wehub-resource-sync
93 lines
3.0 KiB
JavaScript
93 lines
3.0 KiB
JavaScript
/**
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* Copyright 2026 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* An audio worklet processor that stores the PCM audio data sent from the main thread
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* to a buffer and plays it.
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*/
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class PCMPlayerProcessor extends AudioWorkletProcessor {
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constructor() {
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super();
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// Init buffer
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this.bufferSize = 24000 * 180; // 24kHz x 180 seconds
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this.buffer = new Float32Array(this.bufferSize);
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this.writeIndex = 0;
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this.readIndex = 0;
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// Handle incoming messages from main thread
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this.port.onmessage = (event) => {
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// Reset the buffer when 'endOfAudio' message received
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if (event.data.command === 'endOfAudio') {
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this.readIndex = this.writeIndex; // Clear the buffer
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console.log("endOfAudio received, clearing the buffer.");
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return;
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}
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// Decode the base64 data to int16 array.
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const int16Samples = new Int16Array(event.data);
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// Add the audio data to the buffer
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this._enqueue(int16Samples);
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};
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}
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// Push incoming Int16 data into our ring buffer.
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_enqueue(int16Samples) {
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for (let i = 0; i < int16Samples.length; i++) {
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// Convert 16-bit integer to float in [-1, 1]
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const floatVal = int16Samples[i] / 32768;
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// Store in ring buffer for left channel only (mono)
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this.buffer[this.writeIndex] = floatVal;
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this.writeIndex = (this.writeIndex + 1) % this.bufferSize;
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// Overflow handling (overwrite oldest samples)
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if (this.writeIndex === this.readIndex) {
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this.readIndex = (this.readIndex + 1) % this.bufferSize;
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}
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}
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}
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// The system calls `process()` ~128 samples at a time (depending on the browser).
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// We fill the output buffers from our ring buffer.
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process(inputs, outputs, parameters) {
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// Write a frame to the output
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const output = outputs[0];
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const framesPerBlock = output[0].length;
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for (let frame = 0; frame < framesPerBlock; frame++) {
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// Write the sample(s) into the output buffer
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output[0][frame] = this.buffer[this.readIndex]; // left channel
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if (output.length > 1) {
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output[1][frame] = this.buffer[this.readIndex]; // right channel
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}
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// Move the read index forward unless underflowing
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if (this.readIndex != this.writeIndex) {
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this.readIndex = (this.readIndex + 1) % this.bufferSize;
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}
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}
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// Returning true tells the system to keep the processor alive
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return true;
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}
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}
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registerProcessor('pcm-player-processor', PCMPlayerProcessor);
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