6、多播传输RTP包
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2022-03-17 14:47:45
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一、多播
1.1 多播简介
单播地址标识当个IP接口，广播地址标识某个子网的所有IP接口，多播地址标识一组IP接口
单播和多播是两个极端，多播则在这两者之间折衷
多播数据报只由加入多播组的应用的主机的接口接收
IPV4的D类地址是IPV4的多播地址，范围是（224.0.0.0-239.255.255.255）
下面这张图对多播地址进行细分
1.2 多播示例
下面讲解一下多播的客户端与服务端编程
-
服务端
多播服务端并不需要什么特殊的操作，只需要创建udp套接字，然后向多播地址指定端口发送数据就行
-
客户端
多播客户端需要做的工作是，创建udp套接字，绑定多播端口，加入多播组
下面是示例代码
-
服务端
/*
*broadcast_server.c - 多播服务程序
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#define MCAST_PORT 8888
#define MCAST_ADDR "239.255.255.11"
#define MCAST_DATA "BROADCAST TEST DATA" /*多播发送的数据*/
#define MCAST_INTERVAL 1 /*发送间隔时间*/
int main(int argc, char*argv)
{
struct sockaddr_in mcast_addr;
int fd = socket(AF_INET, SOCK_DGRAM, 0); /*建立套接字*/
if (fd == -1)
{
perror("socket()");
exit(1);
}
memset(&mcast_addr, 0, sizeof(mcast_addr));/*初始化IP多播地址为0*/
mcast_addr.sin_family = AF_INET; /*设置协议族类行为AF*/
mcast_addr.sin_addr.s_addr = inet_addr(MCAST_ADDR);/*设置多播IP地址*/
mcast_addr.sin_port = htons(MCAST_PORT); /*设置多播端口*/
/*向多播地址发送数据*/
while(1)
{
int n = sendto(fd,MCAST_DATA,sizeof(MCAST_DATA),0,(struct sockaddr*)&mcast_addr,sizeof(mcast_addr)) ;
if( n < 0)
{
perror("sendto()");
exit(1);
}
sleep(MCAST_INTERVAL); /*等待一段时间*/
}
return 0;
}
客户端
/*
*broadcast_client.c - 多播的客户端
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#define MCAST_PORT 8888
#define MCAST_ADDR "239.255.255.11"
#define MCAST_INTERVAL 1 /*发送间隔时间*/
#define BUFF_SIZE 256 /*接收缓冲区大小*/
int main(int argc, char*argv[])
{
struct sockaddr_in local_addr; /*本地地址*/
int fd = socket(AF_INET, SOCK_DGRAM, 0); /*建立套接字*/
if (fd == -1)
{
perror("socket()");
exit(1);
}
int yes = 1;
if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) < 0)
{
perror("Reusing ADDR failed");
exit(1);
}
/*初始化本地地址*/
memset(&local_addr, 0, sizeof(local_addr));
local_addr.sin_family = AF_INET;
local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
local_addr.sin_port = htons(MCAST_PORT);
/*绑定socket*/
int err = bind(fd,(struct sockaddr*)&local_addr, sizeof(local_addr)) ;
if(err < 0)
{
perror("bind()");
exit(1);
}
/*设置回环许可*/
int loop = 1;
err = setsockopt(fd,IPPROTO_IP, IP_MULTICAST_LOOP,&loop, sizeof(loop));
if(err < 0)
{
perror("setsockopt():IP_MULTICAST_LOOP");
exit(1);
}
/*加入多播组*/
struct ip_mreq mreq;
mreq.imr_multiaddr.s_addr = inet_addr(MCAST_ADDR); /*多播地址*/
mreq.imr_interface.s_addr = htonl(INADDR_ANY); /*本地网络接口为默认*/
/*将本机加入多播组*/
err = setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,&mreq, sizeof(mreq));
if (err < 0)
{
perror("setsockopt():IP_ADD_MEMBERSHIP");
exit(1);
}
int times = 0;
int addr_len = sizeof(local_addr);
char buff[BUFF_SIZE];
int n = 0;
/*循环接收多播组的消息，5次后退出*/
for(times = 0;times < 5;times++)
{
memset(buff, 0, BUFF_SIZE); /*清空接收缓冲区*/
/*接收数据*/
n = recvfrom(fd, buff, BUFF_SIZE, 0,(struct sockaddr*)&local_addr,&addr_len);
if( n== -1)
{
perror("recvfrom()");
}
/*打印信息*/
printf("Recv %dst message from server:%s\n", times, buff);
sleep(MCAST_INTERVAL);
}
/*退出多播组*/
err = setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP,&mreq, sizeof(mreq));
close(fd);
return 0;
}
需要好好看一看这个示例，了解多播编程的流程
二、多播的sdp描述文件
m=video 9832 RTP/AVP 96
c=IN IP4 239.255.255.11/255
a=rtpmap:96 H264/90000
a=framerate:25
这是一个多播H.264的sdp文件
相关的讲解前面已经讲了很多了
这里需要注意的是目的端口号为9832，多播IP为239.255.255.11
三、多播传输RTP包实现
3.1 实现
对于我们来说，我们实现的是服务端，所以非常简单，无需过多操作，只需要把从零开始写一个RTSP服务器（三）RTP传输H.264中的目的IP和目的端口改为目的多播IP和目的多播端口就行
关于RTP打包这里不再重复，前面已经讲解得非常详细了
3.2 源码
multicast.c
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include "rtp.h"
#define H264_FILE_NAME "test.h264"
#define MULTICAST_IP "239.255.255.11"
#define MULTICAST_PORT 9832
#define FPS 25
