Mpeg2 TS stream parser for media source.

media/mp2t/es_parser_h264.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/mp2t/es_parser_h264.h"
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/base/buffers.h"
+#include "media/base/stream_parser_buffer.h"
+#include "media/base/video_decoder_config.h"
+#include "media/base/video_frame.h"
+#include "media/mp2t/mp2t_common.h"
+#include "ui/gfx/rect.h"
+#include "ui/gfx/size.h"
+
+static const int kExtendedSar = 255;
+
+static const int kTableSarWidth[14] = {
+  1, 1, 12, 10, 16, 40, 24, 20, 32, 80, 18, 15, 64, 160
+};
+
+static const int kTableSarHeight[14] = {
+  1, 1, 11, 11, 11, 33, 11, 11, 11, 33, 11, 11, 33, 99
+};
+
+namespace media {
+namespace mp2t {
+
+class BitReaderH264 : public BitReader {
+ public:
+  BitReaderH264(const uint8* data, off_t size)
+    : BitReader(data, size) { }
+
+  // Read an unsigned exp-golomb value.
+  // Return true if successful.
+  bool ReadBitsExpGolomb(uint32* exp_golomb_value);
+};
+
+bool BitReaderH264::ReadBitsExpGolomb(uint32* exp_golomb_value) {
+  // Get the number of leading zeros.
+  int zero_count = 0;
+  while (true) {
+    int one_bit;
+    RCHECK(ReadBits(1, &one_bit));
+    if (one_bit != 0)
+      break;
+    zero_count++;
+  }
+
+  // If zero_count is greater than 31, the calculated value will overflow.
+  if (zero_count > 31) {
+    SkipBits(zero_count);
+    return false;
+  }

[damienv1, 2013/09/12 20:43:02]

TODO: special case if |zero_count| = 0 ?

+
+  // Read the actual value.
+  uint32 base = (1 << zero_count) - 1;
+  uint32 offset;
+  RCHECK(ReadBits(zero_count, &offset));
+  *exp_golomb_value = base + offset;
+
+  return true;
+}
+
+EsParserH264::EsParserH264(
+    NewVideoConfigCB new_video_config_cb,
+    EmitBufferCB emit_buffer_cb)
+  : nal_es_pos_(0),
+    new_video_config_cb_(new_video_config_cb),
+    emit_buffer_cb_(emit_buffer_cb),
+    is_video_config_known_(false),
+    profile_idc_(0),
+    level_idc_(0),
+    pic_width_in_mbs_minus1_(0),
+    pic_height_in_map_units_minus1_(0) {
+}
+
+EsParserH264::~EsParserH264() {
+}
+
+bool EsParserH264::Parse(const uint8* buf, int size,
+                         base::TimeDelta pts,
+                         base::TimeDelta dts) {
+  // Note: Parse is invoked each time a PES packet has been reassembled.
+  // Unfortunately, a PES packet does not necessarily map
+  // to an h264 access unit, although the HLS recommandation is to use one PES
+  // for each access unit (but this is just a recommandation and some streams
+  // do not comply with this recommandation).
+
+  // Link position |raw_es_size| in the ES stream with a timing descriptor.
+  // HLS recommandation: "In AVC video, you should have both a DTS and a
+  // PTS in each PES header".
+  if (dts == kNoTimestamp() && pts == kNoTimestamp()) {
+    DVLOG(1) << "A timestamp must be provided for each reassembled PES";
+    Reset();
+    return false;
+  }
+  TimingDesc timing_desc;
+  timing_desc.pts = pts;
+  timing_desc.dts = (dts != kNoTimestamp()) ? dts : pts;
+
+  int raw_es_size;
+  const uint8* raw_es;
+  es_byte_queue_.Peek(&raw_es, &raw_es_size);
+  timing_desc_list_.push_back(
+      std::pair<int, TimingDesc>(raw_es_size, timing_desc));
+
+  // Add the incoming bytes to the ES queue.
+  es_byte_queue_.Push(buf, size);
+  es_byte_queue_.Peek(&raw_es, &raw_es_size);
+
+  // Add NALs from the incoming buffer.
+  FindNals();
+
+  // Find access units based on AUD.
+  std::list<NalDescList::const_iterator> access_unit_list;
+  FindAccessUnits(&access_unit_list);
+  if (access_unit_list.empty()) {
+    DiscardEs(nal_es_pos_);
+    return true;
+  }
+
+  // Emit all frames.
