Mpeg2/ts Get PMT PID

A simple function to get the PMT PID from the specified mpeg2/ts file,

Note the comments in the code.

#define MAKE_PID (P) (((p[0]<<8) + p[1]) & 0X1FFF)[HTML]  View Plain  copy ushort getpmtpid (const char* filename)    {   #define  TSPACKET_SIZE     188         ushort  pid;       uchar buf[TSPACKET_SIZE];        uchar* p = buf;       FILE*  fp;           fp = fopen (filename,  "RB");       if   (fp == null)  {           fprintf (stderr,   "failed to open the file %s: %s\n",  filename, strerror (errno));            return 0;        }          while  (fread (BUF,&NBSP;1,&NBSP;TSPACKET_SIZE,&NBSP;FP) & nbsp;== tspacket_size)  {           if  (Buf[0]  != mpeg_ts_sync_byte)  {                fprintf (stderr,  "no sync byte where one was expected!\n") ;               break;            }               p = buf;           pid = make_pid (( p+1));           if  ( pid != 0 )  {               //  not Pat pack                continue;           }              // skip  the TS header           p += mpeg_ ts_header_size; //@MPEG_TS_HEADER_SIZE  = 4               // Adaptation field exist or not            if  ((buf[3] >> 4 & 0x03)  &  0x2)  {               fprintf ( stderr,  "adaptation field exist\n");                p += 1 + p[0];  // p[0] is adaptation  Field length,  1 for length field            }               // p[0]  for  point field length,  1 for point field            p += 1 + p[0];               // 8  is the length of the PAT header, and if a table header is defined, use the sizeof operator             p += 8;               // nit program exist??            if ( * ((ushort*) p)  == 0)  {                p += 4; //  pat's program structure is 4 bytes            }               p += 2; //  program number is two bytes               fclose (FP);    &Nbsp;      return make_pid (p);       }           fclose (FP);       return 0;   }