static inline int startCode3(char* buf)
{
if(buf[0] == 0 && buf[1] == 0 && buf[2] == 1)
return 1;
else
return 0;
}
static inline int startCode4(char* buf)
{
if(buf[0] == 0 && buf[1] == 0 && buf[2] == 0 && buf[3] == 1)
return 1;
else
return 0;
}
static char* findNextStartCode(char* buf, int len)
{
int i;
if(len < 3)
return NULL;
for(i = 0; i < len-3; ++i)
{
if(startCode3(buf) || startCode4(buf))
return buf;
++buf;
}
if(startCode3(buf))
return buf;
return NULL;
}
static int getFrameFromH264File(int fd, char* frame, int size)
{
int rSize, frameSize;
char* nextStartCode;
if(fd < 0)
return fd;
rSize = read(fd, frame, size);
if(!startCode3(frame) && !startCode4(frame))
return -1;
nextStartCode = findNextStartCode(frame+3, rSize-3);
if(!nextStartCode)
{
lseek(fd, 0, SEEK_SET);
frameSize = rSize;
}
else
{
frameSize = (nextStartCode-frame);
lseek(fd, frameSize-rSize, SEEK_CUR);
}
return frameSize;
}
static int createUdpSocket()
{
int fd;
int on = 1;
fd = socket(AF_INET, SOCK_DGRAM, 0);
if(fd < 0)
return -1;
setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (const char*)&on, sizeof(on));
return fd;
}
static int rtpSendH264Frame(int socket, char* ip, int16_t port,
struct RtpPacket* rtpPacket, uint8_t* frame, uint32_t frameSize)
{
uint8_t naluType; // nalu第一个字节
int sendBytes = 0;
int ret;
naluType = frame[0];
if (frameSize <= RTP_MAX_PKT_SIZE) // nalu长度小于最大包场：单一NALU单元模式
{
/*
* 0 1 2 3 4 5 6 7 8 9
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |F|NRI| Type | a single NAL unit ... |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
memcpy(rtpPacket->payload, frame, frameSize);
ret = rtpSendPacket(socket, ip, port, rtpPacket, frameSize);
if(ret < 0)
return -1;
rtpPacket->rtpHeader.seq++;
sendBytes += ret;
if ((naluType & 0x1F) == 7 || (naluType & 0x1F) == 8) // 如果是SPS、PPS就不需要加时间戳
goto out;
}
else // nalu长度小于最大包场：分片模式
{
/*
* 0 1 2
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | FU indicator | FU header | FU payload ... |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
/*
* FU Indicator
* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |F|NRI| Type |
* +---------------+
*/
/*
* FU Header
* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |S|E|R| Type |
* +---------------+
*/
int pktNum = frameSize / RTP_MAX_PKT_SIZE; // 有几个完整的包
int remainPktSize = frameSize % RTP_MAX_PKT_SIZE; // 剩余不完整包的大小
int i, pos = 1;
/* 发送完整的包 */
for (i = 0; i < pktNum; i++)
{
rtpPacket->payload[0] = (naluType & 0x60) | 28;
rtpPacket->payload[1] = naluType & 0x1F;
if (i == 0) //第一包数据
rtpPacket->payload[1] |= 0x80; // start
else if (remainPktSize == 0 && i == pktNum - 1) //最后一包数据
rtpPacket->payload[1] |= 0x40; // end
memcpy(rtpPacket->payload+2, frame+pos, RTP_MAX_PKT_SIZE);
ret = rtpSendPacket(socket, ip, port, rtpPacket, RTP_MAX_PKT_SIZE+2);
if(ret < 0)
return -1;
rtpPacket->rtpHeader.seq++;
sendBytes += ret;
pos += RTP_MAX_PKT_SIZE;
}
/* 发送剩余的数据 */
if (remainPktSize > 0)
{
rtpPacket->payload[0] = (naluType & 0x60) | 28;
rtpPacket->payload[1] = naluType & 0x1F;
rtpPacket->payload[1] |= 0x40; //end
memcpy(rtpPacket->payload+2, frame+pos, remainPktSize+2);
ret = rtpSendPacket(socket, ip, port, rtpPacket, remainPktSize+2);
if(ret < 0)
return -1;
rtpPacket->rtpHeader.seq++;
sendBytes += ret;
}
}
out:
return sendBytes;
}
int main(int argc, char* argv[])
{
int socket;
int fd;
int fps = 25;
int startCode;
struct RtpPacket* rtpPacket;
uint8_t* frame;
uint32_t frameSize;
fd = open(H264_FILE_NAME, O_RDONLY);
if(fd < 0)
{
printf("failed to open %s\n", H264_FILE_NAME);
return -1;
}
socket = createUdpSocket();
if(socket < 0)
{
printf("failed to create socket\n");
return -1;
}
