接收rtp over tcp 負載數據代碼

場景

    在建立RTSP連接之后，通過rtp over tcp接收視頻數據，在下面的例子中獲取到的數據流，還是存在相隔2個RTP負載的問題，但是從字節來看，RTP的負載非常小，應該對數據沒有任何的影響

說明

    m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);第二個參數是真實讀取到的字節數，第三個參數是指定當前讀取多少個字節

代碼

struct RTPHeader

{

unsigned char szHeader[4];

};

unsigned short sRTPPayLoadLen = 0;//整個RTP報文的長度，由$ 0x00|0x01 后面的兩個字節決定

unsigned char cOneBytes = 0;//保存第一個字節，進行判斷是否是$，從而判斷是否是RTP負載包，還是RTSP指令包

char* pszOneBytes = (char*)&cOneBytes;//接收數據只能通過符號字符，因此采用強制轉換

int nRealReadLen = 0;//保存了每一次讀取的字節個數

int nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);//建立rtsp鏈接之后，開始讀取第一個字節

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;//兩個$$相連也是有可能的，重新循環

if (0x00 == cOneBytes || 0x01 == cOneBytes)//讀取到有效的數據

{

nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);//嘗試讀取高位的負載長度

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，因為有時候多個RTP只是攜帶格式信息，但是沒有攜帶數據負載

nRet = m_sock->RecvBuffer(pszOneBytes, nRealReadLen, 1);//嘗試讀取低位的負載長度

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

//if ('$' == cOneBytes) continue;//有可能低位剛好就是24，所以這一點是不需要擔心的

sRTPPayLoadLen = sRTPPayLoadLen + cOneBytes;

if (sRTPPayLoadLen < 0 || sRTPPayLoadLen > 1500) continue;//數據不可能超過1500,局域網傳輸帶寬要求

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;

//循環讀取負載的長度報文，一次可能讀取不了完整的一個RTP負載的報文

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;

}