diff options
Diffstat (limited to 'media/formats/mp2t/ts_section_pes.cc')
| -rw-r--r-- | media/formats/mp2t/ts_section_pes.cc | 312 |
1 files changed, 312 insertions, 0 deletions
diff --git a/media/formats/mp2t/ts_section_pes.cc b/media/formats/mp2t/ts_section_pes.cc new file mode 100644 index 0000000..de69a32 --- /dev/null +++ b/media/formats/mp2t/ts_section_pes.cc @@ -0,0 +1,312 @@ +// 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_section_pes.h" + +#include "base/logging.h" +#include "base/strings/string_number_conversions.h" +#include "media/base/bit_reader.h" +#include "media/base/buffers.h" +#include "media/formats/mp2t/es_parser.h" +#include "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 UnrollTimestamp(int64 previous_unrolled_time, int64 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 previous_unrolled_time_high = + (previous_unrolled_time >> nbits); + int64 time0 = ((previous_unrolled_time_high - 1) << nbits) | time; + int64 time1 = ((previous_unrolled_time_high + 0) << nbits) | time; + int64 time2 = ((previous_unrolled_time_high + 1) << nbits) | time; + + // Select the min absolute difference with the current time + // so as to ensure time continuity. + int64 diff0 = time0 - previous_unrolled_time; + int64 diff1 = time1 - previous_unrolled_time; + int64 diff2 = time2 - previous_unrolled_time; + if (diff0 < 0) + diff0 = -diff0; + if (diff1 < 0) + diff1 = -diff1; + if (diff2 < 0) + diff2 = -diff2; + + int64 unrolled_time; + int64 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 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 & 0x100000000) != 0); +} + +static int64 ConvertTimestampSectionToTimestamp(int64 timestamp_section) { + return (((timestamp_section >> 33) & 0x7) << 30) | + (((timestamp_section >> 17) & 0x7fff) << 15) | + (((timestamp_section >> 1) & 0x7fff) << 0); +} + +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* 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* 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* 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* 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 pts_section = 0; + int64 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. + base::TimeDelta media_pts(kNoTimestamp()); + base::TimeDelta media_dts(kNoTimestamp()); + if (is_pts_valid) { + int64 pts = ConvertTimestampSectionToTimestamp(pts_section); + if (previous_pts_valid_) + pts = UnrollTimestamp(previous_pts_, pts); + previous_pts_ = pts; + previous_pts_valid_ = true; + media_pts = base::TimeDelta::FromMicroseconds((1000 * pts) / 90); + } + if (is_dts_valid) { + int64 dts = ConvertTimestampSectionToTimestamp(dts_section); + if (previous_dts_valid_) + dts = UnrollTimestamp(previous_dts_, dts); + previous_dts_ = dts; + previous_dts_valid_ = true; + media_dts = base::TimeDelta::FromMicroseconds((1000 * dts) / 90); + } + + // Discard the rest of the PES packet header. + // TODO(damienv): check if some info of the PES packet header are useful. + 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.InMilliseconds() + << " dts=" << media_dts.InMilliseconds() + << " 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 + |