Mpeg2 TS stream parser for media source.

media/mpeg2/mpeg2ts_pes.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_pes.h"
+
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "media/base/bit_reader.h"
+#include "media/mpeg2/es_parser.h"
+#include "media/mpeg2/mpeg2ts_common.h"
+#include "media/mpeg2/mpeg2ts_def.h"
+
+namespace {
+
+int64 UnrollTimestamp(int64 previous_unrolled_time,
+                      int64 time,
+                      int nbits) {
+  // |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;
+  }
+  LOG_IF(INFO, unrolled_time != time1)
+      << "Unrolling time:"
+      << " previous_unrolled_time=" << previous_unrolled_time
+      << " time=" << time
+      << " unrolled_time=" << unrolled_time;
+
+  return unrolled_time;
+}
+
+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 one.
+  bool is_valid =
+      ((timestamp_section & 0x1) != 0) &&
+      ((timestamp_section & 0x10000) != 0) &&
+      ((timestamp_section & 0x100000000) != 0);
+  return is_valid;
+}
+
+int64 ConvertTimestampSectionToTimestamp(int64 timestamp_section) {
+  int64 timestamp =
+      (((timestamp_section >> 33) & 0x7) << 30) |
+      (((timestamp_section >> 17) & 0x7fff) << 15) |
+      (((timestamp_section >> 1) & 0x7fff) << 0);
+  return timestamp;
+}
+
+}  // namespace
+
+namespace media {
+namespace mpeg2ts {
+
+Mpeg2TsPesParser::Mpeg2TsPesParser(EsParser* es_parser)
+  : es_parser_(es_parser),
+    wait_for_unit_start_(true),
+    previous_pts_valid_(false),
+    previous_pts_(0),
+    previous_dts_valid_(false),
+    previous_dts_(0) {
+}
+
+Mpeg2TsPesParser::~Mpeg2TsPesParser() {
+}
+
+bool Mpeg2TsPesParser::Parse(bool payload_unit_start_indicator,
+                             const uint8* buf, int size) {
+  if (wait_for_unit_start_ && !payload_unit_start_indicator) {
+    // Ignore partial PES.
+    return true;
+  }
+  wait_for_unit_start_ = false;
+
+  if (payload_unit_start_indicator) {
+    // If we have a pending packet with an undefined size
+    // (size == 0), try to parse and emit the previous packet.
+    if (raw_pes_.size() > 0) {
+      // TODO(damienv): should check the result of InternalParse for a possible
+      // error.
+      InternalParse();
+      raw_pes_.resize(0);
+    }
+  }
+
+  // Add the data to the parser state.
+  if (size > 0) {
+    int old_size = raw_pes_.size();
+    raw_pes_.resize(old_size + size);
+    memcpy(&raw_pes_[old_size], buf, size);
+  }
+
+  // Check whether we have enough data to start parsing.
+  if (raw_pes_.size() < 6)
+    return true;
+  int pes_packet_length =
+      (static_cast<int>(raw_pes_[4]) << 8) |
+      (static_cast<int>(raw_pes_[5]));
+  VLOG(LOG_LEVEL_PES) << "pes_packet_length=" << pes_packet_length;
+  if (pes_packet_length == 0) {
+    // Video packets are emitted when a new unit is coming
+    // since there is no way to know the size of the packet before.
+    return true;
+  }
+  if (static_cast<int>(raw_pes_.size()) < pes_packet_length + 6) {
+    // Don't throw an error when there is not enough data,
+    // just wait for more data to come.
+    return true;
+  }
+
+  // Parse the packet.
+  bool parse_result = InternalParse();
+  raw_pes_.resize(0);
+  return parse_result;
+}
+
+void Mpeg2TsPesParser::Flush() {
+  // Force emitting the previous buffer by faking a
+  // payload_unit_start_indicator.
+  // For video, the pes packet length is set to 0,
+  // thus a video packet can only be emitted when the next video
+  // packet is coming.
+  Parse(true, NULL, 0);
+  raw_pes_.resize(0);
+
+  // Flush the underlying ES parser.
