本文介绍网络协议数据的处理程序。网络协议数据在视频播放器中的位置如下所示。
本文中的程序是一个UDP/RTP协议流媒体数据解析器。该程序可以分析UDP协议中的RTP 包头中的内容,以及RTP负载中MPEG-TS封装格式的信息。通过修改该程序可以实现不同的UDP/RTP协议数据处理功能。原理
MPEG-TS封装格式数据打包为RTP/UDP协议然后发送出去的流程如下图所示。图中首先每7个MPEG-TS Packet打包为一个RTP,然后每个RTP再打包为一个UDP。其中打包RTP的方法就是在MPEG-TS数据前面加上RTP Header,而打包RTP的方法就是在RTP数据前面加上UDP Header。
有关MPEG-TS、RTP、UDP的知识不再详细介绍,可以参考相关的文档了解其中的细节信息。本文记录的程序是一个收取流媒体的程序,因此本文程序的流程和上述发送MPEG-TS的流程正好是相反的。该程序可以通过Socket编程收取UDP包,解析其中的RTP包的信息,然后再解析RTP包中MPEG-TS Packet的信息。
#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")
#pragma pack(1)
/*
* [memo] FFmpeg stream Command:
* ffmpeg -re -i sintel.ts -f mpegts udp://127.0.0.1:8880
* ffmpeg -re -i sintel.ts -f rtp_mpegts udp://127.0.0.1:8880
*/
typedef struct RTP_FIXED_HEADER{
/* byte 0 */
unsigned char csrc_len:4; /* expect 0 */
unsigned char extension:1; /* expect 1 */
unsigned char padding:1; /* expect 0 */
unsigned char version:2; /* expect 2 */
/* byte 1 */
unsigned char payload:7;
unsigned char marker:1; /* expect 1 */
/* bytes 2, 3 */
unsigned short seq_no;
/* bytes 4-7 */
unsigned long timestamp;
/* bytes 8-11 */
unsigned long ssrc; /* stream number is used here. */
} RTP_FIXED_HEADER;
typedef struct MPEGTS_FIXED_HEADER {
unsigned sync_byte: 8;
unsigned transport_error_indicator: 1;
unsigned payload_unit_start_indicator: 1;
unsigned transport_priority: 1;
unsigned PID: 13;
unsigned scrambling_control: 2;
unsigned adaptation_field_exist: 2;
unsigned continuity_counter: 4;
} MPEGTS_FIXED_HEADER;
int simplest_udp_parser(int port)
{
WSADATA wsaData;
WORD sockVersion = MAKEWORD(2,2);
int cnt=0;
//FILE *myout=fopen("output_log.txt","wb+");
FILE *myout=stdout;
FILE *fp1=fopen("output_dump.ts","wb+");
if(WSAStartup(sockVersion, &wsaData) != 0){
return 0;
}
SOCKET serSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(serSocket == INVALID_SOCKET){
printf("socket error !");
return 0;
}
sockaddr_in serAddr;
serAddr.sin_family = AF_INET;
serAddr.sin_port = htons(port);
serAddr.sin_addr.S_un.S_addr = INADDR_ANY;
if(bind(serSocket, (sockaddr *)&serAddr, sizeof(serAddr)) == SOCKET_ERROR){
printf("bind error !");
closesocket(serSocket);
return 0;
}
sockaddr_in remoteAddr;
int nAddrLen = sizeof(remoteAddr);
//How to parse?
int parse_rtp=1;
int parse_mpegts=1;
printf("Listening on port %d\n",port);
char recvData[10000];
while (1){
int pktsize = recvfrom(serSocket, recvData, 10000, 0, (sockaddr *)&remoteAddr, &nAddrLen);
if (pktsize > 0){
//printf("Addr:%s\r\n",inet_ntoa(remoteAddr.sin_addr));
//printf("packet size:%d\r\n",pktsize);
//Parse RTP
//
if(parse_rtp!=0){
char payload_str[10]={0};
RTP_FIXED_HEADER rtp_header;
int rtp_header_size=sizeof(RTP_FIXED_HEADER);
//RTP Header
memcpy((void *)&rtp_header,recvData,rtp_header_size);
//RFC3551
char payload=rtp_header.payload;
switch(payload){
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
case 8:
case 9:
case 10:
case 11:
case 12:
case 13:
case 14:
case 15:
case 16:
case 17:
case 18: sprintf(payload_str,"Audio");break;
case 31: sprintf(payload_str,"H.261");break;
case 32: sprintf(payload_str,"MPV");break;
case 33: sprintf(payload_str,"MP2T");break;
case 34: sprintf(payload_str,"H.263");break;
case 96: sprintf(payload_str,"H.264");break;
default:sprintf(payload_str,"other");break;
}
unsigned int timestamp=ntohl(rtp_header.timestamp);
unsigned int seq_no=ntohs(rtp_header.seq_no);
fprintf(myout,"[RTP Pkt] %5d| %5s| %10u| %5d| %5d|\n",cnt,payload_str,timestamp,seq_no,pktsize);
//RTP Data
char *rtp_data=recvData+rtp_header_size;
int rtp_data_size=pktsize-rtp_header_size;
fwrite(rtp_data,rtp_data_size,1,fp1);
//Parse MPEGTS
if(parse_mpegts!=0&&payload==33){
MPEGTS_FIXED_HEADER mpegts_header;
for(int i=0;i<rtp_data_size;i=i+188){
if(rtp_data[i]!=0x47)
break;
//MPEGTS Header
//memcpy((void *)&mpegts_header,rtp_data+i,sizeof(MPEGTS_FIXED_HEADER));
fprintf(myout," [MPEGTS Pkt]\n");
}
}
}else{
fprintf(myout,"[UDP Pkt] %5d| %5d|\n",cnt,pktsize);
fwrite(recvData,pktsize,1,fp1);
}
cnt++;
}
}
closesocket(serSocket);
WSACleanup();
fclose(fp1);
return 0;
}
调用: simplest_udp_parser(8880);
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