root/media/formats/mp2t/es_parser_h264.cc

DEFINITIONS

1. next_access_unit_pos_
2. Flush
3. Reset
4. FindAUD
5. ParseInternal
6. EmitFrame
7. UpdateVideoDecoderConfig

// 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/es_parser_h264.h"

#include "base/basictypes.h"
#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "media/base/buffers.h"
#include "media/base/stream_parser_buffer.h"
#include "media/base/video_frame.h"
#include "media/filters/h264_parser.h"
#include "media/formats/common/offset_byte_queue.h"
#include "media/formats/mp2t/mp2t_common.h"
#include "ui/gfx/rect.h"
#include "ui/gfx/size.h"

namespace media {
namespace mp2t {

// An AUD NALU is at least 4 bytes:
// 3 bytes for the start code + 1 byte for the NALU type.
const int kMinAUDSize = 4;

EsParserH264::EsParserH264(
    const NewVideoConfigCB& new_video_config_cb,
    const EmitBufferCB& emit_buffer_cb)
  : new_video_config_cb_(new_video_config_cb),
    emit_buffer_cb_(emit_buffer_cb),
    es_queue_(new media::OffsetByteQueue()),
    h264_parser_(new H264Parser()),
    current_access_unit_pos_(0),
    next_access_unit_pos_(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 recommendation is to use one PES
  // for each access unit (but this is just a recommendation and some streams
  // do not comply with this recommendation).

  // HLS recommendation: "In AVC video, you should have both a DTS and a
  // PTS in each PES header".
  // However, some streams do not comply with this recommendation.
  DVLOG_IF(1, pts == kNoTimestamp()) << "Each video PES should have a PTS";
  if (pts != kNoTimestamp()) {
    TimingDesc timing_desc;
    timing_desc.pts = pts;
    timing_desc.dts = (dts != kNoTimestamp()) ? dts : pts;

    // Link the end of the byte queue with the incoming timing descriptor.
    timing_desc_list_.push_back(
        std::pair<int64, TimingDesc>(es_queue_->tail(), timing_desc));
  }

  // Add the incoming bytes to the ES queue.
  es_queue_->Push(buf, size);
  return ParseInternal();
}

void EsParserH264::Flush() {
  DVLOG(1) << "EsParserH264::Flush";
  if (!FindAUD(&current_access_unit_pos_))
    return;

  // Simulate an additional AUD to force emitting the last access unit
  // which is assumed to be complete at this point.
  uint8 aud[] = { 0x00, 0x00, 0x01, 0x09 };
  es_queue_->Push(aud, sizeof(aud));
  ParseInternal();
}

void EsParserH264::Reset() {
  DVLOG(1) << "EsParserH264::Reset";
  es_queue_.reset(new media::OffsetByteQueue());
  h264_parser_.reset(new H264Parser());
  current_access_unit_pos_ = 0;
  next_access_unit_pos_ = 0;
  timing_desc_list_.clear();
  last_video_decoder_config_ = VideoDecoderConfig();
}

bool EsParserH264::FindAUD(int64* stream_pos) {
  while (true) {
    const uint8* es;
    int size;
    es_queue_->PeekAt(*stream_pos, &es, &size);

    // Find a start code and move the stream to the start code parser position.
    off_t start_code_offset;
    off_t start_code_size;
    bool start_code_found = H264Parser::FindStartCode(
        es, size, &start_code_offset, &start_code_size);
    *stream_pos += start_code_offset;

    // No H264 start code found or NALU type not available yet.
    if (!start_code_found || start_code_offset + start_code_size >= size)
      return false;

    // Exit the parser loop when an AUD is found.
    // Note: NALU header for an AUD:
    // - nal_ref_idc must be 0
    // - nal_unit_type must be H264NALU::kAUD
    if (es[start_code_offset + start_code_size] == H264NALU::kAUD)
      break;

    // The current NALU is not an AUD, skip the start code
    // and continue parsing the stream.
    *stream_pos += start_code_size;
  }

  return true;
}

bool EsParserH264::ParseInternal() {
  DCHECK_LE(es_queue_->head(), current_access_unit_pos_);
  DCHECK_LE(current_access_unit_pos_, next_access_unit_pos_);
  DCHECK_LE(next_access_unit_pos_, es_queue_->tail());

