understand RTP baotou

commonly RTSP The flow is based on UDP Agreement based , Header of each package (12 Bytes ) We call it RTP baotou

understand H264 Of nalu head

RTP Package format 1 ：RTP baotou +nalu head ( A byte )+ data
Format two ：RTP baotou +fu Subcontracting head ( Two bytes )+ data

Format 1

When nalu Data less than or equal to RTP The maximum length of the package will be
nalu Header format ：

F：forbidden_zero_bit.1 position , If there is a syntax conflict , Then for 1. When the network recognizes that there is a bit error in this unit , You can set it to 1, So that the receiver can lose the unit .

NRI：nal_ref_idc.2 position , Used to indicate that NALU The importance level of . The bigger the value is. , At present NALU The more important . More specific than 0 What value is taken when , There is no specific provision .

Type：5 position , Pointed out that NALU The type of . The details are shown in the table ：

Format two

When nalu The data is greater than RTP The maximum length of the package will be
fu Subcontracting header format ：
First byte ：

Follow up nalu The head is the same , It's just Type=28 nothing more
The second byte ：

S: 1 bit When set to 1, The start bit indicates fragmentation NAL The beginning of the unit . When following FU The load is not piecewise NAL Start of unit load , The start bit is set to 0.

E: 1 bit When set to 1, The end bit indicates fragmentation NAL The end of the unit , namely , The last byte of the load is also divided NAL The last byte of the unit .
When following FU The load is not piecewise NAL The last piece of the unit , The end bit is set to 0.

If it's not the first package and the last package S and E Set to 0

R: 1 bit
Must be set to reserved bit 0, The receiver must ignore this bit .

Type: 5 bits
Here Type Namely NALU In the header Type, take 1-23 The value of , Express NAL Unit load type definition

Server source code

main function

RTSP_PROGRESS_1 function

EventLoop_1 function

ScheduleConnections Function call RtspServer

RtspServer function

This function is RTSP The process that the server processes all kinds of received data and returns data . If you call the change function ERR_CONNECTION_CLOSE and ERR_GENERIC These two kinds of mistakes , Some resources will be released , It is mainly about the handling of connection problems .

int RtspServer(RTSP_buffer *rtsp, int rtsp_num)
{
    
	fd_set rset,wset;       /* Reading and writing I/O Description set */
	struct timeval t;
	int size;
	static char buffer[RTSP_BUFFERSIZE+1]; /* +1 to control the final '\0'*/
	int n;
	int res;
	struct sockaddr ClientAddr;
#ifdef RTSP_DEBUG
// fprintf(stderr, "%s, %d\n", __FUNCTION__, __LINE__);
#endif
// memset((void *)&ClientAddr,0,sizeof(ClientAddr));
	if (rtsp == NULL)
	{
    
		return ERR_NOERROR;
	}
	/* Variable initialization */
	FD_ZERO(&rset);
	FD_ZERO(&wset);
	t.tv_sec=0;				/*select  The time interval */
	t.tv_usec=100000;
	FD_SET(rtsp->fd,&rset);
	/* call select Wait for the corresponding descriptor to change */
	if (select(g_s32Maxfd+1,&rset,0,0,&t)<0)
	{
    
		fprintf(stderr,"select error %s %d\n", __FILE__, __LINE__);
		send_reply(500, NULL, rtsp);
		return ERR_GENERIC; //errore interno al server
	}
	/* There is something to read rtsp package */
	if (FD_ISSET(rtsp->fd,&rset))
	{
    
		memset(buffer,0,sizeof(buffer));
		size=sizeof(buffer)-1;  /* The last bit is used to fill in the string end identifier */
		/* Read data into buffer */
#ifdef RTSP_DEBUG
// fprintf(stderr, "tcp_read, %d\n", __LINE__);
#endif
		n= tcp_read(rtsp->fd, buffer, size, &ClientAddr);
		if (n==0)
		{
    
			return ERR_CONNECTION_CLOSE;
		}
		if (n<0)
		{
    
			fprintf(stderr,"read() error %s %d\n", __FILE__, __LINE__);
			send_reply(500, NULL, rtsp);                // Server internal error message 
			return ERR_GENERIC;
		}
		// Check whether the read data overflows 
		if (rtsp->in_size+n>RTSP_BUFFERSIZE)
		{
    
			fprintf(stderr,"RTSP buffer overflow (input RTSP message is most likely invalid).\n");
			send_reply(500, NULL, rtsp);
			return ERR_GENERIC;// Data overflow error 
		}
#ifdef RTSP_DEBUG
		fprintf(stderr,"INPUT_BUFFER was:%s\n", buffer);
#endif
		/* Fill in the data */
		memcpy(&(rtsp->in_buffer[rtsp->in_size]),buffer,n);
		rtsp->in_size+=n;
		// Empty buffer
		memset(buffer, 0, n);
		// Add client address information 
		memcpy(	&rtsp->stClientAddr, &ClientAddr, sizeof(ClientAddr));
		/* Processing buffer data , Conduct rtsp Handle */
		if ((res=RTSP_handler(rtsp, rtsp_num))==ERR_GENERIC)
		{
    
			fprintf(stderr,"Invalid input message.\n");
			return ERR_NOERROR;
		}
	}
	/* Send data */
	if (rtsp->out_size>0)
	{
    
		// Send data out 
		n= tcp_write(rtsp->fd,rtsp->out_buffer,rtsp->out_size);
		if (n<0)
		{
    
			fprintf(stderr,"tcp_write error %s %i\n", __FILE__, __LINE__);
			send_reply(500, NULL, rtsp);
			return ERR_GENERIC; //errore interno al server
		}
#ifdef RTSP_DEBUG
		//fprintf(stderr,"OUTPUT_BUFFER length %d\n%s\n", rtsp->out_size, rtsp->out_buffer);
#endif
		// Empty the send buffer 
		memset(rtsp->out_buffer, 0, rtsp->out_size);
		rtsp->out_size = 0;
	}
	// if necessary RTCP Join right here RTCP Data reception , And stored in the cache .
	// And then in schedule_do Process it in the thread .
	//rtcp Control processing , Check read RTCP The datagram 
	return ERR_NOERROR;
}

RTSP_handler function

RTSP_state_machine function

Main call RTSP_state_machine(pRtspBuf, s32Meth); Function to process various client request messages , Then respond to the corresponding response message .

The appended drawings , Client and server RTSP Interaction protocol

schedule1_do function

The function is too long to post
This is in RTSP_PROGRESS_1 Medium ScheduleInit_1 Call in function
schedule_do The main function is to open h264 A file called RtpSend Function to package data RTP Send out .

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