// compiles successfully using a c++ version 2.7.2.1 compiler or later // typical environment SOLARIS 2.6 ( = SunOS 5.6 ) // To Compile: c++ MPEG2RTP.c -o MPEG2RTP // // Note: the function Send_RTP_Packet() is not implemented here. // However, the code here indicates where it should be called. // The Send_RTP_Packet() functions takes two arguments, the // name of the buffer (provided), and the number of bytes that // should be sent (also provided). So all is needed is to connect // to a socket and send the contents of the buffer. // // For more information about this code email: jhazboun@lucent.com // #include "MPEG2RTP.h" extern void display_rtp_hdr(); extern void display_mpeg_hdr(); extern void validate_file(); extern unsigned int read_picture_type(); extern unsigned int read_FBV(); extern unsigned int read_BFC(); extern unsigned int read_FFV(); extern unsigned int read_FFC(); extern unsigned int extract_temporal_reference(); extern unsigned int FIND_next_start_code(); extern void update_header(); unsigned char buf[MAX_RTP_PKT_LENGTH + 4]; //input buffer int indx = HEADER_LENGTH; //an index to the buffer enum reading_status state = SEQUENCE_HEADER; int max_to_send = MAX_RTP_PKT_LENGTH - 1; //index to where to send in buf unsigned int PACKET_DONE = 0; // when true, a packet is sent void main(int argc, char *argv[]) { int mpfd,j,i,v,bytes; unsigned int next_start_code; if (argc < 2) { printf("\nUSAGE: %s mpegfile\nExiting..\n\n",argv[0]); exit(0); } mpfd = open(argv[1], O_RDONLY); if (mpfd < 0 ) { printf("\nERROR: could not open input file %s\n\n",argv[1]); exit(0); } bzero((void *)&rtp_hdr,8); //zero-out the rtp fixed hdr bzero((void *)&mpeg_hdr,4); //zero-out the video specific hdr bzero((void *)buf,MAX_RTP_PKT_LENGTH + 4); //read the first packet from the mpeg file //always read 4 extra bytes in (in case there's a startcode there //but dont send more than MAX_RTP_PKT_LENGTH in one packet read(mpfd,&(buf[HEADER_LENGTH]),MAX_RTP_PKT_LENGTH-HEADER_LENGTH+4); validate_file(); do { /* initialization of the two RTP headers */ indx = HEADER_LENGTH; max_to_send = MAX_RTP_PKT_LENGTH; rtp_hdr.seq++; rtp_hdr.pt = MPA; rtp_hdr.version = 2; rtp_hdr.m =0; mpeg_hdr.S=0; mpeg_hdr.E=0; update_header(); PACKET_DONE = 0; while (!PACKET_DONE) /* start processing one packet */ { next_start_code = FIND_next_start_code(); switch(next_start_code) { case SEQUENCE_HEADER_CODE: mpeg_hdr.S=1; update_header(); state= SEQUENCE_HEADER; break; case PICTURE_START_CODE: mpeg_hdr.TR = extract_temporal_reference(); mpeg_hdr.P = read_picture_type(); //now read the motion vectors information if( (mpeg_hdr.P==2) || (mpeg_hdr.P==3)) { //if B- or P-type picture, need forward mv mpeg_hdr.FFV = read_FFV(); mpeg_hdr.FFC = read_FFC(); } if( mpeg_hdr.P==3) { // if B-type pictue, need backward mv mpeg_hdr.FBV = read_FBV(); mpeg_hdr.BFC = read_BFC(); } update_header(); state = PICTURE; break; case 0: break; } if ((next_start_code >0x100) && (next_start_code<0x1b0) ) { if (indx < 24) { // if it's a slice start code and follows GOP startcode, pic startcode, // or sequence header code mpeg_hdr.B = 1; update_header(); } state = SLICE; } if ((state == SLICE) && (PACKET_DONE) ) { //if the last byte of the payload is a slice end if (!((int)buf[indx+1]) && !