接收rtp over tcp 负载数据代码

场景

    在建立RTSP连接之后，通过rtp over tcp接收视频数据，在下面的例子中获取到的数据流，还是存在相隔2个RTP负载的问题，但是从字节来看，RTP的负载非常小，应该对数据没有任何的影响

说明

    m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);第二个参数是真实读取到的字节数，第三个参数是指定当前读取多少个字节

代码

struct RTPHeader

{

unsigned char szHeader[4];

};

unsigned short sRTPPayLoadLen = 0;//整个RTP报文的长度，由$ 0x00|0x01 后面的两个字节决定

unsigned char cOneBytes = 0;//保存第一个字节，进行判断是否是$，从而判断是否是RTP负载包，还是RTSP指令包

char* pszOneBytes = (char*)&cOneBytes;//接收数据只能通过符号字符，因此采用强制转换

int nRealReadLen = 0;//保存了每一次读取的字节个数

int nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);//建立rtsp链接之后，开始读取第一个字节

if (nRet <= 0)

{

exit(0);

}

while (true)

{

if ('$' == cOneBytes)

{

nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);

if ((nRet <= 0) || (nRet != 1)) break;

if ('$' == cOneBytes) continue;//两个$$相连也是有可能的，重新循环

if (0x00 == cOneBytes || 0x01 == cOneBytes)//读取到有效的数据

{

nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);//尝试读取高位的负载长度

if ((nRet <= 0) || (nRet != 1)) break;

if ('$' == cOneBytes) continue;

sRTPPayLoadLen = cOneBytes << 8;

if (sRTPPayLoadLen < -1 || sRTPPayLoadLen > 1500) continue;//高位有可能是0，因为有时候多个RTP只是携带格式信息，但是没有携带数据负载

nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);//尝试读取低位的负载长度

if ((nRet <= 0) || (nRet != 1)) break;

//if ('$' == cOneBytes) continue;//有可能低位刚好就是24，所以这一点是不需要担心的

sRTPPayLoadLen = sRTPPayLoadLen + cOneBytes;

if (sRTPPayLoadLen < 0 || sRTPPayLoadLen > 1500) continue;//数据不可能超过1500,局域网传输带宽要求

char szRTPPayLoadContent[1500] = { 0 };

nRealReadLen = 0;

nRet = m_sock->RecvBuffer(szRTPPayLoadContent, nRealReadLen, sRTPPayLoadLen);

RTPHeader* pHeader = (RTPHeader*)szRTPPayLoadContent;

unsigned short sRTPSeq = (pHeader->szHeader[2] << 8) + pHeader->szHeader[3];

//std::cout << "curSeq:" << sRTPSeq << std::endl;

static int nLastSeq = sRTPSeq;

int nGap = sRTPSeq - nLastSeq;

if (nGap != 1)

{

std::cout << "rtp seq gap:" << nGap <<",lastSeq:"<<nLastSeq<<",curSeq:"<<sRTPSeq << std::endl;

}

nLastSeq = sRTPSeq;

//循环读取负载的长度报文，一次可能读取不了完整的一个RTP负载的报文

while (nRealReadLen < sRTPPayLoadLen)

{

memset(szRTPPayLoadContent, 0x00, 1500);

sRTPPayLoadLen = sRTPPayLoadLen - nRealReadLen;

nRealReadLen = 0;

nRet = m_sock->RecvBuffer(szRTPPayLoadContent, nRealReadLen, sRTPPayLoadLen);

}

}

}

nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);

if ((nRet <= 0) || (nRet != 1)) break;

}