fix: 降采样到16k

src/index.tsx

@@ -484,15 +484,20 @@ export function Home() {
    * @param u8 - 双声道PCM数据
    * @returns - 左声道RMS，右声道RMS，单声道PCM数据
    */
-  const rms = (u8: Uint8Array): [number, number, Int8Array] => {
-    if (!u8 || u8.byteLength <= 8) return [0, 0, new Int8Array(0)];
-    const frameCount = Math.floor((u8.length - 8) / 4); // 每帧: L(2B)+R(2B)
-    if (frameCount <= 0) return [0, 0, new Int8Array(0)];
+  const rms = (u8: Uint8Array): [number, number, Uint8Array] => {
+    if (!u8 || u8.byteLength <= 8) return [0, 0, new Uint8Array(0)];
+    // 每帧: L(2B)+R(2B)，总帧数（48k立体声）
+    const totalFrames = Math.floor((u8.length - 8) / 4);
+    if (totalFrames <= 0) return [0, 0, new Uint8Array(0)];
+    // 48k -> 16k，降采样因子为3
+    const downFactor = 3;
+    const outFrames = Math.floor((totalFrames + downFactor - 1) / downFactor) * 2; // 向上取整
     let sumL = 0;
     let sumR = 0;
-    const mono8 = new Int8Array(frameCount);
-    let j = 0;
-    for (let i = 8; i + 3 < u8.length; i += 4, j++) {
+    const mono8 = new Uint8Array(outFrames);
+    let j = 0, k = 0;
+    for (let i = 8; i + 3 < u8.length; i += 4, j++)
+    {
       const a = u8[i + 0] & 0xff;
       const b = u8[i + 1] & 0xff;
       const c = u8[i + 2] & 0xff;
@@ -509,16 +514,20 @@ export function Home() {
       sumR += nr * nr;
       // 双声道合成为单声道（16-bit），再压缩为 Int8
       // C = A + B - (A * B / 32767)
-      let m = l + r - Math.floor((l * r) / 32767);
-      if (m > 32767) m = 32767;
-      else if (m < -32768) m = -32768;
-      let m8 = m >> 8; // 16-bit 转 8-bit（有符号算术右移）
-      if (m8 > 127) m8 = 127;
-      else if (m8 < -128) m8 = -128;
-      mono8[j] = m8;
+      if (j % downFactor == 0)
+      {
+        let m = l + r - Math.floor((l * r) / 32767);
+        if (m > 32767) m = 32767;
+        else if (m < -32768) m = -32768;
+        let H = (m >> 8) & 0xff;
+        let L = m & 0xff;
+        mono8[k++] = (L << 8);
+        mono8[k++] = H;
+      }
     }
-    const leftRms = Math.sqrt(sumL / frameCount);
-    const rightRms = Math.sqrt(sumR / frameCount);
+    const leftRms = Math.sqrt(sumL / totalFrames);
+    const rightRms = Math.sqrt(sumR / totalFrames);
+    // 返回实际长度的视图，避免尾部未填充元素
     return [leftRms, rightRms, mono8];
   }
 
@@ -531,8 +540,10 @@ export function Home() {
     if (live?.data == null) return;
     setLiveStates('live: ' + live.data.length + ' rest: ' + live.rest + ' muted: ' + live.muted);
     // 仅计算，不保留引用；如需录音导出再使用 blocksRef.current.push(live.data.slice(8))
-    blocksRef.current.push(live.data.slice(8));
-    const [rms1, rms2] = rms(live.data);
+    // blocksRef.current.push(live.data.slice(8));
+    const [rms1, rms2, mono16k] = rms(live.data);
+    // 基于切片内容复制，避免使用 .buffer 造成长度/偏移误用
+    blocksRef.current.push(new Uint8Array(mono16k));
     // console.log('live, rms1', rms1, 'rms2', rms2);
     setRmsLeft(Math.floor(rms1 * 4 * 400));
     setRmsRight(Math.floor(rms2 * 4 * 400));
@@ -550,7 +561,7 @@ export function Home() {
       window.clearTimeout(liveTimeoutRef.current);
     }
     // 立即触发一次，并在回调末尾调度下一次
-    scheduleLiveTick();
+    liveTimeoutRef.current = window.setTimeout(scheduleLiveTick, 100);
   }
   
   const stopLive = async () => {
@@ -563,63 +574,22 @@ export function Home() {
       liveTimeoutRef.current = null;
     }
     console.log('live stopped');
-    // 将blocks拼接成一个Uint8Array，并下载到本地
-    // 将blocksRef.current的双声道PCM合并为单声道
-    // 每个块都是(interleaved) 2通道，每个通道16bit(2字节)，小端
-    // 合并算法: C = A + B - (A * B / 32767)
-    let monoChunks: Int16Array[] = [];
-    for (const block of blocksRef.current) {
-      // 每帧4字节: L(2字节) R(2字节)
-      let view = new DataView(block.buffer, block.byteOffset, block.byteLength);
-      let sampleCount = block.length / 4;
-      let mono = new Int16Array(sampleCount);
-      for (let i = 0; i < sampleCount; ++i) {
-        let offset = i * 4;
-        let l = view.getInt16(offset, true);
-        let r = view.getInt16(offset + 2, true);
-        // C = A + B - (A * B / 32767)
-        let c = l + r - Math.floor((l * r) / 32767);
-        // 限定在16bit
-        if (c > 32767) c = 32767;
-        if (c < -32768) c = -32768;
-        mono[i] = c;
-      }
-      monoChunks.push(mono);
-    }
-    // 合并所有Int16Array为单一Int16Array
-    const totalSamples = monoChunks.reduce((sum, arr) => sum + arr.length, 0);
-    const monoAll = new Int16Array(totalSamples);
+    
+    // 将blocksRef.current合并为单一Uint8Array
+    const totalSamples = blocksRef.current.reduce((sum, arr) => sum + arr.length, 0);
+    const monoAll = new Uint8Array(totalSamples);
     let offsetMono = 0;
-    for (const arr of monoChunks) {
+    for (const arr of blocksRef.current) {
       monoAll.set(arr, offsetMono);
       offsetMono += arr.length;
     }
-    // e.g. 可导出为 .pcm 文件
-    let monoBlob = new Blob([monoAll.buffer], { type: 'audio/pcm' });
-    let monoUrl = URL.createObjectURL(monoBlob);
-    let monoA = document.createElement('a');
-    monoA.href = monoUrl;
-    monoA.download = 'live_mono.pcm';
-    monoA.click();
-    URL.revokeObjectURL(monoUrl);
-    /*
-    const totalLen = blocksRef.current.reduce((sum, b) => sum + b.length, 0);
-    const data = new Uint8Array(totalLen);
-    let offset = 0;
-    for (const b of blocksRef.current) {
-      data.set(b, offset);
-      offset += b.length;
-    }
-    // 清空缓存
-    blocksRef.current = [];
-    let blob = new Blob([data], { type: 'audio/pcm' });
+    let blob = new Blob([monoAll.buffer], { type: 'audio/pcm' });
     let url = URL.createObjectURL(blob);
     let a = document.createElement('a');
     a.href = url;
     a.download = 'live.pcm';
     a.click();
     URL.revokeObjectURL(url);
-    */
   }
 
   return (