gb28181对g.711aRTP封装并发送

GB28181是一种基于SIP协议的视频监控标准，它使用RTP协议传输音视频数据。G.711a是一种音频编解码标准，可以将模拟信号转换成数字信号。在GB28181中，音频数据需要使用G.711a进行编码，并使用RTP协议进行封装和传输。

以下是使用C#语言实现GB28181对G.711a RTP封装并发送的示例代码：

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace GB28181_G711a_RTP
{
    class Program
    {
        static void Main(string[] args)
        {
            // 设置远程IP地址和端口号
            IPAddress remoteIP = IPAddress.Parse("192.168.1.100");
            int remotePort = 5000;

            // 创建UDP客户端
            UdpClient udpClient = new UdpClient();
            udpClient.Connect(remoteIP, remotePort);

            // 创建G.711a编码器
            GC711aEncoder encoder = new GC711aEncoder();

            // 读取音频数据
            byte[] audioData = ReadAudioData();

            // 将音频数据进行G.711a编码
            byte[] encodedData = encoder.Encode(audioData);

            // 创建RTP包
            RTPPacket packet = new RTPPacket();
            packet.Version = 2;
            packet.Padding = false;
            packet.Extension = false;
            packet.CSRCCount = 0;
            packet.Marker = false;
            packet.PayloadType = 0;
            packet.SequenceNumber = 0;
            packet.Timestamp = 0;
            packet.SSRC = 0;
            packet.PayloadData = encodedData;

            // 将RTP包转换成字节数组
            byte[] packetData = packet.ToBytes();

            // 发送RTP包
            udpClient.Send(packetData, packetData.Length);

            // 关闭UDP客户端
            udpClient.Close();
        }

        static byte[] ReadAudioData()
        {
            // 从麦克风或文件中读取音频数据
            // ...
        }
    }

    // G.711a编码器
    class GC711aEncoder
    {
        public byte[] Encode(byte[] data)
        {
            // 将模拟信号转换成数字信号
            short[] samples = new short[data.Length / 2];
            for (int i = 0; i < samples.Length; i++)
            {
                samples[i] = BitConverter.ToInt16(data, i * 2);
            }

            // 使用G.711a进行编码
            byte[] encodedData = new byte[samples.Length];
            for (int i = 0; i < samples.Length; i++)
            {
                encodedData[i] = MuLawEncoder.LinearToMuLawSample(samples[i]);
            }

            return encodedData;
        }
    }

    // RTP包
    class RTPPacket
    {
        public int Version { get; set; }
        public bool Padding { get; set; }
        public bool Extension { get; set; }
        public int CSRCCount { get; set; }
        public bool Marker { get; set; }
        public int PayloadType { get; set; }
        public int SequenceNumber { get; set; }
        public uint Timestamp { get; set; }
        public uint SSRC { get; set; }
        public byte[] PayloadData { get; set; }

        public byte[] ToBytes()
        {
            byte[] data = new byte[12 + PayloadData.Length];
            data[0] = (byte)((Version << 6) | (Padding ? 0x20 : 0x00) | (Extension ? 0x10 : 0x00) | CSRCCount);
            data[1] = (byte)((Marker ? 0x80 : 0x00) | PayloadType);
            data[2] = (byte)(SequenceNumber >> 8);
            data[3] = (byte)SequenceNumber;
            data[4] = (byte)(Timestamp >> 24);
            data[5] = (byte)(Timestamp >> 16);
            data[6] = (byte)(Timestamp >> 8);
            data[7] = (byte)Timestamp;
            data[8] = (byte)(SSRC >> 24);
            data[9] = (byte)(SSRC >> 16);
            data[10] = (byte)(SSRC >> 8);
            data[11] = (byte)SSRC;
            Array.Copy(PayloadData, 0, data, 12, PayloadData.Length);
            return data;
        }
    }

    // G.711a Mu-law 编码器
    static class MuLawEncoder
    {
        public const int Mu = 255;
        public const int MuLawBias = 132;

        public static byte LinearToMuLawSample(short sample)
        {
            int sign = (sample >> 8) & 0x80;
            if (sign != 0)
            {
                sample = (short)-sample;
            }
            if (sample > Mu)
            {
                sample = Mu;
            }
            sample += MuLawBias;
            int exponent = (int)Math.Log(sample, 2);
            int mantissa = sample >> (exponent + 3);
            int index = (exponent << 4) | mantissa;
            if (sign != 0)
            {
                index = ~index;
            }
            return (byte)index;
        }
    }
}

上述示例代码中，首先创建UDP客户端，并设置远程IP地址和端口号。然后创建G.711a编码器，读取音频数据，并将音频数据进行G.711a编码。接着创建RTP包，并将G.711a编码后的数据作为RTP包的负载数据。最后将RTP包转换成字节数组，并使用UDP客户端发送到远程主机。

需要注意的是，以上示例代码只是一个简单的示例，实际应用中需要考虑更多的因素，例如网络延迟、丢包等问题。