8 files changed, 171 insertions, 0 deletions
diff --git a/normalizer/normalizer.html b/normalizer/normalizer.html
new file mode 100755
index 0000000..d166c65
--- /dev/null
+++ b/normalizer/normalizer.html
@@ -0,0 +1,171 @@
+<script type="text/javascript">
+</script>
+<table>
+
+<tr>
+<th>
+Not normalized
+</th>
+<th>
+Normalized
+</th>
+<th>
+Computed gain
+</th>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-a.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-a-n" controls> <source src="sample-a.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-a-d"></div>
+</td>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-b.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-b-n" controls> <source src="sample-b.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-b-d"></div>
+</td>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-c.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-c-n" controls> <source src="sample-c.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-c-d"></div>
+</td>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-d.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-d-n" controls> <source src="sample-d.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-d-d"></div>
+</td>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-e.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-e-n" controls> <source src="sample-e.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-e-d"></div>
+</td>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-f.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-f-n" controls> <source src="sample-f.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-f-d"></div>
+</td>
+</tr>
+
+<tr>
+<td>
+<audio controls> <source src="sample-g.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<audio id="sample-g-n" controls> <source src="sample-g.mp3" type="audio/mpeg">Audio element not supported</audio>
+</td>
+<td>
+<div id="sample-g-d"></div>
+</td>
+</tr>
+
+</table>
+<script type="text/javascript">
+    function start() {
+        var audioCtx = new AudioContext();
+
+// http://wiki.hydrogenaud.io/index.php?title=ReplayGain_specification
+// TODO: do the loudness filtering (Butterworth, Yulewalk) IIR filters
+
+        function normalizedAudioElement(name) {
+            var audioElem = document.getElementById(name + "-n");
+            var src = audioCtx.createMediaElementSource(audioElem);
+            var gainNode = audioCtx.createGain();
+            gainNode.gain.value = 1.0;
+
+            audioElem.addEventListener("play", function() {
+                src.connect(gainNode);
+                gainNode.connect(audioCtx.destination);
+            }, true);
+            audioElem.addEventListener("pause", function() {
+                // disconnect the nodes on pause, otherwise all nodes always run
+                src.disconnect(gainNode);
+                gainNode.disconnect(audioCtx.destination);
+            }, true);
+            fetch(name + ".mp3")
+                .then(function(res) { return res.arrayBuffer(); })
+                .then(function(buf) {
+                    return audioCtx.decodeAudioData(buf);
+                }).then(function(decodedData) {
+                var decodedBuffer = decodedData.getChannelData(0);
+                var sliceLen = Math.floor(decodedData.sampleRate * 0.05);
+                var averages = [];
+                var sum = 0.0;
+                for (var i = 0; i < decodedBuffer.length; i++) {
+                    sum += decodedBuffer[i] ** 2;
+                    if (i % sliceLen === 0) {
+                        sum = Math.sqrt(sum / sliceLen);
+                        averages.push(sum);
+                        sum = 0;
+                    }
+                }
+                // Ascending sort of the averages array
+                averages.sort(function(a, b) { return a - b; });
+                // Take the average at the 95th percentile
+                var a = averages[Math.floor(averages.length * 0.95)];
+
+                var gain = 1.0 / a;
+                // Perform some clamping
+                // gain = Math.max(gain, 0.02);
+                // gain = Math.min(gain, 100.0);
+
+                // ReplayGain uses pink noise for this one one but we just take
+                // some arbitrary value... we're no standard
+                // Important is only that we don't output on levels
+                // too different from other websites
+                gain = gain / 10.0;
+                console.log("gain determined", name, a, gain);
+                gainNode.gain.value = gain;
+                var gainTextElem = document.getElementById(name + "-d");
+                gainTextElem.textContent = gain.toPrecision(4);
+            });
+        }
+
+        normalizedAudioElement("sample-a");
+        normalizedAudioElement("sample-b");
+        normalizedAudioElement("sample-c");
+        normalizedAudioElement("sample-d");
+        normalizedAudioElement("sample-e");
+        normalizedAudioElement("sample-f");
+        normalizedAudioElement("sample-g");
+    }
+</script>
diff --git a/normalizer/sample-a.mp3 b/normalizer/sample-a.mp3
new file mode 100755
index 0000000..6b6041e
--- /dev/null
+++ b/normalizer/sample-a.mp3
diff --git a/normalizer/sample-b.mp3 b/normalizer/sample-b.mp3
new file mode 100755
index 0000000..bb8c766
--- /dev/null
+++ b/normalizer/sample-b.mp3
diff --git a/normalizer/sample-c.mp3 b/normalizer/sample-c.mp3
new file mode 100755
index 0000000..bc488f1
--- /dev/null
+++ b/normalizer/sample-c.mp3
diff --git a/normalizer/sample-d.mp3 b/normalizer/sample-d.mp3
new file mode 100755
index 0000000..b51df1c
--- /dev/null
+++ b/normalizer/sample-d.mp3
diff --git a/normalizer/sample-e.mp3 b/normalizer/sample-e.mp3
new file mode 100755
index 0000000..85ef615
--- /dev/null
+++ b/normalizer/sample-e.mp3
diff --git a/normalizer/sample-f.mp3 b/normalizer/sample-f.mp3
new file mode 100755
index 0000000..17e5e96
--- /dev/null
+++ b/normalizer/sample-f.mp3
diff --git a/normalizer/sample-g.mp3 b/normalizer/sample-g.mp3
new file mode 100755
index 0000000..e610b33
--- /dev/null
+++ b/normalizer/sample-g.mp3