Improve audio interleaving (#100)

* Improve _interleave performance

* Fix indentation

src/crunker.ts

@@ -394,17 +394,24 @@ export default class Crunker {
    * @internal
    */
   private _interleave(input: AudioBuffer): Float32Array {
-    const channels = Array.from({ length: input.numberOfChannels }, (_, i) => i);
-    const length = channels.reduce((prev, channelIdx) => prev + input.getChannelData(channelIdx).length, 0);
+    if (input.numberOfChannels === 1) {
+      // No need to interleave channels, just return single channel data to save performance and memory
+      return input.getChannelData(0);
+    }
+    const channels = [];
+    for (let i = 0; i < input.numberOfChannels; i++) {
+      channels.push(input.getChannelData(i));
+    }
+    const length = channels.reduce((prev, channelData) => prev + channelData.length, 0);
     const result = new Float32Array(length);
 
     let index = 0;
     let inputIndex = 0;
 
     // for 2 channels its like: [L[0], R[0], L[1], R[1], ... , L[n], R[n]]
     while (index < length) {
-      channels.forEach((channelIdx) => {
-        result[index++] = input.getChannelData(channelIdx)[inputIndex];
+      channels.forEach((channelData) => {
+        result[index++] = channelData[inputIndex];
       });
 
       inputIndex++;