+  std::list<NalDescList::const_iterator>::iterator it0 =
+      access_unit_list.begin();
+  std::list<NalDescList::const_iterator>::iterator it1 = it0;
+  ++it1;
+  LOG_IF(WARNING, (*it0)->position != 0)
+      << "Needs to discard some ES data before getting the 1st access unit: "
+      << (*it0)->position;
+  for (; it1 != access_unit_list.end(); ++it0, ++it1) {
+    int nxt_frame_position = (*it1)->position;
+    bool status = EmitFrame(*it0, *it1, nxt_frame_position);
+    if (!status) {
+      Reset();
+      return false;
+    }
+  }
+
+  // Discard emitted frames.
+  int last_position = access_unit_list.back()->position;
+  DiscardEs(last_position);
+
+  return true;
+}
+
+void EsParserH264::Flush() {
+  // Find access units based on AUD.
+  std::list<NalDescList::const_iterator> access_unit_list;
+  FindAccessUnits(&access_unit_list);
+
+  // At this point, there can be at most one access unit in the buffer.
+  DCHECK_GE(access_unit_list.size(), 1u);
+  if (!access_unit_list.empty()) {
+    // Force emitting the last access unit (even if it might be incomplete).
+    int nxt_frame_position = 0;
+    const uint8* raw_es = NULL;
+    es_byte_queue_.Peek(&raw_es, &nxt_frame_position);
+    NalDescList::const_iterator cur_frame = *(access_unit_list.begin());
+    NalDescList::const_iterator nxt_frame = nal_desc_list_.end();
+    EmitFrame(cur_frame, nxt_frame, nxt_frame_position);
+  }
+}
+
+void EsParserH264::Reset() {
+  DVLOG(1) << "EsParserH264::Reset";
+  es_byte_queue_.Reset();
+  timing_desc_list_.clear();
+  nal_desc_list_.clear();
+  nal_es_pos_ = 0;
+  is_video_config_known_ = false;
+}
+
+void EsParserH264::FindNals() {
+  int raw_es_size;
+  const uint8* raw_es;
+  es_byte_queue_.Peek(&raw_es, &raw_es_size);
+
+  DCHECK_GE(nal_es_pos_, 0);
+  DCHECK_LT(nal_es_pos_, raw_es_size);
+
+  // Resume NAL segmentation where it was left.
+  for ( ; nal_es_pos_ < raw_es_size - 4; nal_es_pos_++) {
+    // Make sure the syncword is either 00 00 00 01 or 00 00 01
+    if (raw_es[nal_es_pos_ + 0] != 0 ||
+        raw_es[nal_es_pos_ + 1] != 0) {
+      continue;
+    }
+    int syncword_length = 0;
+    if (raw_es[nal_es_pos_ + 2] == 0 &&
+        raw_es[nal_es_pos_ + 3] == 1) {
+      syncword_length = 4;
+    } else if (raw_es[nal_es_pos_ + 2] == 1) {
+      syncword_length = 3;
+    } else {
+      continue;
+    }
+
+    // Retrieve the NAL type.
+    int nal_header = raw_es[nal_es_pos_ + syncword_length];
+    int forbidden_zero_bit = (nal_header >> 7) & 0x1;
+    NalDesc nal_desc;
+    nal_desc.position = nal_es_pos_;
+    nal_desc.nal_unit_type = static_cast<NalUnitType>(nal_header & 0x1f);
+    if (forbidden_zero_bit != 0)
+      nal_desc.nal_unit_type = kNalUnitTypeInvalid;
+    DVLOG(LOG_LEVEL_ES) << "nal: offset=" << nal_desc.position
+                        << " type=" << nal_desc.nal_unit_type;
+    nal_desc_list_.push_back(nal_desc);
+    nal_es_pos_ += syncword_length;
+  }
+}
+
+void EsParserH264::FindAccessUnits(
+    std::list<NalDescList::const_iterator>* access_unit_list) {
+  // Get the H264 access units based on AUD.
+  // Mpeg2TS spec: "2.14 Carriage of Rec. ITU-T H.264 | ISO/IEC 14496-10 video"
+  // "Each AVC access unit shall contain an access unit delimiter NAL Unit;"
+  for (NalDescList::const_iterator it = nal_desc_list_.begin();
+       it != nal_desc_list_.end(); ++it) {
+    if (it->nal_unit_type == kNalUnitTypeAUD) {
+      DVLOG(LOG_LEVEL_ES) << "aud found @ pos=" << it->position;
+      access_unit_list->push_back(it);
+    }
+  }
+}
+
+bool EsParserH264::EmitFrame(
+    NalDescList::const_iterator& cur_frame,
+    NalDescList::const_iterator& nxt_frame,
+    int nxt_frame_position) {
+  int raw_es_size;
+  const uint8* raw_es;
+  es_byte_queue_.Peek(&raw_es, &raw_es_size);
+
+  // Current frame position = position of the 1st NAL of the frame.
