Adding RFFT example.

corbanbrook · corbanbrook · commit 625eb5488c87 · 2011-03-01T10:23:38.000-05:00
diff --git a/examples/rfft.html b/examples/rfft.html
@@ -0,0 +1,84 @@
+<html>
+  <head>      
+    <script language="javascript" src="js/processing.js"></script>
+    <script language="javascript" src="js/init.js"></script>
+    <script language="javascript" src="../dsp.js"></script>
+  </head>
+  <body>
+    <style>
+      body { background: black; margin:0; padding:0;}
+    </style>
+    
+    <script>
+      var frameBufferSize = 4096;
+      var bufferSize = frameBufferSize/2;
+      
+      var signal = new Float32Array(bufferSize);
+      var peak = new Float32Array(bufferSize);
+      
+      var fft = new RFFT(bufferSize, 44100);
+
+      function loadedMetaData(event) {
+        var audio = document.getElementById('input');
+        audio.mozFrameBufferLength = frameBufferSize;
+        audio.addEventListener("MozAudioAvailable", audioAvailable, false);
+      }
+
+      function audioAvailable(event) {
+        // deinterleave and mix down to mono
+        signal = DSP.getChannel(DSP.MIX, event.frameBuffer);
+
+        // perform forward transform
+        fft.forward(signal);
+        
+        // calculate peak values
+        for ( var i = 0; i < bufferSize; i++ ) {
+          fft.spectrum[i] *= -1 * Math.log((fft.bufferSize/2 - i) * (0.5/fft.bufferSize/2)) * fft.bufferSize; // equalize, attenuates low freqs and boosts highs
+          
+          if ( peak[i] < fft.spectrum[i] ) {
+            peak[i] = fft.spectrum[i];
+          } else {
+            peak[i] *= 0.99; // peak slowly falls until a new peak is found
+          }
+        }
+      }
+    </script>
+    
+    <script target="#fft" type="application/processing">
+      void setup() {
+        size(1400, 600);
+        colorMode(HSB, 360, 100, 100);
+        strokeWeight(3);
+        frameRate(60);
+        //strokeCap(SQUARE);
+      }
+      
+      void draw() {
+        background(0);
+        //fill(0, 60);
+        //rect(0, 0, width, height);
+        for ( int i = 0; i < fft.spectrum.length/2; i += 3 ) {          
+          if (3 * i > width) { break; }
+          var magnitude = fft.spectrum[i];
+          
+          // draw magnitudes
+          stroke((i) % 360, 60, constrain(magnitude * 6, 20, 100));
+          line(3*i, height, 3*i, height - magnitude * 16);
+          
+          // draw peak indicators
+          stroke((i) % 360, 60, constrain(magnitude * 100, 50, 100));
+          line(3*i, height - peak[i] * 16 - 1, 3*i, height - peak[i] * 16);
+        }
+        /*
+        if (frameCount % 100 == 0 ) {
+          println(FRAME_RATE);
+        }
+        */
+      } 
+    </script>
+    
+    <audio id="input" src="audio/corban-peddle.ogg" controls="true" onloadedmetadata="loadedMetaData(event);"></audio><br />
+    
+    <div><canvas id="fft"></canvas></div>
+  </body>
+</html>