+  es_parser_->Flush();
+}
+
+bool Mpeg2TsPesParser::InternalParse() {
+  BitReader bit_reader(&raw_pes_[0], raw_pes_.size());
+  int remaining_size = raw_pes_.size();
+
+  // Read:
+  // - packet_start_code_prefix
+  // - stream_id
+  // - pes_packet_length
+  if (remaining_size < 6) {
+    return false;
+  }
+  int packet_start_code_prefix;
+  DCHECK(bit_reader.ReadBits(24, &packet_start_code_prefix));
+  if (packet_start_code_prefix != 0x000001) {
+    LOG(WARNING) << "Invalid PES start code: "
+                 << std::hex << "0x" << packet_start_code_prefix << std::dec;
+    return false;
+  }
+  int stream_id;
+  DCHECK(bit_reader.ReadBits(8, &stream_id));
+  VLOG(LOG_LEVEL_PES) << "stream_id=" << std::hex << stream_id << std::dec;
+  int pes_packet_length;
+  DCHECK(bit_reader.ReadBits(16, &pes_packet_length));
+  bool pes_packet_length_defined = (pes_packet_length != 0);
+  remaining_size -= 6;
+
+  if (stream_id != kProgramStreamMap &&
+      stream_id != kPaddingStream &&
+      stream_id != kPrivateStream2 &&
+      stream_id != kEcmStream &&
+      stream_id != kEmmStream &&
+      stream_id != kProgramStreamDirectory &&
+      stream_id != kDsmccStream &&
+      stream_id != kItu222TypeEStream) {
+    if (remaining_size < 3) {
+      return false;
+    }
+    int dummy_2;
+    DCHECK(bit_reader.ReadBits(2, &dummy_2));
+    if (dummy_2 != 0x2) {
+      LOG(WARNING) << "Unexpected bits";
+      return false;
+    }
+    int PES_scrambling_control;
+    DCHECK(bit_reader.ReadBits(2, &PES_scrambling_control));
+    bool PES_priority;
+    DCHECK(bit_reader.ReadBits(1, &PES_priority));
+    bool data_alignment_indicator;
+    DCHECK(bit_reader.ReadBits(1, &data_alignment_indicator));
+    bool copyright;
+    DCHECK(bit_reader.ReadBits(1, &copyright));
+    bool original_or_copy;
+    DCHECK(bit_reader.ReadBits(1, &original_or_copy));
+    int pts_dts_flags;
+    DCHECK(bit_reader.ReadBits(2, &pts_dts_flags));
+    bool escr_flag;
+    DCHECK(bit_reader.ReadBits(1, &escr_flag));
+    bool es_rate_flag;
+    DCHECK(bit_reader.ReadBits(1, &es_rate_flag));
+    bool dsm_trick_mode_flag;
+    DCHECK(bit_reader.ReadBits(1, &dsm_trick_mode_flag));
+    bool additional_copy_info_flag;
+    DCHECK(bit_reader.ReadBits(1, &additional_copy_info_flag));
+    bool pes_crc_flag;
+    DCHECK(bit_reader.ReadBits(1, &pes_crc_flag));
+    bool pes_extension_flag;
+    DCHECK(bit_reader.ReadBits(1, &pes_extension_flag));
+    int pes_header_data_length;
+    DCHECK(bit_reader.ReadBits(8, &pes_header_data_length));
+    remaining_size -= 3;
+    pes_packet_length -= 3;
+
+    bool is_pts_valid = false;
+    bool is_dts_valid = false;
+    int64 pts_section = 0;
+    int64 dts_section = 0;
+    if (pts_dts_flags == 0x2) {
+      if (remaining_size < 5) {
+        return false;
+      }
+      DCHECK(bit_reader.ReadBits(40, &pts_section));
+      if (((pts_section >> 36) & 0xf) != 0x2 ||
+          !IsTimestampSectionValid(pts_section)) {
+        LOG(WARNING) << "Invalid PTS section: "
+                     << std::hex << "0x" << pts_section << std::dec;
+        return false;
+      }
+      is_pts_valid = true;
+      remaining_size -= 5;
+      pes_packet_length -= 5;
+      pes_header_data_length -= 5;
+    }
+
+    if (pts_dts_flags == 0x3) {
+      if (remaining_size < 10) {
+        return false;
+      }
