110 lines
3.1 KiB
JavaScript
110 lines
3.1 KiB
JavaScript
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/**
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* PCM 流式播放 AudioWorklet Processor
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* 动态扩容缓冲区 + 线性插值重采样（24kHz PCM → 系统采样率）
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* 豆包 TTS PCM 格式：24000Hz / 16bit / mono / little-endian (pcm_s16le)
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*/
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class PcmPlaybackProcessor extends AudioWorkletProcessor {
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constructor() {
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super();
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// 缓冲区：初始 60 秒 @ 24kHz = 1440000 采样，足够容纳 TTS 突发数据
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this._bufferSize = 1440000;
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this._buffer = new Float32Array(this._bufferSize);
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this._writePos = 0;
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this._readPos = 0;
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this._stopped = false;
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// 重采样：从 24kHz 到系统采样率（sampleRate 是 AudioWorklet 全局变量）
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this._srcRate = 24000;
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this._ratio = this._srcRate / sampleRate;
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this._fractionalPos = 0;
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this.port.onmessage = (e) => {
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const { type } = e.data;
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if (type === 'pcm') {
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this._enqueuePcm(e.data.buffer);
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} else if (type === 'clear') {
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this._writePos = 0;
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this._readPos = 0;
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this._fractionalPos = 0;
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} else if (type === 'stop') {
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this._stopped = true;
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}
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};
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}
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/** 缓冲区中可读采样数 */
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_available() {
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const diff = this._writePos - this._readPos;
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return diff >= 0 ? diff : diff + this._bufferSize;
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}
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/** 将 Int16 PCM 数据转为 Float32 写入缓冲区，空间不足时自动扩容 */
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_enqueuePcm(arrayBuffer) {
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const int16 = new Int16Array(arrayBuffer);
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const len = int16.length;
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const avail = this._available();
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// 如果剩余空间不够，扩容到当前 2 倍
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if (avail + len >= this._bufferSize - 1) {
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this._grow(Math.max(this._bufferSize * 2, avail + len + this._bufferSize));
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}
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for (let i = 0; i < len; i++) {
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this._buffer[this._writePos] = int16[i] / 32768;
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this._writePos = (this._writePos + 1) % this._bufferSize;
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}
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}
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/** 扩容缓冲区，保留已有数据 */
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_grow(newSize) {
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const newBuf = new Float32Array(newSize);
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const avail = this._available();
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// 按顺序拷贝可读数据到新缓冲区头部
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for (let i = 0; i < avail; i++) {
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newBuf[i] = this._buffer[(this._readPos + i) % this._bufferSize];
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}
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this._buffer = newBuf;
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this._bufferSize = newSize;
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this._readPos = 0;
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this._writePos = avail;
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}
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process(inputs, outputs) {
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if (this._stopped) return false;
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const output = outputs[0][0];
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if (!output) return true;
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for (let i = 0; i < output.length; i++) {
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// 需要至少 2 个采样做线性插值
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if (this._available() < 2) {
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output[i] = 0;
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continue;
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}
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// 线性插值重采样
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const intPart = Math.floor(this._fractionalPos);
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const frac = this._fractionalPos - intPart;
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const idx0 = (this._readPos + intPart) % this._bufferSize;
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const idx1 = (this._readPos + intPart + 1) % this._bufferSize;
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output[i] = this._buffer[idx0] + (this._buffer[idx1] - this._buffer[idx0]) * frac;
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// 步进
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this._fractionalPos += this._ratio;
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// 消费已经越过的整数采样
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const consumed = Math.floor(this._fractionalPos);
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if (consumed > 0) {
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this._readPos = (this._readPos + consumed) % this._bufferSize;
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this._fractionalPos -= consumed;
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}
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}
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return true;
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}
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}
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registerProcessor('pcm-playback-processor', PcmPlaybackProcessor);
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