rtpPacket = (struct RtpPacket*)malloc(500000);
frame = (uint8_t*)malloc(500000);
rtpHeaderInit(rtpPacket, 0, 0, 0, RTP_VESION, RTP_PAYLOAD_TYPE_H264, 0,
0, 0, 0x88923423);
while(1)
{
frameSize = getFrameFromH264File(fd, frame, 500000);
if(frameSize < 0)
{
printf("read err\n");
continue;
}
if(startCode3(frame))
startCode = 3;
else
startCode = 4;
frameSize -= startCode;
rtpSendH264Frame(socket, MULTICAST_IP, MULTICAST_PORT,
rtpPacket, frame+startCode, frameSize);
rtpPacket->rtpHeader.timestamp += 90000/FPS;
usleep(1000*1000/fps);
}
free(rtpPacket);
free(frame);
return 0;
}
rtp.h
#ifndef _RTP_H_
#define _RTP_H_
#include <stdint.h>
#define RTP_VESION 2
#define RTP_PAYLOAD_TYPE_H264 96
#define RTP_PAYLOAD_TYPE_AAC 97
#define RTP_HEADER_SIZE 12
#define RTP_MAX_PKT_SIZE 1400
/*
*
* 0 1 2 3
* 7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |V=2|P|X| CC |M| PT | sequence number |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | timestamp |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | synchronization source (SSRC) identifier |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | contributing source (CSRC) identifiers |
* : .... :
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
*/
struct RtpHeader
{
/* byte 0 */
uint8_t csrcLen:4;
uint8_t extension:1;
uint8_t padding:1;
uint8_t version:2;
/* byte 1 */
uint8_t payloadType:7;
uint8_t marker:1;
/* bytes 2,3 */
uint16_t seq;
/* bytes 4-7 */
uint32_t timestamp;
/* bytes 8-11 */
uint32_t ssrc;
};
struct RtpPacket
{
struct RtpHeader rtpHeader;
uint8_t payload[0];
};
void rtpHeaderInit(struct RtpPacket* rtpPacket, uint8_t csrcLen, uint8_t extension,
uint8_t padding, uint8_t version, uint8_t payloadType, uint8_t marker,
uint16_t seq, uint32_t timestamp, uint32_t ssrc);
int rtpSendPacket(int socket, const char* ip, int16_t port, struct RtpPacket* rtpPacket, uint32_t dataSize);
#endif //_RTP_H_
rtp.c
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "rtp.h"
void rtpHeaderInit(struct RtpPacket* rtpPacket, uint8_t csrcLen, uint8_t extension,
uint8_t padding, uint8_t version, uint8_t payloadType, uint8_t marker,
uint16_t seq, uint32_t timestamp, uint32_t ssrc)
{
rtpPacket->rtpHeader.csrcLen = csrcLen;
rtpPacket->rtpHeader.extension = extension;
rtpPacket->rtpHeader.padding = padding;
rtpPacket->rtpHeader.version = version;
rtpPacket->rtpHeader.payloadType = payloadType;
rtpPacket->rtpHeader.marker = marker;
rtpPacket->rtpHeader.seq = seq;
rtpPacket->rtpHeader.timestamp = timestamp;
rtpPacket->rtpHeader.ssrc = ssrc;
}
int rtpSendPacket(int socket, const char* ip, int16_t port, struct RtpPacket* rtpPacket, uint32_t dataSize)
{
struct sockaddr_in addr;
int ret;
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = inet_addr(ip);
rtpPacket->rtpHeader.seq = htons(rtpPacket->rtpHeader.seq);
rtpPacket->rtpHeader.timestamp = htonl(rtpPacket->rtpHeader.timestamp);
rtpPacket->rtpHeader.ssrc = htonl(rtpPacket->rtpHeader.ssrc);
ret = sendto(socket, (void*)rtpPacket, dataSize+RTP_HEADER_SIZE, 0,
(struct sockaddr*)&addr, sizeof(addr));
rtpPacket->rtpHeader.seq = ntohs(rtpPacket->rtpHeader.seq);
rtpPacket->rtpHeader.timestamp = ntohl(rtpPacket->rtpHeader.timestamp);
rtpPacket->rtpHeader.ssrc = ntohl(rtpPacket->rtpHeader.ssrc);
return ret;
}
四、测试
将multicast.c、rtp.h、rtp.c保存下来
编译运行，程序默认会打开test.h264的视频文件，如果你没有视频源的话，可以从RtspServer的example目录下获取
# gcc multicast.c rtp.c
# ./a.out
将sdp保存为multicast.sdp
a=type:broadcast
a=rtcp-unicast: reflection
m=video 9832 RTP/AVP 96
c=IN IP4 239.255.255.11/255
a=rtpmap:96 H264/90000
a=framerate:25
使用vlc打开sdp文件
# vlc multicast.sdp
-
运行效果
上一篇： python爬虫需要安装哪些库
下一篇： 2、RTSP协议的实现
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