java实现一个视频的RTP头封装

以下是Java实现一个视频的RTP头封装的代码示例：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Random;

public class RTPPacket {
    private static final int RTP_HEADER_SIZE = 12;
    private static final int BUFFER_SIZE = 15000;
    private static final int PAYLOAD_TYPE = 96; // 96 is the default payload type for H.264 video

    private int seqNum;
    private int timestamp;
    private int ssrc;
    private byte[] payload;
    private int payloadSize;

    public RTPPacket(byte[] payload, int payloadSize) {
        this.payload = payload;
        this.payloadSize = payloadSize;
        // Initialize sequence number and timestamp randomly
        Random rand = new Random();
        seqNum = rand.nextInt(65535);
        timestamp = rand.nextInt(65535);
        // Initialize SSRC (synchronization source identifier) to a random value
        ssrc = rand.nextInt();
    }

    public void send(String destIP, int destPort, DatagramSocket socket) throws Exception {
        InetAddress destAddr = InetAddress.getByName(destIP);
        byte[] buffer = new byte[BUFFER_SIZE];
        buffer[0] = (byte) 0x80; // Version (2 bits) + Padding (1 bit) + Extension (1 bit) + CC (4 bits)
        buffer[1] = (byte) PAYLOAD_TYPE; // Payload Type (7 bits)
        buffer[2] = (byte) (seqNum >> 8); // Sequence Number (16 bits)
        buffer[3] = (byte) seqNum;
        buffer[4] = (byte) (timestamp >> 24); // Timestamp (32 bits)
        buffer[5] = (byte) (timestamp >> 16);
        buffer[6] = (byte) (timestamp >> 8);
        buffer[7] = (byte) timestamp;
        buffer[8] = (byte) (ssrc >> 24); // SSRC (32 bits)
        buffer[9] = (byte) (ssrc >> 16);
        buffer[10] = (byte) (ssrc >> 8);
        buffer[11] = (byte) ssrc;
        System.arraycopy(payload, 0, buffer, RTP_HEADER_SIZE, payloadSize);
        DatagramPacket packet = new DatagramPacket(buffer, RTP_HEADER_SIZE + payloadSize, destAddr, destPort);
        socket.send(packet);
    }
}

这个代码示例中的RTPPacket类表示一个RTP数据包。它的构造函数接受一个视频帧的字节数组payload和payload的大小payloadSize，将其存储为数据包的负载。每个RTP数据包都有一个序列号(seqNum)和一个时间戳(timestamp)，这些信息被初始化为随机值。SSRC是一个标识同步源的32位无符号整数，也被初始化为随机值。

send()方法将RTP数据包发送到指定的目标IP地址和端口号。它首先创建一个长度为BUFFER_SIZE的字节数组buffer，将RTP头的各个字段填充到buffer中，然后将payload复制到buffer的RTP头后面。最后，它创建一个DatagramPacket对象并将其发送到目标地址和端口号。