+  int cur_frame_position = cur_frame->position;
+  int access_unit_size = nxt_frame_position - cur_frame_position;
+
+  // Get the access unit timing info.
+  TimingDesc current_timing_desc;
+  while (!timing_desc_list_.empty() &&
+         timing_desc_list_.front().first <= cur_frame_position) {
+    current_timing_desc = timing_desc_list_.front().second;
+    timing_desc_list_.pop_front();
+  }
+
+  // Check whether this is a key frame + light NAL parsing to get some
+  // relevant information (e.g. SPS/PPS).
+  // Note: it would have been nice to get the keyframe decision based
+  // on the Mpeg2TS random_access_indicator but encoders sometimes just don't
+  // bother setting this flag in the MPEG2 TS stream.
+  bool is_key_frame = true;
+  for (NalDescList::const_iterator it = cur_frame; it != nxt_frame; ++it) {
+    if (it->nal_unit_type == kNalUnitTypeNonIdrSlice)
+      is_key_frame = false;
+    NalDescList::const_iterator next_nal_it = it;
+    ++next_nal_it;
+    int cur_nal_position = it->position;
+    int nxt_nal_position = (next_nal_it == nxt_frame)
+        ? nxt_frame_position : next_nal_it->position;
+    int nal_size = nxt_nal_position - cur_nal_position;
+    DCHECK_LE(cur_nal_position + nal_size, raw_es_size);
+    bool nal_status = NalParser(&raw_es[cur_nal_position], nal_size);
+    if (!nal_status)
+      return false;
+  }
+
+  // Emit the current frame.
+  DVLOG(LOG_LEVEL_ES) << "is_key_frame = " << is_key_frame;
+  scoped_refptr<StreamParserBuffer> stream_parser_buffer =
+      StreamParserBuffer::CopyFrom(
+          &raw_es[cur_frame_position],
+          access_unit_size,
+          is_key_frame);
+  stream_parser_buffer->SetDecodeTimestamp(current_timing_desc.dts);
+  stream_parser_buffer->set_timestamp(current_timing_desc.pts);
+  emit_buffer_cb_.Run(stream_parser_buffer);
+
+  return true;
+}
+
+void EsParserH264::DiscardEs(int nbytes) {
+  if (nbytes <= 0)
+    return;
+
+  // Update the NAL list accordingly.
+  while (!nal_desc_list_.empty() &&
+         nal_desc_list_.front().position < nbytes)
+    nal_desc_list_.pop_front();
+  for (NalDescList::iterator it = nal_desc_list_.begin();
+       it != nal_desc_list_.end(); ++it) {
+    DCHECK(it->position >= nbytes);
+    it->position -= nbytes;
+  }
+  nal_es_pos_ -= nbytes;
+  if (nal_es_pos_ < 0)
+    nal_es_pos_ = 0;
+
+  // Update the timing information accordingly.
+  std::list<std::pair<int, TimingDesc> >::iterator timing_it
+      = timing_desc_list_.begin();
+  for (; timing_it != timing_desc_list_.end(); ++timing_it)
+    timing_it->first -= nbytes;
+
+  // Discard |nbytes| of ES.
+  es_byte_queue_.Pop(nbytes);
+}
+
+bool EsParserH264::NalParser(const uint8* buf, int size) {
+  // Discard the annexB syncword.
+  if (size < 3 || buf[0] != 0 || buf[1] != 0 ||
+      !(buf[2] == 1 || (size >= 4 && buf[2] == 0 && buf[3] == 1))) {
+    DVLOG(1) << "NalParser: bad annexB start code";
+    return false;
+  }
+  if (buf[2] == 1) {
+    buf += 3;
+    size -= 3;
+  } else {
+    buf += 4;
+    size -= 4;
+  }
+
+  // Get the NAL header.
+  if (size < 1) {
+    DVLOG(1) << "NalParser: incomplete NAL";
+    return false;
+  }
+  int nal_header = buf[0];
+  buf += 1;
+  size -= 1;
+
+  int forbidden_zero_bit = (nal_header >> 7) & 0x1;
+  if (forbidden_zero_bit != 0)
+    return false;
+  int nal_ref_idc = (nal_header >> 5) & 0x3;
+  int nal_unit_type = nal_header & 0x1f;
+
+  // TODO(damienv):
+  // The nal start code emulation prevention should be un-done,
+  // before parsing the NAL content.
