MPEG2/TS 获取Video PID

 从PMT表中获取Video PID的函数代码

 

GetPmtPid函数的实现见：http://blog.csdn.net/myaccella/article/details/6982596

#define MAKE_PID(p) (((p[0]<<8) + p[1]) & 0x1fff)
#define MAKE_WORD(h, l) (((h) << 8) | (l))

 

Little endian 的结构定义

typedef struct {
  unsigned stream_type  :8;

  unsigned elementary_PID_high :5;
  unsigned    :3;

  unsigned elementary_PID_low :8;

  unsigned ES_info_length_high :4;
  unsigned    :4;

  unsigned ES_info_length_low :8;
}MpegPmtStream_t;

 

typedef struct {
  unsigned table_id   :8;

  unsigned section_length_high  :4;
  unsigned     :2;
  unsigned    :1;
  unsigned section_syntax_indicator :1;
 
  unsigned section_length_low  :8;
 
  unsigned program_number_high  :8;

  unsigned program_number_low  :8;

  unsigned current_next_indicator :1;
  unsigned version_number  :5;
  unsigned     :2;

  unsigned section_number  :8;

  unsigned last_section_number  :8;
 
  unsigned PCR_PID_high   :5;
  unsigned    :3;

  unsigned PCR_PID_low   :8;
 
  unsigned program_info_length_high :4;
  unsigned    :4;
 
  unsigned program_info_length_low :8;
}MpegPmtHeader_t;

 

ushort GetVideoPid(const char* filename){#define TSPACKET_SIZE     188 #define CRC_SIZE          4ushort pid, pmtpid, videopid = 0;uchar buf[TSPACKET_SIZE];uchar* p = buf;MpegPmtHeader_t* header;MpegPmtStream_t* stream;FILE*  fp;int pos = 0;ushort section_len;pmtpid = GetPmtPid(filename);if (pmtpid == 0) {fprintf(stderr, "Unable to get PMT PID!\n");return 0;}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, 1, TSPACKET_SIZE, fp) == TSPACKET_SIZE) {if (buf[0] != MPEG_TS_SYNC_BYTE) { // @MPEG_TS_SYNC_BYTE = 0x47fprintf(stderr, "No sync byte!\n");break;}p = buf;pid = MAKE_PID((p+1));if( pid != pmtpid ) {// Not a  PMT packetcontinue;}// payload_unit_start_indicator 必须为1if (!(buf[1] >> 6 & 0x01)) {fprintf(stderr, "No payload_unit_start_indicator!\n");continue;}// Skip the TS headerp += MPEG_TS_HEADER_SIZE; //@MPEG_TS_HEADER_SIZE = 4// Adaptation field exist or notif ((buf[3] >> 4 & 0x03) & 0x2) {fprintf(stderr, "Adaptation field exist\n");p += 1 + p[0];  // p[0]是Adaptation field长度, 1为长度域}// p[0] 为 Point field长度， 1为Point fieldp += 1 + p[0];// Now p 指向 PMT表头        header = (MpegPmtHeader_t*)p;pos +=  sizeof(MpegPmtHeader_t); pos += MAKE_WORD(header->program_info_length_high, header->program_info_length_low);;// Parse stream tablesection_len = MAKE_WORD(header->section_length_high, header->section_length_low);while (pos < (section_len + 2) - CRC_SIZE) {stream = (MpegPmtStream_t*)(p + pos);// @MPEG_TS_STREAM_TYPE_VIDEO_2 = 0x02if (stream->stream_type == MPEG_TS_STREAM_TYPE_VIDEO_2) {videopid = MAKE_WORD(stream->elementary_PID_high, stream->elementary_PID_low);break;}// @MPEG_PMT_STREAM_HEADER_SIZE = 5pos +=  MPEG_PMT_STREAM_HEADER_SIZE     + MAKE_WORD(stream->ES_info_length_high, stream->ES_info_length_low);}}fclose(fp);return videopid;}