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// Copyright 2014 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/formats/mp2t/ts_packet.h"
#include "base/memory/scoped_ptr.h"
#include "media/base/bit_reader.h"
#include "media/formats/mp2t/mp2t_common.h"
namespace media {
namespace mp2t {
static const uint8 kTsHeaderSyncword = 0x47;
// static
int TsPacket::Sync(const uint8* buf, int size) {
int k = 0;
for (; k < size; k++) {
// Verify that we have 4 syncwords in a row when possible,
// this should improve synchronization robustness.
// TODO(damienv): Consider the case where there is garbage
// between TS packets.
bool is_header = true;
for (int i = 0; i < 4; i++) {
int idx = k + i * kPacketSize;
if (idx >= size)
break;
if (buf[idx] != kTsHeaderSyncword) {
DVLOG(LOG_LEVEL_TS)
<< "ByteSync" << idx << ": "
<< std::hex << static_cast<int>(buf[idx]) << std::dec;
is_header = false;
break;
}
}
if (is_header)
break;
}
DVLOG_IF(1, k != 0) << "SYNC: nbytes_skipped=" << k;
return k;
}
// static
TsPacket* TsPacket::Parse(const uint8* buf, int size) {
if (size < kPacketSize) {
DVLOG(1) << "Buffer does not hold one full TS packet:"
<< " buffer_size=" << size;
return NULL;
}
DCHECK_EQ(buf[0], kTsHeaderSyncword);
if (buf[0] != kTsHeaderSyncword) {
DVLOG(1) << "Not on a TS syncword:"
<< " buf[0]="
<< std::hex << static_cast<int>(buf[0]) << std::dec;
return NULL;
}
scoped_ptr<TsPacket> ts_packet(new TsPacket());
bool status = ts_packet->ParseHeader(buf);
if (!status) {
DVLOG(1) << "Parsing header failed";
return NULL;
}
return ts_packet.release();
}
TsPacket::TsPacket() {
}
TsPacket::~TsPacket() {
}
bool TsPacket::ParseHeader(const uint8* buf) {
BitReader bit_reader(buf, kPacketSize);
payload_ = buf;
payload_size_ = kPacketSize;
// Read the TS header: 4 bytes.
int syncword;
int transport_error_indicator;
int payload_unit_start_indicator;
int transport_priority;
int transport_scrambling_control;
int adaptation_field_control;
RCHECK(bit_reader.ReadBits(8, &syncword));
RCHECK(bit_reader.ReadBits(1, &transport_error_indicator));
RCHECK(bit_reader.ReadBits(1, &payload_unit_start_indicator));
RCHECK(bit_reader.ReadBits(1, &transport_priority));
RCHECK(bit_reader.ReadBits(13, &pid_));
RCHECK(bit_reader.ReadBits(2, &transport_scrambling_control));
RCHECK(bit_reader.ReadBits(2, &adaptation_field_control));
RCHECK(bit_reader.ReadBits(4, &continuity_counter_));
payload_unit_start_indicator_ = (payload_unit_start_indicator != 0);
payload_ += 4;
payload_size_ -= 4;
// Default values when no adaptation field.
discontinuity_indicator_ = false;
random_access_indicator_ = false;
// Done since no adaptation field.
if ((adaptation_field_control & 0x2) == 0)
return true;
// Read the adaptation field if needed.
int adaptation_field_length;
RCHECK(bit_reader.ReadBits(8, &adaptation_field_length));
DVLOG(LOG_LEVEL_TS) << "adaptation_field_length=" << adaptation_field_length;
payload_ += 1;
payload_size_ -= 1;
if ((adaptation_field_control & 0x1) == 0 &&
adaptation_field_length != 183) {
DVLOG(1) << "adaptation_field_length=" << adaptation_field_length;
return false;
}
if ((adaptation_field_control & 0x1) == 1 &&
adaptation_field_length > 182) {
DVLOG(1) << "adaptation_field_length=" << adaptation_field_length;
// This is not allowed by the spec.