+
+  // Process the NAL content.
+  if (nal_unit_type == kNalUnitTypeSPS) {
+    DVLOG(LOG_LEVEL_ES) << "NAL: SPS";
+    // |nal_ref_idc| should not be 0 for a SPS.
+    if (nal_ref_idc == 0)
+      return false;
+    return ProcessSPS(buf, size);
+  }
+  if (nal_unit_type == kNalUnitTypeIdrSlice) {
+    DVLOG(LOG_LEVEL_ES) << "NAL: IDR slice";
+    return true;
+  }
+  if (nal_unit_type == kNalUnitTypeNonIdrSlice) {
+    DVLOG(LOG_LEVEL_ES) << "NAL: Non IDR slice";
+    return true;
+  }
+  if (nal_unit_type == kNalUnitTypePPS) {
+    DVLOG(LOG_LEVEL_ES) << "NAL: PPS";
+    return true;
+  }
+  if (nal_unit_type == kNalUnitTypeAUD) {
+    DVLOG(LOG_LEVEL_ES) << "NAL: AUD";
+    return true;
+  }
+
+  DVLOG(LOG_LEVEL_ES) << "NAL: " << nal_unit_type;
+  return true;
+}
+
+bool EsParserH264::ProcessSPS(const uint8* buf, int size) {
+  if (size <= 0)
+    return false;
+  BitReaderH264 bit_reader(buf, size);
+
+  int profile_idc;
+  int constraint_setX_flag;
+  int level_idc;
+  uint32 seq_parameter_set_id;
+  uint32 log2_max_frame_num_minus4;
+  uint32 pic_order_cnt_type;
+  RCHECK(bit_reader.ReadBits(8, &profile_idc));
+  RCHECK(bit_reader.ReadBits(8, &constraint_setX_flag));
+  RCHECK(bit_reader.ReadBits(8, &level_idc));
+  RCHECK(bit_reader.ReadBitsExpGolomb(&seq_parameter_set_id));
+  RCHECK(bit_reader.ReadBitsExpGolomb(&log2_max_frame_num_minus4));
+  RCHECK(bit_reader.ReadBitsExpGolomb(&pic_order_cnt_type));
+
+  // |pic_order_cnt_type| shall be in the range of 0 to 2.
+  if (pic_order_cnt_type > 2)
+    return false;
+  if (pic_order_cnt_type == 0) {
+    uint32 log2_max_pic_order_cnt_lsb_minus4;
+    RCHECK(bit_reader.ReadBitsExpGolomb(&log2_max_pic_order_cnt_lsb_minus4));
+  } else if (pic_order_cnt_type == 1) {
+    NOTIMPLEMENTED();
+    return false;
+  }
+
+  uint32 num_ref_frames;
+  int gaps_in_frame_num_value_allowed_flag;
+  uint32 pic_width_in_mbs_minus1;
+  uint32 pic_height_in_map_units_minus1;
+  RCHECK(bit_reader.ReadBitsExpGolomb(&num_ref_frames));
+  RCHECK(bit_reader.ReadBits(1, &gaps_in_frame_num_value_allowed_flag));
+  RCHECK(bit_reader.ReadBitsExpGolomb(&pic_width_in_mbs_minus1));
+  RCHECK(bit_reader.ReadBitsExpGolomb(&pic_height_in_map_units_minus1));
+
+  int frame_mbs_only_flag;
+  RCHECK(bit_reader.ReadBits(1, &frame_mbs_only_flag));
+  if (!frame_mbs_only_flag) {
+    int mb_adaptive_frame_field_flag;
+    RCHECK(bit_reader.ReadBits(1, &mb_adaptive_frame_field_flag));
+  }
+
+  int direct_8x8_inference_flag;
+  RCHECK(bit_reader.ReadBits(1, &direct_8x8_inference_flag));
+
+  bool frame_cropping_flag;
+  uint32 frame_crop_left_offset = 0;
+  uint32 frame_crop_right_offset = 0;
+  uint32 frame_crop_top_offset = 0;
+  uint32 frame_crop_bottom_offset = 0;
+  RCHECK(bit_reader.ReadBits(1, &frame_cropping_flag));
+  if (frame_cropping_flag) {
+    RCHECK(bit_reader.ReadBitsExpGolomb(&frame_crop_left_offset));
+    RCHECK(bit_reader.ReadBitsExpGolomb(&frame_crop_right_offset));
+    RCHECK(bit_reader.ReadBitsExpGolomb(&frame_crop_top_offset));
+    RCHECK(bit_reader.ReadBitsExpGolomb(&frame_crop_bottom_offset));
+  }
+
+  bool vui_parameters_present_flag;
+  RCHECK(bit_reader.ReadBits(1, &vui_parameters_present_flag));
+  int sar_width = 1;
+  int sar_height = 1;
+  if (vui_parameters_present_flag) {
+    // Read only the aspect ratio information from the VUI section.
