e)),
         }
diff --git a/src/iq_reader.rs b/src/iq_reader.rs
index 35a1a44..2e9cbdd 100644
--- a/src/iq_reader.rs
+++ b/src/iq_reader.rs
@@ -11,6 +11,14 @@ pub struct IqChunk {
     pub samples: Vec<IqSample>,
 }
 
+impl IqChunk {
+    pub fn new() -> Self {
+        IqChunk {
+            samples: Vec::<IqSample>::new(),
+        }
+    }
+}
+
 pub struct FileSource {
     // Buffer
     pub reader: BufReader<File>,
diff --git a/src/main.rs b/src/main.rs
index 2e393f8..48b77ca 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -12,14 +12,15 @@ fn main() -> Result<(), Box<dyn Error>> {
     let source = FileSource::new("test.iq", 32769)?;
 
     // Fir coefs
-    let taps = [1.0; 64];
+    let taps = [0.5; 64];
 
     let pipeline = source
         .agc(20_000_000.0, 1.0, 0.001, 100.0)
         .fir::<64>(taps, 4);
 
     for chunk_r in pipeline {
-        let _chunk = chunk_r?;
+        let chunk = chunk_r?;
+        println!("size : {}", chunk.samples.len());
     }
 
     Ok(())