123 lines
3.8 KiB
C++
123 lines
3.8 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "media/formats/mp2t/ts_section_pat.h"
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#include <vector>
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#include "base/logging.h"
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#include "media/base/bit_reader.h"
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#include "media/formats/mp2t/mp2t_common.h"
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namespace media {
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namespace mp2t {
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TsSectionPat::TsSectionPat(const RegisterPmtCb& register_pmt_cb)
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: register_pmt_cb_(register_pmt_cb),
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version_number_(-1) {
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}
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TsSectionPat::~TsSectionPat() {
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}
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bool TsSectionPat::ParsePsiSection(BitReader* bit_reader) {
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// Read the fixed section length.
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int table_id;
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int section_syntax_indicator;
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int dummy_zero;
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int reserved;
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int section_length;
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int transport_stream_id;
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int version_number;
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int current_next_indicator;
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int section_number;
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int last_section_number;
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RCHECK(bit_reader->ReadBits(8, &table_id));
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RCHECK(bit_reader->ReadBits(1, §ion_syntax_indicator));
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RCHECK(bit_reader->ReadBits(1, &dummy_zero));
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RCHECK(bit_reader->ReadBits(2, &reserved));
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RCHECK(bit_reader->ReadBits(12, §ion_length));
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RCHECK(section_length >= 5);
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RCHECK(section_length <= 1021);
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RCHECK(bit_reader->ReadBits(16, &transport_stream_id));
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RCHECK(bit_reader->ReadBits(2, &reserved));
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RCHECK(bit_reader->ReadBits(5, &version_number));
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RCHECK(bit_reader->ReadBits(1, ¤t_next_indicator));
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RCHECK(bit_reader->ReadBits(8, §ion_number));
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RCHECK(bit_reader->ReadBits(8, &last_section_number));
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section_length -= 5;
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// Perform a few verifications:
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// - Table ID should be 0 for a PAT.
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// - section_syntax_indicator should be one.
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// - section length should not exceed 1021
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RCHECK(table_id == 0x0);
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RCHECK(section_syntax_indicator);
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RCHECK(!dummy_zero);
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// Both the program table and the CRC have a size multiple of 4.
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// Note for pmt_pid_count: minus 4 to account for the CRC.
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RCHECK((section_length % 4) == 0);
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int pmt_pid_count = (section_length - 4) / 4;
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// Read the variable length section: program table & crc.
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std::vector<int> program_number_array(pmt_pid_count);
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std::vector<int> pmt_pid_array(pmt_pid_count);
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for (int k = 0; k < pmt_pid_count; k++) {
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int reserved;
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RCHECK(bit_reader->ReadBits(16, &program_number_array[k]));
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RCHECK(bit_reader->ReadBits(3, &reserved));
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RCHECK(bit_reader->ReadBits(13, &pmt_pid_array[k]));
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}
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int crc32;
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RCHECK(bit_reader->ReadBits(32, &crc32));
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// Just ignore the PAT if not applicable yet.
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if (!current_next_indicator) {
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DVLOG(1) << "Not supported: received a PAT not applicable yet";
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return true;
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}
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// Ignore the program table if it hasn't changed.
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if (version_number == version_number_)
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return true;
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// Both the MSE and the HLS spec specifies that TS streams should convey
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// exactly one program.
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if (pmt_pid_count > 1) {
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DVLOG(1) << "Multiple programs detected in the Mpeg2 TS stream";
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return false;
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}
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// Can now register the PMT.
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#if !defined(NDEBUG)
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int expected_version_number = version_number;
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if (version_number_ >= 0)
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expected_version_number = (version_number_ + 1) % 32;
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DVLOG_IF(1, version_number != expected_version_number)
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<< "Unexpected version number: "
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<< version_number << " vs " << version_number_;
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#endif
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for (int k = 0; k < pmt_pid_count; k++) {
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if (program_number_array[k] != 0) {
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// Program numbers different from 0 correspond to PMT.
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register_pmt_cb_.Run(program_number_array[k], pmt_pid_array[k]);
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// Even if there are multiple programs, only one can be supported now.
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// HLS: "Transport Stream segments MUST contain a single MPEG-2 Program."
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break;
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}
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}
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version_number_ = version_number;
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return true;
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}
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void TsSectionPat::ResetPsiSection() {
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version_number_ = -1;
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}
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} // namespace mp2t
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} // namespace media
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