Mpeg2 TS stream parser for media source.

media/mp2t/ts_section_pmt.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/mp2t/ts_section_pmt.h"
+
+#include <map>
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/mp2t/mp2t_common.h"
+
+namespace media {
+namespace mp2t {
+
+TsSectionPmt::TsSectionPmt(const RegisterPesCb& register_pes_cb)
+    : register_pes_cb_(register_pes_cb) {
+}
+
+TsSectionPmt::~TsSectionPmt() {
+}
+
+bool TsSectionPmt::ParsePsiSection(BitReader* bit_reader) {
+  // Read up to |last_section_number|.
+  int table_id;
+  bool section_syntax_indicator;
+  bool dummy_zero;
+  int reserved;
+  int section_length;
+  int program_number;
+  int version_number;
+  bool current_next_indicator;
+  int section_number;
+  int last_section_number;
+  RCHECK(bit_reader->ReadBits(8, &table_id));
+  RCHECK(bit_reader->ReadBits(1, &section_syntax_indicator));
+  RCHECK(bit_reader->ReadBits(1, &dummy_zero));
+  RCHECK(bit_reader->ReadBits(2, &reserved));
+  RCHECK(bit_reader->ReadBits(12, &section_length));
+  int section_start_marker = bit_reader->bits_available() / 8;
+
+  RCHECK(bit_reader->ReadBits(16, &program_number));
+  RCHECK(bit_reader->ReadBits(2, &reserved));
+  RCHECK(bit_reader->ReadBits(5, &version_number));
+  RCHECK(bit_reader->ReadBits(1, &current_next_indicator));
+  RCHECK(bit_reader->ReadBits(8, &section_number));
+  RCHECK(bit_reader->ReadBits(8, &last_section_number));
+
+  // Perform a few verifications:
+  // - table ID should be 2 for a PMT.
+  // - section_syntax_indicator should be one.
+  // - section length should not exceed 1021.
+  RCHECK(table_id == 0x2);
+  RCHECK(section_syntax_indicator);
+  RCHECK(!dummy_zero);
+  RCHECK(section_length <= 1021);
+  RCHECK(section_number == 0);
+  RCHECK(last_section_number == 0);
+
+  // TODO(damienv):
+  // Verify that there is no mismatch between the program number
+  // and the program number that was provided in a PAT for the current PMT.
+
+  // Read the end of the fixed length section.
+  int pcr_pid;
+  int program_info_length;
+  RCHECK(bit_reader->ReadBits(3, &reserved));
+  RCHECK(bit_reader->ReadBits(13, &pcr_pid));
+  RCHECK(bit_reader->ReadBits(4, &reserved));
+  RCHECK(bit_reader->ReadBits(12, &program_info_length));
+  RCHECK(program_info_length < 1024);
+
+  // Read the program info descriptor.
+  // TODO(damienv): check wether any of the descriptors could be useful.
+  // Defined in section 2.6 of ISO-13818.
+  RCHECK(bit_reader->SkipBits(8 * program_info_length));
+
+  // Read the ES description table.
+  // 5 bytes: minimum size of an ES descriptor.
+  int section_remaining_size = section_length -
+      (section_start_marker - bit_reader->bits_available() / 8);
+  std::map<int, int> pid_map;
+  while (section_remaining_size >= 5) {

[acolwell GONE FROM CHROMIUM, 2013/09/18 01:46:05]

nit: Can't you reorganize the math so this condition can become
(bit_reader->bits_available() > pid_map_end_marker) and you don't have to update
section_remaining_size inside the loop?

[damienv1, 2013/09/18 21:40:17]

Done.

+    int stream_type;
+    int reserved;
+    int pid_es;
+    int es_info_length;
+    RCHECK(bit_reader->ReadBits(8, &stream_type));
+    RCHECK(bit_reader->ReadBits(3, &reserved));
+    RCHECK(bit_reader->ReadBits(13, &pid_es));
+    RCHECK(bit_reader->ReadBits(4, &reserved));
+    RCHECK(bit_reader->ReadBits(12, &es_info_length));
+    section_remaining_size -= 5;
+
+    // Do not register the PID right away.
+    // Wait for the end of the section to be fully parsed
+    // to make sure there is no error.
+    pid_map.insert(std::pair<int, int>(pid_es, stream_type));
+
+    // Read the ES info descriptors.
+    // TODO(damienv): check wether any of the descriptors could be useful.
+    // Defined in section 2.6 of ISO-13818.
+    RCHECK(section_length >= es_info_length);
+    RCHECK(bit_reader->SkipBits(8 * es_info_length));
+    section_remaining_size -= es_info_length;
+  }
+
+  // Read the CRC.
+  int crc32;
+  RCHECK(section_remaining_size == 4);
+  RCHECK(bit_reader->ReadBits(32, &crc32));
+
+  // Once the PMT has been proved to be correct, register the PIDs.
+  for (std::map<int, int>::iterator it = pid_map.begin();
+       it != pid_map.end(); ++it)
+    register_pes_cb_.Run(it->first, it->second);
+
+  return true;
+}
+
+void TsSectionPmt::ResetPsiSection() {
+}
+
+}  // namespace mp2t
+}  // namespace media
+