((int)buf[indx+2]) && ((int)buf[indx+3]==1)) { mpeg_hdr.E = 1; update_header(); state = SLICE_END; } } if ( ((state==SLICE) || (state==SLICE_END)) && (next_start_code > 0x1af)) { rtp_hdr.m = 1; //set the M bit in the RTP fixed header update_header(); } } //end while: processing one packet //now send (max_to_send+1) bytes of the buffer "buf" //Send_RTP_Packet(buf,max_to_send+1); //Now copy the last bits in the buffer so they can be sent in the next pkt. v=12; for (j=0;j<(MAX_RTP_PKT_LENGTH-1-max_to_send+4+1);j++) buf[v++] = buf[j+max_to_send+1]; } while( (bytes=read(mpfd, (char *)&(buf[HEADER_LENGTH+ \ MAX_RTP_PKT_LENGTH-1-max_to_send+4]), \ (max_to_send - HEADER_LENGTH + 1))) \ >= (MAX_RTP_PKT_LENGTH - HEADER_LENGTH -4 )); //while !EOF if (bytes > 0) /* then process the last packet */ { update_header(); rtp_hdr.seq++; //now send the very last packet (# of bytes = (v-1+bytes) ) //Send_RTP_Packet(buf,(v-1)+bytes); } close(mpfd); } //================================================================== unsigned int FIND_next_start_code() //NOTE: all start codes ARE byte-aligned { unsigned int byte0=0,byte1=0,byte2=0,byte3=0,startcode=0; //while not startcode and have not exceeded max packet length while ( (indx < MAX_RTP_PKT_LENGTH) && (startcode == 0) ) { if (!((int)buf[indx+0] + (int)buf[indx+1]) && (((int)buf[indx+2])==1) ) { //printf("FOUND startcode %d\n",indx); byte0=(int)buf[indx+0]; byte1=(int)buf[indx+1]; byte2=(int)buf[indx+2]; byte3=(int)buf[indx+3]; startcode=(byte0 << 24) + (byte1 << 16) + (byte2 << 8) + byte3; indx=indx+4; } else {indx++;} } if ((startcode != 0) && (indx >= (MAX_RTP_PKT_LENGTH))) { //found startcode but it's at the end of payload, //therefore back up so the startcode will be sent in the next pkt indx=indx-5; max_to_send = indx; PACKET_DONE = 1; startcode =0; } else if ((startcode == 0) && (indx >= (MAX_RTP_PKT_LENGTH))) { //startcode not found, and reached the max payload size indx = indx - 1; PACKET_DONE = 1; max_to_send = indx; } return(startcode); } //======================================================== unsigned int extract_temporal_reference() // 10 bits { unsigned int low2bits=0,TR=0; // TR = temporal reference; TR = (unsigned int) (buf[indx]); TR << 2; low2bits = (unsigned int) (buf[indx+1]); TR |= (low2bits >> 6); return(TR); } //======================================================== unsigned int read_picture_type() { unsigned int pictype=0; pictype = (unsigned int) buf[indx+1]; pictype = (pictype >> 3) & (0x7); return (pictype); } //======================================================= unsigned int read_FFV() // 1 bit { return( (int) ((buf[indx+1] & (0x4)) >> 2)); } //======================================================= unsigned int read_FFC() // 3 bits { unsigned int FFC=0,lowbit=0; FFC = (int) (buf[indx+1] & (0x3)); FFC << 1; lowbit = (int) ((buf[indx+2]) & (0x80)); FFC = FFC | (lowbit >> 7 ); return(FFC); } //======================================================= unsigned int read_FBV() // 1 bit { return( (int) ((buf[indx+3] & (0x40))>>6) ); } //======================================================= unsigned int read_BFC() // 3 bits { return( (int) ( (buf[indx+3] & (0x56) ) >> 3 ) ); } //======================================================= void update_header() { strncpy((char *)&(buf[0]),(const char *)&rtp_hdr,8); strncpy((char *)&(buf[8]),(const char *)&mpeg_hdr,4); } //======================================================= void validate_file() { /* to validate the file, ensure the existance of a startcode */ int j=0,valid=0; while ((j++