made resampler less slow

Author: davorinrusevljan

src/mediaUtils.ts

@@ -8,7 +8,8 @@ class ResamplerProcessor extends AudioWorkletProcessor {
     this.ratio = this.inputSampleRate / this.outputSampleRate;
     this.resampledBuffer = []; // Store resampled data to send to the main thread
     this.processCount = 0;  //Counter.
-    this.port.postMessage({ type: 'log', data: "constructor" }); 
+    this.pcmData = new Int16Array(8196);
+    this.pcmIndex = 0;
   }
 
   process(inputs, outputs, parameters) {
@@ -22,42 +23,44 @@ class ResamplerProcessor extends AudioWorkletProcessor {
     const inputChannel = input[0];
 
     // Resample the data
-    const resampledData = this.resample(inputChannel);
-    this.resampledBuffer = this.resampledBuffer.concat(Array.from(resampledData));
+    this.resample(inputChannel);
 
     this.processCount++; //Increment process count
     let messageRate = 100; //Message sent every 100 process calls.
     // Send the resampled data to the main thread (send in chunks)
-    if (this.processCount % messageRate === 0 && this.resampledBuffer.length > 0) {
-      //Limit what we send.
-      let sendCount = 8196;
-      let send = this.resampledBuffer.slice(0, sendCount);
-
-      this.port.postMessage({ type: 'resampledData', data: send });  //Send only part of the resampledBuffer;
-
-      //Purge the buffer.
-      this.resampledBuffer = this.resampledBuffer.slice(sendCount);
+    if (this.processCount % messageRate === 0 && this.pcmIndex > 0) {
+      // Convert Int16Array to a binary buffer (ArrayBuffer)
+      const pcmBuffer = new ArrayBuffer(this.pcmIndex * 2); // 2 bytes per sample
+      const pcmView = new DataView(pcmBuffer);
+      for (let i = 0; i < this.pcmIndex; i++) {
+        const pcmData_i = this.pcmData[i];
+        if (pcmData_i) {
+          pcmView.setInt16(i * 2, pcmData_i, true); // true means little-endian
+        }
+      }
+      this.port.postMessage({ type: 'resampledData', data: pcmBuffer }); 
+      this.pcmData = new Int16Array(8196);
+      this.pcmIndex = 0;
     }
 
     return true;
   }
 
   resample(inputChannel) {
-    const resampledData = [];
     let inputIndex = 0;
-
-    for (let outputIndex = 0; outputIndex < inputChannel.length / this.ratio; outputIndex++) {
+    const howMany = Math.floor(inputChannel.length / this.ratio)
+    let outputIndex;
+    for (outputIndex = 0; outputIndex < howMany; outputIndex++) {
       const inputIndexFloat = outputIndex * this.ratio;
       inputIndex = Math.floor(inputIndexFloat);
 
       if (inputIndex < inputChannel.length) {
-        resampledData.push(inputChannel[inputIndex]); // Replace with interpolation
+        this.pcmData[this.pcmIndex+outputIndex] = Math.max(-32768, Math.min(32767, inputChannel[inputIndex] * 32767));
       } else {
         break; //No more data, break out of loop
       }
     }
-
-    return resampledData;
+    this.pcmIndex += outputIndex;
   }
 }
 

src/soundWorklet.ts

@@ -180,11 +180,16 @@ export class WebRTC {
       resamplerNode.port.onmessage = (event) => {
         //console.log('Received message from resampler node', event);
         if (event.data.type === 'resampledData') {
-          const resampledData = event.data.data; //Get resampledData
-          console.log('Received resampled data len:', resampledData.length);
+          const audioData = event.data.data; //Get resampledData
+          console.log('Received resampled data len:', audioData.length);
+
+          const byteArray = new Uint8Array(audioData); // Create a Uint8Array view
+          const bufferString = String.fromCharCode(...byteArray); // convert each byte of the buffer to a character
+          const audioBase64String = btoa(bufferString); // Apply base64
+
           const audioMessage = {
             type: 'input_audio_buffer.delta',
-            delta: btoa(resampledData),
+            delta: btoa(audioBase64String),
           };
           if (this.connected && this.ws) {
             this.ws.send(JSON.stringify(audioMessage));