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ts_section_pes.cc
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ts_section_pes.cc
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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 "packager/media/formats/mp2t/ts_section_pes.h"
#include "packager/base/logging.h"
#include "packager/base/strings/string_number_conversions.h"
#include "packager/media/base/bit_reader.h"
#include "packager/media/base/timestamp.h"
#include "packager/media/formats/mp2t/es_parser.h"
#include "packager/media/formats/mp2t/mp2t_common.h"
static const int kPesStartCode = 0x000001;
// Given that |time| is coded using 33 bits,
// UnrollTimestamp returns the corresponding unrolled timestamp.
// The unrolled timestamp is defined by:
// |time| + k * (2 ^ 33)
// where k is estimated so that the unrolled timestamp
// is as close as possible to |previous_unrolled_time|.
static int64_t UnrollTimestamp(int64_t previous_unrolled_time, int64_t time) {
// Mpeg2 TS timestamps have an accuracy of 33 bits.
const int nbits = 33;
// |timestamp| has a precision of |nbits|
// so make sure the highest bits are set to 0.
DCHECK_EQ((time >> nbits), 0);
// Consider 3 possibilities to estimate the missing high bits of |time|.
int64_t previous_unrolled_time_high = (previous_unrolled_time >> nbits);
int64_t time0 = ((previous_unrolled_time_high - 1) << nbits) | time;
int64_t time1 = ((previous_unrolled_time_high + 0) << nbits) | time;
int64_t time2 = ((previous_unrolled_time_high + 1) << nbits) | time;
// Select the min absolute difference with the current time
// so as to ensure time continuity.
int64_t diff0 = time0 - previous_unrolled_time;
int64_t diff1 = time1 - previous_unrolled_time;
int64_t diff2 = time2 - previous_unrolled_time;
if (diff0 < 0)
diff0 = -diff0;
if (diff1 < 0)
diff1 = -diff1;
if (diff2 < 0)
diff2 = -diff2;
int64_t unrolled_time;
int64_t min_diff;
if (diff1 < diff0) {
unrolled_time = time1;
min_diff = diff1;
} else {
unrolled_time = time0;
min_diff = diff0;
}
if (diff2 < min_diff)
unrolled_time = time2;
return unrolled_time;
}
static bool IsTimestampSectionValid(int64_t timestamp_section) {
// |pts_section| has 40 bits:
// - starting with either '0010' or '0011' or '0001'
// - and ending with a marker bit.
// See ITU H.222 standard - PES section.
// Verify that all the marker bits are set to one.
return ((timestamp_section & 0x1) != 0) &&
((timestamp_section & 0x10000) != 0) &&
((timestamp_section & 0x100000000LL) != 0);
}
static int64_t ConvertTimestampSectionToTimestamp(int64_t timestamp_section) {
return (((timestamp_section >> 33) & 0x7) << 30) |
(((timestamp_section >> 17) & 0x7fff) << 15) |
(((timestamp_section >> 1) & 0x7fff) << 0);
}
namespace shaka {
namespace media {
namespace mp2t {
TsSectionPes::TsSectionPes(scoped_ptr<EsParser> es_parser)
: es_parser_(es_parser.release()),
wait_for_pusi_(true),
previous_pts_valid_(false),
previous_pts_(0),
previous_dts_valid_(false),
previous_dts_(0) {
DCHECK(es_parser_);
}
TsSectionPes::~TsSectionPes() {
}
bool TsSectionPes::Parse(bool payload_unit_start_indicator,
const uint8_t* buf,
int size) {
// Ignore partial PES.
if (wait_for_pusi_ && !payload_unit_start_indicator)
return true;
bool parse_result = true;
if (payload_unit_start_indicator) {
// Try emitting a packet since we might have a pending PES packet
// with an undefined size.
// In this case, a unit is emitted when the next unit is coming.
int raw_pes_size;
const uint8_t* raw_pes;
pes_byte_queue_.Peek(&raw_pes, &raw_pes_size);
if (raw_pes_size > 0)
parse_result = Emit(true);
// Reset the state.
ResetPesState();
// Update the state.
wait_for_pusi_ = false;
}
// Add the data to the parser state.
if (size > 0)
pes_byte_queue_.Push(buf, size);
// Try emitting the current PES packet.
return (parse_result && Emit(false));
}
void TsSectionPes::Flush() {
// Try emitting a packet since we might have a pending PES packet
// with an undefined size.
Emit(true);
// Flush the underlying ES parser.
es_parser_->Flush();
}
void TsSectionPes::Reset() {
ResetPesState();
previous_pts_valid_ = false;
previous_pts_ = 0;
previous_dts_valid_ = false;
previous_dts_ = 0;
es_parser_->Reset();
}
bool TsSectionPes::Emit(bool emit_for_unknown_size) {
int raw_pes_size;
const uint8_t* raw_pes;
pes_byte_queue_.Peek(&raw_pes, &raw_pes_size);
// A PES should be at least 6 bytes.
// Wait for more data to come if not enough bytes.
if (raw_pes_size < 6)
return true;
// Check whether we have enough data to start parsing.
int pes_packet_length =
(static_cast<int>(raw_pes[4]) << 8) |
(static_cast<int>(raw_pes[5]));
if ((pes_packet_length == 0 && !emit_for_unknown_size) ||
(pes_packet_length != 0 && raw_pes_size < pes_packet_length + 6)) {
// Wait for more data to come either because:
// - there are not enough bytes,
// - or the PES size is unknown and the "force emit" flag is not set.
// (PES size might be unknown for video PES packet).
return true;
}
DVLOG(LOG_LEVEL_PES) << "pes_packet_length=" << pes_packet_length;
// Parse the packet.
bool parse_result = ParseInternal(raw_pes, raw_pes_size);
// Reset the state.
