root/media/formats/mpeg/adts_stream_parser.cc

DEFINITIONS

1. ParseFrameHeader

// 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/mpeg/adts_stream_parser.h"

#include "media/formats/mpeg/adts_constants.h"

namespace media {

static const uint32 kADTSStartCodeMask = 0xfff00000;

ADTSStreamParser::ADTSStreamParser()
    : MPEGAudioStreamParserBase(kADTSStartCodeMask, kCodecAAC) {}

ADTSStreamParser::~ADTSStreamParser() {}

int ADTSStreamParser::ParseFrameHeader(const uint8* data,
                                       int size,
                                       int* frame_size,
                                       int* sample_rate,
                                       ChannelLayout* channel_layout,
                                       int* sample_count) const {
  DCHECK(data);
  DCHECK_GE(size, 0);
  DCHECK(frame_size);

  if (size < 8)
    return 0;

  BitReader reader(data, size);
  int sync;
  int version;
  int layer;
  int protection_absent;
  int profile;
  size_t sample_rate_index;
  size_t channel_layout_index;
  int frame_length;
  size_t num_data_blocks;
  int unused;

  if (!reader.ReadBits(12, &sync) ||
      !reader.ReadBits(1, &version) ||
      !reader.ReadBits(2, &layer) ||
      !reader.ReadBits(1, &protection_absent) ||
      !reader.ReadBits(2, &profile) ||
      !reader.ReadBits(4, &sample_rate_index) ||
      !reader.ReadBits(1, &unused) ||
      !reader.ReadBits(3, &channel_layout_index) ||
      !reader.ReadBits(4, &unused) ||
      !reader.ReadBits(13, &frame_length) ||
      !reader.ReadBits(11, &unused) ||
      !reader.ReadBits(2, &num_data_blocks) ||
      (!protection_absent && !reader.ReadBits(16, &unused))) {
    return -1;
  }

  DVLOG(2) << "Header data :" << std::hex
           << " sync 0x" << sync
           << " version 0x" << version
           << " layer 0x" << layer
           << " profile 0x" << profile
           << " sample_rate_index 0x" << sample_rate_index
           << " channel_layout_index 0x" << channel_layout_index;

  const int bytes_read = reader.bits_read() / 8;
  if (sync != 0xfff || layer != 0 || frame_length < bytes_read ||
      sample_rate_index >= kADTSFrequencyTableSize ||
      channel_layout_index >= kADTSChannelLayoutTableSize) {
    MEDIA_LOG(log_cb()) << "Invalid header data :" << std::hex
                        << " sync 0x" << sync
                        << " version 0x" << version
                        << " layer 0x" << layer
                        << " sample_rate_index 0x" << sample_rate_index
                        << " channel_layout_index 0x" << channel_layout_index;
    return -1;
  }

  if (sample_rate)
    *sample_rate = kADTSFrequencyTable[sample_rate_index];

  if (frame_size)
    *frame_size = frame_length;

  if (sample_count)
    *sample_count = (num_data_blocks + 1) * kSamplesPerAACFrame;

  if (channel_layout)
    *channel_layout = kADTSChannelLayoutTable[channel_layout_index];

  return bytes_read;
}

}  // namespace media