rtcp多媒体控制协议调试

Posted 2021-02-06 dong1

1、rtcp是个非常小的多媒体控制协议，一般和jitter buffer一起用于rtp延时，抖动，丢包等处理。

1) rtcp应用描述，值得一看

详细的文档描述https://wenku.baidu.com/view/e21ee8e9b8f67c1cfad6b8f2.html

2) rtcp数据结构，消息构建，感谢网友。

https://www.cnblogs.com/Jimmly/archive/2009/08/03/1537468.html

https://www.cnblogs.com/Jimmly/archive/2009/09/02/1535648.html

 

c++的demo我改成c了，在code::blocks里调试的

rtcp.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

typedef struct _RTP_HEAD
{
    unsigned char    Version        : 2;
    unsigned char    Padding        : 1;
    unsigned char    Extension    : 1;
    unsigned char    Ccount        : 4;
    unsigned char    Marker        : 1;
    unsigned char    Ptype        : 7;
    unsigned char            Snumber;        //16bits
    unsigned int            Timestamp;        //32
    unsigned int            Ssrc;            //32
    unsigned int            Csrc;            //32
}RTP_HEAD,*pRTP_HEAD;

//RTCP的头部信息：
typedef struct _RTCP_HEAD
{
    unsigned char    Version        : 2;
    unsigned char    Padding        : 1;
    unsigned char    PCount        : 5;
    unsigned char    Ptype;            //8bits
    unsigned char            Length;            //16bits
}RTCP_HEAD,*pRTCP_HEAD;

 //RTP的bit图和代码实现：
 //     0                   1                   2                   3
 //     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //  0 |V=2|P|X|  CC   |M|     PT      |       sequence number         |
 //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //  4 |                           timestamp                           |
 //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //  8 |           synchronization source (SSRC) identifier            |
 //    +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 // 12 |                        payload header                         |
 //    |                             ....                              |
 //    +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 //    |                           payload                             |
 //    |                             ....                              |
 //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
void RTPCompose(  char *buffer,
                  int payloadType, int sequenceNum, int timestamp, int ssrc,
                  const char* payloadHeader, int payloadHeaderLength,
                  const char* payload, int payloadLength )
{
        //ASSERT( payload && payloadLength >= 0 );
        //buffer.resize( 12 + payloadHeaderLength + payloadLength );
        buffer = malloc(12 + payloadHeaderLength + payloadLength);
                     buffer[0]  = (char)(2<<6);                //  v=2, p=x=cc=0
                     buffer[1]  = (char)(payloadType & 0x127); // 7-bits for payload type
       *((unsigned short*)&buffer[2]) = (unsigned short)sequenceNum;
       *((unsigned int*)&buffer[4]) = (unsigned int)timestamp;
       *((unsigned int*)&buffer[8]) = (unsigned int)ssrc;
       memcpy( &buffer[12], payloadHeader, payloadHeaderLength );
       memcpy( &buffer[12+payloadHeaderLength], payload, payloadLength );
}

 //RTCP的bit图和代码实现：
 //        0                   1                   2                   3
 //        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //byte=0 |V=2|P|    RC   |   PT=SR=200   |             length            |
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //     4 |                         SSRC of sender                        |
 //       +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 //     8 |              NTP timestamp, most significant word             |
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //    12 |             NTP timestamp, least significant word             |
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //    16 |                         RTP timestamp                         |
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //    20 |                     sender‘s packet count                     |
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //    24 |                      sender‘s octet count                     |
 //       +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 //    28 |V=2|P|    SC   |  PT=SDES=202  |             length            |
 //       +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 //    32 |                          SSRC/CSRC_1                          |
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //    36 |    CNAME=1    |     length    | user and domain name        ...
 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
void RTCPSRCompose(  char *buffer,
                     int receptionCount, int ssrc, int64_t ntpTimestamp, int rtpTimestamp,
                     int sentPackets, int sentBytes,
                     const char* cname )
{
       //const string& cnameUTF8 = ConvertToUTF8( cname );
       //int length = 8 + 20 + 4 + 6 + cnameUTF8.size( ); // 注意此处可能存在bug。
                    //buffer.resize( length );
    buffer = malloc(8 + 20 + 4 + 6 + strlen(cname));
                    buffer[0]  = (char)(2<<6);                              //  V=2,  P=RC=0
                    buffer[1]  = (char)200;                                 // PT=SR=200
   *(unsigned short*)&buffer[2]  = 6;                                         // length (7 32-bit words, minus one)
   *(unsigned int*)&buffer[4]  = (unsigned int)ssrc;
   *(unsigned int*)&buffer[8]  = (unsigned int)(ntpTimestamp >> 32);        // High 32-bits
   *(unsigned int*)&buffer[12] = (unsigned int)(ntpTimestamp & 0xFFFFFFFF); // Low 32-bits
   *(unsigned int*)&buffer[16] = (unsigned int)rtpTimestamp;
   *(unsigned int*)&buffer[20] = (unsigned int)sentPackets;
   *(unsigned int*)&buffer[24] = (unsigned int)sentBytes;
                           buffer[28] = (char)(2<<6 & 1);                          //  V=2, P=0, SC=1
   *(unsigned short*)&buffer[30] = 0xFFFF;                                    // 注意这里应该填写长度，由于我们并没有数据因此无法填写。请程序员按自己的包长自己填写。
   *(unsigned int*)&buffer[32] = (unsigned int)ssrc;
                    buffer[36] = 1;                                         // CNAME=1
                    buffer[37] = strlen(cname);//(char)cnameUTF8.size( );
     memcpy( &buffer[38], cname, strlen(cname) );              // 同理此处请程序员自己填写
}

int main()
{
    printf("Hello world!
");
    return 0;
}