133 lines
3.8 KiB
Dart
Executable File
133 lines
3.8 KiB
Dart
Executable File
import 'dart:async';
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import 'dart:math';
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import 'package:flutter/services.dart';
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class G711 {
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Future<List<int>> readAssetFile(String assetPath) async {
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final ByteData data = await rootBundle.load(assetPath);
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final List<int> bytes = data.buffer.asUint8List();
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return bytes;
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}
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int ALawToLinear(int aVal) {
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// 取反
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aVal = ~aVal;
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// 计算偏移
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int t = ((aVal & 0x0F) << 3) + 0x84;
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t <<= (aVal & 0x70) >> 4;
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// 根据符号位决定返回值的正负
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return (aVal & 0x80) != 0 ? 0x84 - t : t - 0x84;
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}
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int decodeG711(int encodedValue, bool isALaw) {
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if (isALaw) {
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// A律解码
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encodedValue ^= 0x55; // 反转最高位
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int sign = encodedValue & 0x80; // 符号位
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int exponent = (encodedValue & 0x70) >> 4; // 指数位
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int mantissa = encodedValue & 0x0F; // 尾数位
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int pcmSample = (mantissa << 4) + 0x84; // 计算量化值
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pcmSample <<= exponent; // 根据指数位移位
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pcmSample = (sign == 0) ? pcmSample : -pcmSample; // 处理符号位
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return pcmSample;
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} else {
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// μ律解码
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encodedValue ^= 0xFF; // 反转最高位
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int sign = encodedValue & 0x80; // 符号位
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int exponent = (encodedValue & 0x70) >> 4; // 指数位
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int mantissa = encodedValue & 0x0F; // 尾数位
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int pcmSample = (mantissa << 3) + 0x84; // 计算量化值
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pcmSample <<= exponent + 1; // 根据指数位移位（μ律需要额外加1）
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pcmSample = (sign == 0) ? pcmSample : -pcmSample; // 处理符号位
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return pcmSample;
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}
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}
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/// 高通滤波
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List<int> highPassFilter(
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List<int> audioData, int sampleRate, double cutoffFreq) {
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final double rc = 1.0 / (2 * pi * cutoffFreq);
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final double dt = 1.0 / sampleRate;
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final double alpha = rc / (rc + dt);
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List<int> filteredData = [];
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int prevInput = 0;
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int prevOutput = 0;
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for (int sample in audioData) {
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int output = (alpha * (prevOutput + sample - prevInput)).round();
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filteredData.add(output);
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prevInput = sample;
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prevOutput = output;
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}
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return filteredData;
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}
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/// 噪声门
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List<int> noiseGate(List<int> audioData, int threshold) {
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return audioData
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.map((sample) => sample.abs() > threshold ? sample : 0)
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.toList();
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}
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List<int> removeEcho(List<int> audioData, int delaySamples, double decay) {
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final List<int> processedData = [];
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for (int i = 0; i < audioData.length; i++) {
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int sample = audioData[i];
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if (i >= delaySamples) {
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sample -= (audioData[i - delaySamples] * decay).round();
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}
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processedData.add(sample);
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}
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return processedData;
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}
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/// 解码并降噪
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List<int> decodeAndDenoise(List<int> encodedData, bool isALaw, int sampleRate,
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double cutoffFreq, int threshold) {
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// 解码 G.711 数据
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List<int> decodedData =
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encodedData.map((value) => decodeG711(value, isALaw)).toList();
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// 高通滤波
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List<int> filteredData =
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highPassFilter(decodedData, sampleRate, cutoffFreq);
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// 噪声门
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List<int> denoisedData = noiseGate(filteredData, threshold);
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// 回声消除处理
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final List<int> processedData = removeEcho(denoisedData, 160, 0.5);
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return processedData;
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}
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//711解码为pcm数据
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List<int> convertList(List<int> aLawList) {
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// 将 ALawToLinear 函数应用于 List<int>
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final List<int> linearList = aLawList.map(ALawToLinear).toList();
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return linearList;
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}
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//List<int>转为Uint8List
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Uint8List convertToInt8ListLittleEndian(List<int> intList) {
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final List<int> int8List = [];
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for (int intValue in intList) {
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intValue = intValue * 2;
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// 将 int 拆分为两个字节，采用小端序
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int8List.add(intValue & 0xFF); // 低 8 位
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int8List.add((intValue & 0xFF00) >> 8); // 高 8 位
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}
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return Uint8List.fromList(int8List);
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}
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}
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