app-starlock/star_lock/lib/talk/call/g711Decoder.dart

import 'dart:typed_data';

enum G711Type {
  uLaw,
  aLaw,
}

class G711Decoder {
  Uint8List g711Decode(Uint8List g711Data, G711Type g711Type) {
    List<int> pcmData = [];
    int sign, exponent, mantissa, sample;

    for (int i = 0; i < g711Data.length; i++) {
      int value = g711Data[i];

      if (g711Type == G711Type.uLaw) {
        // μ-law decoding
        value = ~value & 0xFF;
        sign = (value & 0x80) == 0 ? 1 : -1;
        exponent = (value & 0x70) >> 4;
        mantissa = ((value & 0x0F) << 4) + 0x10;
        sample = (mantissa << exponent) * sign;
      } else {
        // A-law decoding
        sign = (value & 0x80) == 0 ? 1 : -1;
        exponent = ((value & 0x70) >> 4) + 1;
        mantissa = (value & 0x0F) + 0x10;
        sample = (mantissa << exponent) * sign;
      }

      pcmData.add(sample);
    }

    return Uint8List.fromList(pcmData);
  }
}