TS格式解析

// Program Association Table

typedef struct PAT_Packet_tag

{

    unsigned table_id                        : 8; //固定为0x00 ，标志是该表是PAT

    unsigned section_syntax_indicator        : 1; //段语法标志位，固定为1

    unsigned zero                            : 1; //0

    unsigned reserved_1                      : 2; // 保留位

    unsigned section_length                  : 12;//表示这个字节后面有用的字节数，包括CRC32

    unsigned transport_stream_id             : 16;//该传输流的ID，区别于一个网络中其它多路复用的流

    unsigned reserved_2                      : 2; // 保留位

    unsigned version_number                  : 5; //范围0-31，表示PAT的版本号

    unsigned current_next_indicator          : 1; //发送的PAT是当前有效还是下一个PAT有效

    unsigned section_number                  : 8; //分段的号码。PAT可能分为多段传输，第一段为00，以后每个分段加1，最多可能有256个分段

    unsigned last_section_number             : 8; //最后一个分段的号码

    // for(i=0; i<N; i++)

    // {

    unsigned program_number                  : 16;

    unsigned reserved_3                      : 3;

    unsigned network_PID                     : 16;  // 或者program_map_PID

    unsigned CRC_32                          : 32;

    // }

} PAT_Packet;

// Parse PAT

int Parse_PAT(unsigned char *pTSBuf, PAT_Packet *packet)

{

    TS_header TSheader;

    if (Parse_TS_packet_header(pTSBuf, &TSheader) != 0)

        return -1;

    if (TSheader.payload_unit_start_indicator == 0x01) // 表示含有PSI或者PES头

    {

        if (TSheader.PID == 0x0)  // 表示PAT

        {

             int iBeginlen = 4;

             int adaptation_field_length = pTSBuf[4];

             switch(TSheader.adaption_field_control)

             {

             case 0x0:                                    // reserved for future use by ISO/IEC

                  return -1;

             case 0x1:                                    // 无调整字段，仅含有效负载      

                  iBeginlen += pTSBuf[iBeginlen] + 1;  // + pointer_field

                  break;

             case 0x2:                                     // 仅含调整字段，无有效负载

                  return -1;

             case 0x3: // 调整字段后含有效负载

                 if (adaptation_field_length > 0)

                 {

                      iBeginlen += 1;                   // adaptation_field_length占8位

                      iBeginlen += adaptation_field_length; // + adaptation_field_length

                 }

                 else

                 {

                      iBeginlen += 1;                       // adaptation_field_length占8位

                 }

                 iBeginlen += pTSBuf[iBeginlen] + 1;           // + pointer_field

                 break;

            default:

                 break;

            }

            unsigned char *pPAT = pTSBuf + iBeginlen;

            packet->table_id                    = pTSBuf[0];

            packet->section_syntax_indicator    = pTSBuf[1] >> 7;

            packet->zero                        = pTSBuf[1] >> 6 & 0x1;

            packet->reserved_1                  = pTSBuf[1] >> 4 & 0x3;

            packet->section_length              = (pTSBuf[1] & 0x0F) << 8 | pTSBuf[2];

            packet->transport_stream_id         = pTSBuf[3] << 8 | pTSBuf[4];

            packet->reserved_2                  = pTSBuf[5] >> 6;

            packet->version_number              = pTSBuf[5] >> 1 &  0x1F;

            packet->current_next_indicator      = (pTSBuf[5] << 7) >> 7;

            packet->section_number              = pTSBuf[6];

            packet->last_section_number         = pTSBuf[7];

            int len = 0;

            len = 3 + packet->section_length;

            packet->CRC_32                      = (pTSBuf[len-4] & 0x000000FF) << 24

                                                | (pTSBuf[len-3] & 0x000000FF) << 16

                                                | (pTSBuf[len-2] & 0x000000FF) << 8

                                                | (pTSBuf[len-1] & 0x000000FF);

            int n = 0;

            for ( n = 0; n < (packet->section_length - 12); n += 4 )

            {

                 packet->program_number = pTSBuf[8 + n ] << 8 | pTSBuf[9 + n ];

                 packet->reserved_3                = pTSBuf[10 + n ] >> 5;

                 if ( packet->program_number == 0x00)

                 {

                     packet->network_PID = (pTSBuf[10 + n ] & 0x1F) << 8 | pTSBuf[11 + n ];

                 }

                 else

                 {

                     // 有效的PMT的PID,然后通过这个PID值去查找PMT包

                     program_map_PID = (pTSBuf[10 + n] & 0x1F) << 8 | pTSBuf[11 + n];

                 }

            }

            return 0;

         }

    }

    return -1;

}