fix:增加音频解码、降噪

lib/talk/call/g711.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:math';
 import 'package:flutter/services.dart';
 
 class G711 {
@@ -20,6 +21,67 @@ class G711 {
     return (aVal & 0x80) != 0 ? 0x84 - t : t - 0x84;
   }
 
+  int decodeG711(int encodedValue, bool isALaw) {
+    if (isALaw) {
+      // A律解码
+      encodedValue = ~encodedValue;
+      int t = ((encodedValue & 0x0F) << 3) + 0x84;
+      t <<= (encodedValue & 0x70) >> 4;
+      return (encodedValue & 0x80) != 0 ? 0x84 - t : t - 0x84;
+    } else {
+      // μ律解码
+      encodedValue = ~encodedValue;
+      int t = ((encodedValue & 0x0F) << 3) + 0x84;
+      t <<= (encodedValue & 0x70) >> 4;
+      return (encodedValue & 0x80) != 0 ? 0x84 - t : t - 0x84;
+    }
+  }
+
+  /// 高通滤波
+  List<int> highPassFilter(
+      List<int> audioData, int sampleRate, double cutoffFreq) {
+    final double rc = 1.0 / (2 * pi * cutoffFreq);
+    final double dt = 1.0 / sampleRate;
+    final double alpha = rc / (rc + dt);
+
+    List<int> filteredData = [];
+    int prevInput = 0;
+    int prevOutput = 0;
+
+    for (int sample in audioData) {
+      int output = (alpha * (prevOutput + sample - prevInput)).round();
+      filteredData.add(output);
+      prevInput = sample;
+      prevOutput = output;
+    }
+
+    return filteredData;
+  }
+
+  /// 噪声门
+  List<int> noiseGate(List<int> audioData, int threshold) {
+    return audioData
+        .map((sample) => sample.abs() > threshold ? sample : 0)
+        .toList();
+  }
+
+  /// 解码并降噪
+  List<int> decodeAndDenoise(List<int> encodedData, bool isALaw, int sampleRate,
+      double cutoffFreq, int threshold) {
+    // 解码 G.711 数据
+    List<int> decodedData =
+        encodedData.map((value) => decodeG711(value, isALaw)).toList();
+
+    // 高通滤波
+    List<int> filteredData =
+        highPassFilter(decodedData, sampleRate, cutoffFreq);
+
+    // 噪声门
+    List<int> denoisedData = noiseGate(filteredData, threshold);
+
+    return denoisedData;
+  }
+
 //711解码为pcm数据
   List<int> convertList(List<int> aLawList) {
     // 将 ALawToLinear 函数应用于 List<int>