+    // TODO(damienv): check whether other VUI info are useful.
+    bool aspect_ratio_info_present_flag = false;
+    RCHECK(bit_reader.ReadBits(1, &aspect_ratio_info_present_flag));
+    if (aspect_ratio_info_present_flag) {
+      int aspect_ratio_idc;
+      RCHECK(bit_reader.ReadBits(8, &aspect_ratio_idc));
+      if (aspect_ratio_idc == kExtendedSar) {
+        RCHECK(bit_reader.ReadBits(16, &sar_width));
+        RCHECK(bit_reader.ReadBits(16, &sar_height));
+      } else if (aspect_ratio_idc < 14) {
+        sar_width = kTableSarWidth[aspect_ratio_idc];
+        sar_height = kTableSarHeight[aspect_ratio_idc];
+      }
+    }
+  }
+
+  if (sar_width != sar_height) {
+    // TODO(damienv): Support non square pixels.
+    DVLOG(1)
+      << "Non square pixel not supported yet:"
+      << " sar_width=" << sar_width
+      << " sar_height=" << sar_height;
+    return false;
+  }
+
+  if (is_video_config_known_ &&
+      profile_idc == profile_idc_ &&
+      level_idc == level_idc_ &&
+      pic_width_in_mbs_minus1 == pic_width_in_mbs_minus1_ &&
+      pic_height_in_map_units_minus1 == pic_height_in_map_units_minus1_) {
+    // This is the same SPS as the previous one.
+    return true;
+  }
+  is_video_config_known_ = true;
+  profile_idc_ = profile_idc;
+  level_idc_ = level_idc;
+  pic_width_in_mbs_minus1_ = pic_width_in_mbs_minus1;
+  pic_height_in_map_units_minus1_ = pic_height_in_map_units_minus1;
+
+  // TODO(damienv):
+  // Assuming the SPS is used right away by the PPS
+  // and the slice headers is a strong assumption.
+  // In theory, we should process the SPS and PPS
+  // and only when one of the slice header is switching
+  // the PPS id, the video decoder config should be changed.
+  DVLOG(1) << "Profile IDC: " << profile_idc;
+  DVLOG(1) << "Level IDC: " << level_idc;
+  DVLOG(1) << "Pic width: " << (pic_width_in_mbs_minus1 + 1) * 16;
+  DVLOG(1) << "Pic height: " << (pic_height_in_map_units_minus1 + 1) * 16;
+  DVLOG(1) << "log2_max_frame_num_minus4: " << log2_max_frame_num_minus4;
+
+  // TODO(damienv): a MAP unit can be either 16 or 32 pixels.
+  // although it's 16 pixels for progressive non MBAFF frames.
+  gfx::Size coded_size((pic_width_in_mbs_minus1 + 1) * 16,
+                       (pic_height_in_map_units_minus1 + 1) * 16);
+  gfx::Rect visible_rect(
+      frame_crop_left_offset,
+      frame_crop_top_offset,
+      (coded_size.width() - frame_crop_right_offset) - frame_crop_left_offset,
+      (coded_size.height() - frame_crop_bottom_offset) - frame_crop_top_offset);
+
+  // TODO(damienv): calculate the natural size based
+  // on the possible aspect ratio coded in the VUI parameters.
+  gfx::Size natural_size(visible_rect.width(),
+                         visible_rect.height());
+
+  VideoDecoderConfig video_decoder_config(
+      kCodecH264,
+      VIDEO_CODEC_PROFILE_UNKNOWN,    // TODO(damienv)
+      VideoFrame::YV12,
+      coded_size,
+      visible_rect,
+      natural_size,
+      NULL, 0,
+      false);
+  new_video_config_cb_.Run(video_decoder_config);
+
+  return true;
+}
+
+}  // namespace mp2t
+}  // namespace media
+