+      DCHECK(bit_reader.ReadBits(40, &pts_section));
+      if (((pts_section >> 36) & 0xf) != 0x3 ||
+          !IsTimestampSectionValid(pts_section)) {
+        LOG(WARNING) << "Invalid PTS section: "
+                     << std::hex << "0x" << pts_section << std::dec;
+        return false;
+      }
+      DCHECK(bit_reader.ReadBits(40, &dts_section));
+      if (((dts_section >> 36) & 0xf) != 0x1 ||
+          !IsTimestampSectionValid(dts_section)) {
+        LOG(WARNING) << "Invalid DTS section: "
+                     << std::hex << "0x" << dts_section << std::dec;
+        return false;
+      }
+      is_pts_valid = true;
+      is_dts_valid = true;
+      remaining_size -= 10;
+      pes_packet_length -= 10;
+      pes_header_data_length -= 10;
+    }
+
+    int64 pts = 0;
+    int64 dts = 0;
+    base::TimeDelta media_pts;
+    base::TimeDelta media_dts;
+    if (is_pts_valid) {
+      pts = ConvertTimestampSectionToTimestamp(pts_section);
+      if (previous_pts_valid_) {
+        pts = UnrollTimestamp(previous_pts_, pts, 33);
+      }
+      previous_pts_ = pts;
+      previous_pts_valid_ = true;
+      media_pts = base::TimeDelta::FromMicroseconds((1000 * pts) / 90);
+    }
+
+    if (is_dts_valid) {
+      dts = ConvertTimestampSectionToTimestamp(dts_section);
+      if (previous_dts_valid_) {
+        dts = UnrollTimestamp(previous_dts_, dts, 33);
+      }
+      previous_dts_ = dts;
+      previous_dts_valid_ = true;
+      media_dts = base::TimeDelta::FromMicroseconds((1000 * dts) / 90);
+    }
+
+    // TODO(damienv): check whether we need some info
+    // from the rest of the PES packet header.
+    if (pes_header_data_length < 0) {
+      LOG(WARNING) << "Invalid PES header length";
+      return false;
+    }
+    if (pes_header_data_length > 0) {
+      if (remaining_size < pes_header_data_length) {
+        return false;
+      }
+      for (int k = 0; k < pes_header_data_length; k++) {
+        int dummy;
+        DCHECK(bit_reader.ReadBits(8, &dummy));
+      }
+      remaining_size -= pes_header_data_length;
+      pes_packet_length -= pes_header_data_length;
+    }
+
+    // Read the PES packet.
+    if (pes_packet_length_defined && pes_packet_length < 0) {
+      LOG(WARNING) << "Invalid ES length: " << pes_packet_length;
+      return false;
+    }
+    int es_size = pes_packet_length;
+    if (!pes_packet_length_defined) {
+      es_size = remaining_size;
+    }
+    VLOG(LOG_LEVEL_PES)
+        << "Emit a reassembled PES:"
+        << " size=" << es_size
+        << " pts=" << pts
+        << " dts=" << dts
+        << " data_alignment_indicator=" << data_alignment_indicator;
+
+    int dump_count = 16;
+    if (es_size < 16)
+      dump_count = es_size;
+    int es_offset = raw_pes_.size() - remaining_size;
+    VLOG(LOG_LEVEL_PES)
+        << "=> " << base::HexEncode(&raw_pes_[es_offset], dump_count);
+    if (es_parser_) {
+      es_parser_->Parse(&raw_pes_[es_offset], es_size,
+                        is_pts_valid, media_pts,
+                        is_dts_valid, media_dts);
+    }
+    return true;
+  }
+
+  if (stream_id == kPaddingStream) {
+    return true;
+  }
+
+  // Handle the remaining stream ids.
+  VLOG(LOG_LEVEL_PES)
+      << "PES packet:"
+      << " size=" << pes_packet_length;
+  return true;
+}
+
+}  // namespace mpeg2ts
+}  // namespace media