From ce8514cc39557000fbf0d82a6bef31b4741b7313 Mon Sep 17 00:00:00 2001
From: Paul <paul.pei@sparticle.com>
Date: Tue, 4 Jun 2024 11:25:14 +0800
Subject: [PATCH] =?UTF-8?q?Feat:=20floatTo16BitPCM=20=E8=BD=AC=E6=8D=A2?=
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---
 src/App.tsx        |  4 ++--
 src/utils/audio.ts | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/App.tsx b/src/App.tsx
index 8bfe50c..eb0ae67 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -4,7 +4,7 @@ import viteLogo from "/vite.svg";
 import "./App.css";
 import { client, start } from "./utils/mqtt";
 import { startAudio, stopAudio, context } from "./utils/microphone";
-import { arrayBufferToBase64, downSampleAudioFrame, getMergedPCMData } from "./utils/audio";
+import { arrayBufferToBase64, downSampleAudioFrame, floatTo16BitPCM, getMergedPCMData } from "./utils/audio";
 
 let mqttData;
 
@@ -17,7 +17,7 @@ const getAudio = () => {
     // 降比特率到 16000
     const downedFloat32Arr = downSampleAudioFrame(float32Arr, context.sampleRate, 16000);
     // 转 base64 打包给后端
-    const sendItem = arrayBufferToBase64(downedFloat32Arr.buffer);
+    const sendItem = arrayBufferToBase64(floatTo16BitPCM(downedFloat32Arr));
     // 存储一遍压缩后的音频
     buffers.push(downedFloat32Arr);
 
diff --git a/src/utils/audio.ts b/src/utils/audio.ts
index 1117717..5060579 100644
--- a/src/utils/audio.ts
+++ b/src/utils/audio.ts
@@ -61,3 +61,22 @@ export const arrayBufferToBase64 = (buffer: ArrayBuffer) => {
   }
   return window.btoa(binary);
 }
+
+// Float32 转 16 Bit PCM
+export const floatTo16BitPCM = (input: Float32Array) => {
+  const audioLength = input.length * 2;
+
+  // 新开一个对象
+  const buffer = new ArrayBuffer(audioLength);
+  const view = new DataView(buffer);
+
+  // 写入 input 的数据到 buffer 里面（view 理解成只是一个操作手段）
+  let offset = 0;
+
+  for (let i = 0; i < input.length; i++ , offset += 2) {
+    const s = Math.max(-1, Math.min(1, input[i]));
+    view.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
+  }
+
+  return buffer;
+}