src/media/mp2t/ts_section_pmt.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/mp2t/ts_section_pmt.h"
   6
   7 #include <map>
   8
   9 #include "base/logging.h"
  10 #include "media/base/bit_reader.h"
  11 #include "media/mp2t/mp2t_common.h"
  12
  13 namespace media {
  14 namespace mp2t {
  15
  16 TsSectionPmt::TsSectionPmt(const RegisterPesCb& register_pes_cb)
  17     : register_pes_cb_(register_pes_cb) {
  18 }
  19
  20 TsSectionPmt::~TsSectionPmt() {
  21 }
  22
  23 bool TsSectionPmt::ParsePsiSection(BitReader* bit_reader) {
  24   // Read up to |last_section_number|.
  25   int table_id;
  26   int section_syntax_indicator;
  27   int dummy_zero;
  28   int reserved;
  29   int section_length;
  30   int program_number;
  31   int version_number;
  32   int current_next_indicator;
  33   int section_number;
  34   int last_section_number;
  35   RCHECK(bit_reader->ReadBits(8, &table_id));
  36   RCHECK(bit_reader->ReadBits(1, &section_syntax_indicator));
  37   RCHECK(bit_reader->ReadBits(1, &dummy_zero));
  38   RCHECK(bit_reader->ReadBits(2, &reserved));
  39   RCHECK(bit_reader->ReadBits(12, &section_length));
  40   int section_start_marker = bit_reader->bits_available() / 8;
  41
  42   RCHECK(bit_reader->ReadBits(16, &program_number));
  43   RCHECK(bit_reader->ReadBits(2, &reserved));
  44   RCHECK(bit_reader->ReadBits(5, &version_number));
  45   RCHECK(bit_reader->ReadBits(1, &current_next_indicator));
  46   RCHECK(bit_reader->ReadBits(8, &section_number));
  47   RCHECK(bit_reader->ReadBits(8, &last_section_number));
  48
  49   // Perform a few verifications:
  50   // - table ID should be 2 for a PMT.
  51   // - section_syntax_indicator should be one.
  52   // - section length should not exceed 1021.
  53   RCHECK(table_id == 0x2);
  54   RCHECK(section_syntax_indicator);
  55   RCHECK(!dummy_zero);
  56   RCHECK(section_length <= 1021);
  57   RCHECK(section_number == 0);
  58   RCHECK(last_section_number == 0);
  59
  60   // TODO(damienv):
  61   // Verify that there is no mismatch between the program number
  62   // and the program number that was provided in a PAT for the current PMT.
  63
  64   // Read the end of the fixed length section.
  65   int pcr_pid;
  66   int program_info_length;
  67   RCHECK(bit_reader->ReadBits(3, &reserved));
  68   RCHECK(bit_reader->ReadBits(13, &pcr_pid));
  69   RCHECK(bit_reader->ReadBits(4, &reserved));
  70   RCHECK(bit_reader->ReadBits(12, &program_info_length));
  71   RCHECK(program_info_length < 1024);
  72
  73   // Read the program info descriptor.
  74   // TODO(damienv): check wether any of the descriptors could be useful.
  75   // Defined in section 2.6 of ISO-13818.
  76   RCHECK(bit_reader->SkipBits(8 * program_info_length));
  77
  78   // Read the ES description table.
  79   // The end of the PID map if 4 bytes away from the end of the section
  80   // (4 bytes = size of the CRC).
  81   int pid_map_end_marker = section_start_marker - section_length + 4;
  82   std::map<int, int> pid_map;
  83   while (bit_reader->bits_available() > 8 * pid_map_end_marker) {
  84     int stream_type;
  85     int reserved;
  86     int pid_es;
  87     int es_info_length;
  88     RCHECK(bit_reader->ReadBits(8, &stream_type));
  89     RCHECK(bit_reader->ReadBits(3, &reserved));
  90     RCHECK(bit_reader->ReadBits(13, &pid_es));
  91     RCHECK(bit_reader->ReadBits(4, &reserved));
  92     RCHECK(bit_reader->ReadBits(12, &es_info_length));
  93
  94     // Do not register the PID right away.
  95     // Wait for the end of the section to be fully parsed
  96     // to make sure there is no error.
  97     pid_map.insert(std::pair<int, int>(pid_es, stream_type));
  98
  99     // Read the ES info descriptors.
 100     // TODO(damienv): check wether any of the descriptors could be useful.
 101     // Defined in section 2.6 of ISO-13818.
 102     RCHECK(bit_reader->SkipBits(8 * es_info_length));
 103   }
 104
 105   // Read the CRC.
 106   int crc32;
 107   RCHECK(bit_reader->ReadBits(32, &crc32));
 108
 109   // Once the PMT has been proved to be correct, register the PIDs.
 110   for (std::map<int, int>::iterator it = pid_map.begin();
 111        it != pid_map.end(); ++it)
 112     register_pes_cb_.Run(it->first, it->second);
 113
 114   return true;
 115 }
 116
 117 void TsSectionPmt::ResetPsiSection() {
 118 }
 119
 120 }  // namespace mp2t
 121 }  // namespace media
 122