// However, some badly encoded streams are using
// adaptation_field_length = 183
return false;
}
// adaptation_field_length = '0' is used to insert a single stuffing byte
// in the adaptation field of a transport stream packet.
if (adaptation_field_length == 0)
return true;
bool status = ParseAdaptationField(&bit_reader, adaptation_field_length);
payload_ += adaptation_field_length;
payload_size_ -= adaptation_field_length;
return status;
}
bool TsPacket::ParseAdaptationField(BitReader* bit_reader,
int adaptation_field_length) {
DCHECK_GT(adaptation_field_length, 0);
int adaptation_field_start_marker = bit_reader->bits_available() / 8;
int discontinuity_indicator;
int random_access_indicator;
int elementary_stream_priority_indicator;
int pcr_flag;
int opcr_flag;
int splicing_point_flag;
int transport_private_data_flag;
int adaptation_field_extension_flag;
RCHECK(bit_reader->ReadBits(1, &discontinuity_indicator));
RCHECK(bit_reader->ReadBits(1, &random_access_indicator));
RCHECK(bit_reader->ReadBits(1, &elementary_stream_priority_indicator));
RCHECK(bit_reader->ReadBits(1, &pcr_flag));
RCHECK(bit_reader->ReadBits(1, &opcr_flag));
RCHECK(bit_reader->ReadBits(1, &splicing_point_flag));
RCHECK(bit_reader->ReadBits(1, &transport_private_data_flag));
RCHECK(bit_reader->ReadBits(1, &adaptation_field_extension_flag));
discontinuity_indicator_ = (discontinuity_indicator != 0);
random_access_indicator_ = (random_access_indicator != 0);
if (pcr_flag) {
int64 program_clock_reference_base;
int reserved;
int program_clock_reference_extension;
RCHECK(bit_reader->ReadBits(33, &program_clock_reference_base));
RCHECK(bit_reader->ReadBits(6, &reserved));
RCHECK(bit_reader->ReadBits(9, &program_clock_reference_extension));
}
if (opcr_flag) {
int64 original_program_clock_reference_base;
int reserved;
int original_program_clock_reference_extension;
RCHECK(bit_reader->ReadBits(33, &original_program_clock_reference_base));
RCHECK(bit_reader->ReadBits(6, &reserved));
RCHECK(
bit_reader->ReadBits(9, &original_program_clock_reference_extension));
}
if (splicing_point_flag) {
int splice_countdown;
RCHECK(bit_reader->ReadBits(8, &splice_countdown));
}
if (transport_private_data_flag) {
int transport_private_data_length;
RCHECK(bit_reader->ReadBits(8, &transport_private_data_length));
RCHECK(bit_reader->SkipBits(8 * transport_private_data_length));
}
if (adaptation_field_extension_flag) {
int adaptation_field_extension_length;
RCHECK(bit_reader->ReadBits(8, &adaptation_field_extension_length));
RCHECK(bit_reader->SkipBits(8 * adaptation_field_extension_length));
}
// The rest of the adaptation field should be stuffing bytes.
int adaptation_field_remaining_size = adaptation_field_length -
(adaptation_field_start_marker - bit_reader->bits_available() / 8);
RCHECK(adaptation_field_remaining_size >= 0);
for (int k = 0; k < adaptation_field_remaining_size; k++) {
int stuffing_byte;
RCHECK(bit_reader->ReadBits(8, &stuffing_byte));
// Unfortunately, a lot of streams exist in the field that do not fill
// the remaining of the adaptation field with the expected stuffing value:
// do not fail if that's the case.
DVLOG_IF(1, stuffing_byte != 0xff)
<< "Stream not compliant: invalid stuffing byte "
<< std::hex << stuffing_byte;
}
DVLOG(LOG_LEVEL_TS) << "random_access_indicator=" << random_access_indicator_;
return true;
}
} // namespace mp2t
} // namespace media
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