  // Find the next AUD located at or after |current_access_unit_pos_|. This is
  // needed since initially |current_access_unit_pos_| might not point to
  // an AUD.
  // Discard all the data before the updated |current_access_unit_pos_|
  // since it won't be used again.
  bool aud_found = FindAUD(&current_access_unit_pos_);
  es_queue_->Trim(current_access_unit_pos_);
  if (next_access_unit_pos_ < current_access_unit_pos_)
    next_access_unit_pos_ = current_access_unit_pos_;

  // Resume parsing later if no AUD was found.
  if (!aud_found)
    return true;

  // Find the next AUD to make sure we have a complete access unit.
  if (next_access_unit_pos_ < current_access_unit_pos_ + kMinAUDSize) {
    next_access_unit_pos_ = current_access_unit_pos_ + kMinAUDSize;
    DCHECK_LE(next_access_unit_pos_, es_queue_->tail());
  }
  if (!FindAUD(&next_access_unit_pos_))
    return true;

  // At this point, we know we have a full access unit.
  bool is_key_frame = false;
  int pps_id_for_access_unit = -1;

  const uint8* es;
  int size;
  es_queue_->PeekAt(current_access_unit_pos_, &es, &size);
  int access_unit_size = base::checked_cast<int, int64>(
      next_access_unit_pos_ - current_access_unit_pos_);
  DCHECK_LE(access_unit_size, size);
  h264_parser_->SetStream(es, access_unit_size);

  while (true) {
    bool is_eos = false;
    H264NALU nalu;
    switch (h264_parser_->AdvanceToNextNALU(&nalu)) {
      case H264Parser::kOk:
        break;
      case H264Parser::kInvalidStream:
      case H264Parser::kUnsupportedStream:
        return false;
      case H264Parser::kEOStream:
        is_eos = true;
        break;
    }
    if (is_eos)
      break;

    switch (nalu.nal_unit_type) {
      case H264NALU::kAUD: {
        DVLOG(LOG_LEVEL_ES) << "NALU: AUD";
        break;
      }
      case H264NALU::kSPS: {
        DVLOG(LOG_LEVEL_ES) << "NALU: SPS";
        int sps_id;
        if (h264_parser_->ParseSPS(&sps_id) != H264Parser::kOk)
          return false;
        break;
      }
      case H264NALU::kPPS: {
        DVLOG(LOG_LEVEL_ES) << "NALU: PPS";
        int pps_id;
        if (h264_parser_->ParsePPS(&pps_id) != H264Parser::kOk)
          return false;
        break;
      }
      case H264NALU::kIDRSlice:
      case H264NALU::kNonIDRSlice: {
        is_key_frame = (nalu.nal_unit_type == H264NALU::kIDRSlice);
        DVLOG(LOG_LEVEL_ES) << "NALU: slice IDR=" << is_key_frame;
        H264SliceHeader shdr;
        if (h264_parser_->ParseSliceHeader(nalu, &shdr) != H264Parser::kOk) {
          // Only accept an invalid SPS/PPS at the beginning when the stream
          // does not necessarily start with an SPS/PPS/IDR.
          // TODO(damienv): Should be able to differentiate a missing SPS/PPS
          // from a slice header parsing error.
          if (last_video_decoder_config_.IsValidConfig())
            return false;
        } else {
          pps_id_for_access_unit = shdr.pic_parameter_set_id;
        }
        break;
      }
      default: {
        DVLOG(LOG_LEVEL_ES) << "NALU: " << nalu.nal_unit_type;
      }
    }
  }

