media/mp4/aac.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_MP4_AAC_H_
   6 #define MEDIA_MP4_AAC_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "media/base/channel_layout.h"
  12 #include "media/base/media_export.h"
  13
  14 namespace media {
  15
  16 class BitReader;
  17
  18 namespace mp4 {
  19
  20 // This class parses the AAC information from decoder specific information
  21 // embedded in the esds box in an ISO BMFF file.
  22 // Please refer to ISO 14496 Part 3 Table 1.13 - Syntax of AudioSpecificConfig
  23 // for more details.
  24 class MEDIA_EXPORT AAC {
  25  public:
  26   AAC();
  27   ~AAC();
  28
  29   // Parse the AAC config from the raw binary data embedded in esds box.
  30   // The function will parse the data and get the ElementaryStreamDescriptor,
  31   // then it will parse the ElementaryStreamDescriptor to get audio stream
  32   // configurations.
  33   bool Parse(const std::vector<uint8>& data);
  34
  35   // Gets the output sample rate for the AAC stream.
  36   // |sbr_in_mimetype| should be set to true if the SBR mode is
  37   // signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
  38   // Returns the samples_per_second value that should used in an
  39   // AudioDecoderConfig.
  40   int GetOutputSamplesPerSecond(bool sbr_in_mimetype) const;
  41
  42   // Gets the channel layout for the AAC stream.
  43   // |sbr_in_mimetype| should be set to true if the SBR mode is
  44   // signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
  45   // Returns the channel_layout value that should used in an
  46   // AudioDecoderConfig.
  47   ChannelLayout GetChannelLayout(bool sbr_in_mimetype) const;
  48
  49   // This function converts a raw AAC frame into an AAC frame with an ADTS
  50   // header. On success, the function returns true and stores the converted data
  51   // in the buffer. The function returns false on failure and leaves the buffer
  52   // unchanged.
  53   bool ConvertEsdsToADTS(std::vector<uint8>* buffer) const;
  54
  55   // Size in bytes of the ADTS header added by ConvertEsdsToADTS().
  56   static const size_t kADTSHeaderSize = 7;
  57
  58  private:
  59   bool SkipDecoderGASpecificConfig(BitReader* bit_reader) const;
  60   bool SkipErrorSpecificConfig() const;
  61   bool SkipGASpecificConfig(BitReader* bit_reader) const;
  62
  63   // The following variables store the AAC specific configuration information
  64   // that are used to generate the ADTS header.
  65   uint8 profile_;
  66   uint8 frequency_index_;
  67   uint8 channel_config_;
  68
  69   // The following variables store audio configuration information that
  70   // can be used by Chromium. They are based on the AAC specific
  71   // configuration but can be overridden by extensions in elementary
  72   // stream descriptor.
  73   int frequency_;
  74   int extension_frequency_;
  75   ChannelLayout channel_layout_;
  76 };
  77
  78 }  // namespace mp4
  79
  80 }  // namespace media
  81
  82 #endif  // MEDIA_MP4_AAC_H_