Mpeg2 TS stream parser for media source.

media/mpeg2/mpeg2ts_pat.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/mpeg2/mpeg2ts_pat.h"
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+
+namespace media {
+namespace mpeg2ts {
+
+Mpeg2TsPatParser::Mpeg2TsPatParser(RegisterPmtCb register_pmt_cb)
+    : register_pmt_cb_(register_pmt_cb),
+      version_number_(-1) {
+}
+
+Mpeg2TsPatParser::~Mpeg2TsPatParser() {
+}
+
+bool Mpeg2TsPatParser::ParsePsiSection(BitReader* bit_reader) {
+  int remaining_size = bit_reader->bits_available() / 8;
+
+  // Read the fixed section length.
+  if (remaining_size < 8) {
+    // This should not happen if the PAT size
+    // was correctly encoded into the stream.
+    LOG(WARNING) << "remaining_size=" << remaining_size;
+    return false;
+  }
+  int table_id;
+  DCHECK(bit_reader->ReadBits(8, &table_id));
+  if (table_id != 0x0) {
+    // Table ID should be 0 for a PAT.
+    LOG(WARNING) << "Unexpected table id: " << table_id;
+    return false;
+  }
+  bool section_syntax_indicator;
+  DCHECK(bit_reader->ReadBits(1, &section_syntax_indicator));
+  if (!section_syntax_indicator) {
+    LOG(WARNING) << "Unexpected section_syntax_indicator";
+    return false;
+  }
+  bool dummy_zero;
+  DCHECK(bit_reader->ReadBits(1, &dummy_zero));
+  if (dummy_zero) {
+    LOG(WARNING) << "Unexpected bit";
+    return false;
+  }
+  int reserved;
+  DCHECK(bit_reader->ReadBits(2, &reserved));
+  int section_length;
+  DCHECK(bit_reader->ReadBits(12, &section_length));
+  if (section_length >= 1021) {
+    return false;
+  }
+  int transport_stream_id;
+  DCHECK(bit_reader->ReadBits(16, &transport_stream_id));
+  DCHECK(bit_reader->ReadBits(2, &reserved));
+  int version_number;
+  DCHECK(bit_reader->ReadBits(5, &version_number));
+  bool current_next_indicator;
+  DCHECK(bit_reader->ReadBits(1, &current_next_indicator));
+  int section_number;
+  DCHECK(bit_reader->ReadBits(8, &section_number));
+  int last_section_number;
+  DCHECK(bit_reader->ReadBits(8, &last_section_number));
+  remaining_size -= 8;
+  section_length -= 5;
+
+  if (remaining_size < section_length) {
+    // This should not happen if the PAT size
+    // was correctly encoded into the stream.
+    LOG(WARNING) << "remaining_size=" << remaining_size;
+    return false;
+  }
+
+  // Minus 4 to account for the following CRC.
+  if ((section_length & 0x3) != 0) {
+    LOG(WARNING) << "PAT table size should be a multiple of 4";
+    return false;
+  }
+  int pmt_pid_count = (section_length - 4) / 4;
+  std::vector<int> program_number_array(pmt_pid_count);
+  std::vector<int> pmt_pid_array(pmt_pid_count);
+  for (int k = 0; k < pmt_pid_count; k++) {
+    if (remaining_size < 4) {
+      // This should not happen if the PAT size
+      // was correctly encoded into the stream.
+      LOG(WARNING) << "remaining_size=" << remaining_size;
+      return false;
+    }
+    DCHECK(bit_reader->ReadBits(16, &program_number_array[k]));
+    int reserved;
+    DCHECK(bit_reader->ReadBits(3, &reserved));
+    DCHECK(bit_reader->ReadBits(13, &pmt_pid_array[k]));
+    remaining_size -= 4;
+  }
+
+  // Read the CRC.
+  if (remaining_size < 4) {
+    // This should not happen if the PAT size
+    // was correctly encoded into the stream.
+    LOG(WARNING) << "remaining_size=" << remaining_size;
+    return false;
+  }
+  int crc32;
+  DCHECK(bit_reader->ReadBits(32, &crc32));
+  remaining_size -= 4;
+
+  // TODO(damienv): current_next_indicator flag is not handled at all.
+
+  // Register the PMT only once the PAT is known to be well formed
+  // and the version number has changed.
+  if (version_number_ != version_number) {
+    for (int k = 0; k < pmt_pid_count; k++) {
+      if (program_number_array[k] != 0) {
+        // Program numbers different from 0 correspond to PMT.
+        register_pmt_cb_.Run(program_number_array[k], pmt_pid_array[k]);
+        // Even if there are multiple programs, we can support only one.
+        break;
+      }
+    }
+    version_number_ = version_number;
+  }
+
+  // This should not happen if the PAT size
+  // was correctly encoded into the stream.
+  LOG_IF(WARNING, remaining_size != 0)
+      << "remaining_size=" << remaining_size;
+
+  return true;
+}
+
+}  // namespace mpeg2ts
+}  // namespace media