  // Emit a frame and move the stream to the next AUD position.
  RCHECK(EmitFrame(current_access_unit_pos_, access_unit_size,
                   is_key_frame, pps_id_for_access_unit));
  current_access_unit_pos_ = next_access_unit_pos_;
  es_queue_->Trim(current_access_unit_pos_);

  return true;
}

bool EsParserH264::EmitFrame(int64 access_unit_pos, int access_unit_size,
                             bool is_key_frame, int pps_id) {
  // Get the access unit timing info.
  TimingDesc current_timing_desc = {kNoTimestamp(), kNoTimestamp()};
  while (!timing_desc_list_.empty() &&
         timing_desc_list_.front().first <= access_unit_pos) {
    current_timing_desc = timing_desc_list_.front().second;
    timing_desc_list_.pop_front();
  }
  if (current_timing_desc.pts == kNoTimestamp())
    return false;

  // Update the video decoder configuration if needed.
  const H264PPS* pps = h264_parser_->GetPPS(pps_id);
  if (!pps) {
    // Only accept an invalid PPS at the beginning when the stream
    // does not necessarily start with an SPS/PPS/IDR.
    // In this case, the initial frames are conveyed to the upper layer with
    // an invalid VideoDecoderConfig and it's up to the upper layer
    // to process this kind of frame accordingly.
    if (last_video_decoder_config_.IsValidConfig())
      return false;
  } else {
    const H264SPS* sps = h264_parser_->GetSPS(pps->seq_parameter_set_id);
    if (!sps)
      return false;
    RCHECK(UpdateVideoDecoderConfig(sps));
  }

  // Emit a frame.
  DVLOG(LOG_LEVEL_ES) << "Emit frame: stream_pos=" << current_access_unit_pos_
                      << " size=" << access_unit_size;
  int es_size;
  const uint8* es;
  es_queue_->PeekAt(current_access_unit_pos_, &es, &es_size);
  CHECK_GE(es_size, access_unit_size);

  // TODO(wolenetz/acolwell): Validate and use a common cross-parser TrackId
  // type and allow multiple video tracks. See https://crbug.com/341581.
  scoped_refptr<StreamParserBuffer> stream_parser_buffer =
      StreamParserBuffer::CopyFrom(
          es,
          access_unit_size,
          is_key_frame,
          DemuxerStream::VIDEO,
          0);
  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;
}

bool EsParserH264::UpdateVideoDecoderConfig(const H264SPS* sps) {
  // Set the SAR to 1 when not specified in the H264 stream.
  int sar_width = (sps->sar_width == 0) ? 1 : sps->sar_width;
  int sar_height = (sps->sar_height == 0) ? 1 : sps->sar_height;

  // 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((sps->pic_width_in_mbs_minus1 + 1) * 16,
                       (sps->pic_height_in_map_units_minus1 + 1) * 16);
  gfx::Rect visible_rect(
      sps->frame_crop_left_offset,
      sps->frame_crop_top_offset,
      (coded_size.width() - sps->frame_crop_right_offset) -
      sps->frame_crop_left_offset,
      (coded_size.height() - sps->frame_crop_bottom_offset) -
      sps->frame_crop_top_offset);
  if (visible_rect.width() <= 0 || visible_rect.height() <= 0)
    return false;
  gfx::Size natural_size(
      (visible_rect.width() * sar_width) / sar_height,
      visible_rect.height());
  if (natural_size.width() == 0)
    return false;

  VideoDecoderConfig video_decoder_config(
      kCodecH264,
      VIDEO_CODEC_PROFILE_UNKNOWN,
      VideoFrame::YV12,
      coded_size,
      visible_rect,
      natural_size,
      NULL, 0,
      false);

  if (!video_decoder_config.Matches(last_video_decoder_config_)) {
    DVLOG(1) << "Profile IDC: " << sps->profile_idc;
    DVLOG(1) << "Level IDC: " << sps->level_idc;
    DVLOG(1) << "Pic width: " << coded_size.width();
    DVLOG(1) << "Pic height: " << coded_size.height();
    DVLOG(1) << "log2_max_frame_num_minus4: "
             << sps->log2_max_frame_num_minus4;
    DVLOG(1) << "SAR: width=" << sps->sar_width
             << " height=" << sps->sar_height;
    last_video_decoder_config_ = video_decoder_config;
    new_video_config_cb_.Run(video_decoder_config);
  }

  return true;
}

}  // namespace mp2t
}  // namespace media