ResetPesState();
return parse_result;
}
bool TsSectionPes::ParseInternal(const uint8_t* raw_pes, int raw_pes_size) {
BitReader bit_reader(raw_pes, raw_pes_size);
// Read up to the pes_packet_length (6 bytes).
int packet_start_code_prefix;
int stream_id;
int pes_packet_length;
RCHECK(bit_reader.ReadBits(24, &packet_start_code_prefix));
RCHECK(bit_reader.ReadBits(8, &stream_id));
RCHECK(bit_reader.ReadBits(16, &pes_packet_length));
RCHECK(packet_start_code_prefix == kPesStartCode);
DVLOG(LOG_LEVEL_PES) << "stream_id=" << std::hex << stream_id << std::dec;
if (pes_packet_length == 0)
pes_packet_length = bit_reader.bits_available() / 8;
// Ignore the PES for unknown stream IDs.
// See ITU H.222 Table 2-22 "Stream_id assignments"
bool is_audio_stream_id = ((stream_id & 0xe0) == 0xc0);
bool is_video_stream_id = ((stream_id & 0xf0) == 0xe0);
if (!is_audio_stream_id && !is_video_stream_id)
return true;
// Read up to "pes_header_data_length".
int dummy_2;
int PES_scrambling_control;
int PES_priority;
int data_alignment_indicator;
int copyright;
int original_or_copy;
int pts_dts_flags;
int escr_flag;
int es_rate_flag;
int dsm_trick_mode_flag;
int additional_copy_info_flag;
int pes_crc_flag;
int pes_extension_flag;
int pes_header_data_length;
RCHECK(bit_reader.ReadBits(2, &dummy_2));
RCHECK(dummy_2 == 0x2);
RCHECK(bit_reader.ReadBits(2, &PES_scrambling_control));
RCHECK(bit_reader.ReadBits(1, &PES_priority));
RCHECK(bit_reader.ReadBits(1, &data_alignment_indicator));
RCHECK(bit_reader.ReadBits(1, ©right));
RCHECK(bit_reader.ReadBits(1, &original_or_copy));
RCHECK(bit_reader.ReadBits(2, &pts_dts_flags));
RCHECK(bit_reader.ReadBits(1, &escr_flag));
RCHECK(bit_reader.ReadBits(1, &es_rate_flag));
RCHECK(bit_reader.ReadBits(1, &dsm_trick_mode_flag));
RCHECK(bit_reader.ReadBits(1, &additional_copy_info_flag));
RCHECK(bit_reader.ReadBits(1, &pes_crc_flag));
RCHECK(bit_reader.ReadBits(1, &pes_extension_flag));
RCHECK(bit_reader.ReadBits(8, &pes_header_data_length));
int pes_header_start_size = bit_reader.bits_available() / 8;
// Compute the size and the offset of the ES payload.
// "6" for the 6 bytes read before and including |pes_packet_length|.
// "3" for the 3 bytes read before and including |pes_header_data_length|.
int es_size = pes_packet_length - 3 - pes_header_data_length;
int es_offset = 6 + 3 + pes_header_data_length;
RCHECK(es_size >= 0);
RCHECK(es_offset + es_size <= raw_pes_size);
// Read the timing information section.
bool is_pts_valid = false;
bool is_dts_valid = false;
int64_t pts_section = 0;
int64_t dts_section = 0;
if (pts_dts_flags == 0x2) {
RCHECK(bit_reader.ReadBits(40, &pts_section));
RCHECK((((pts_section >> 36) & 0xf) == 0x2) &&
IsTimestampSectionValid(pts_section));
is_pts_valid = true;
}
if (pts_dts_flags == 0x3) {
RCHECK(bit_reader.ReadBits(40, &pts_section));
RCHECK(bit_reader.ReadBits(40, &dts_section));
RCHECK((((pts_section >> 36) & 0xf) == 0x3) &&
IsTimestampSectionValid(pts_section));
RCHECK((((dts_section >> 36) & 0xf) == 0x1) &&
IsTimestampSectionValid(dts_section));
is_pts_valid = true;
is_dts_valid = true;
}
// Convert and unroll the timestamps.
int64_t media_pts(kNoTimestamp);
int64_t media_dts(kNoTimestamp);
if (is_pts_valid) {
int64_t pts = ConvertTimestampSectionToTimestamp(pts_section);
if (previous_pts_valid_)
pts = UnrollTimestamp(previous_pts_, pts);
previous_pts_ = pts;
previous_pts_valid_ = true;
media_pts = pts;
}
if (is_dts_valid) {
int64_t dts = ConvertTimestampSectionToTimestamp(dts_section);
if (previous_dts_valid_)
dts = UnrollTimestamp(previous_dts_, dts);
previous_dts_ = dts;
previous_dts_valid_ = true;
media_dts = dts;
}
// Discard the rest of the PES packet header.
DCHECK_EQ(bit_reader.bits_available() % 8, 0);
int pes_header_remaining_size = pes_header_data_length -
(pes_header_start_size - bit_reader.bits_available() / 8);
RCHECK(pes_header_remaining_size >= 0);
// Read the PES packet.
DVLOG(LOG_LEVEL_PES)
<< "Emit a reassembled PES:"
<< " size=" << es_size
<< " pts=" << media_pts
<< " dts=" << media_dts
<< " data_alignment_indicator=" << data_alignment_indicator;
return es_parser_->Parse(&raw_pes[es_offset], es_size, media_pts, media_dts);
}
void TsSectionPes::ResetPesState() {
pes_byte_queue_.Reset();
wait_for_pusi_ = true;
}
} // namespace mp2t
} // namespace media
} // namespace shaka