Home | History | Annotate | Download | only in mp4 
      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 #if defined(OS_ANDROID)
     56   // Returns the codec specific data needed by android MediaCodec.
     57   std::vector<uint8> codec_specific_data() const {
     58     return codec_specific_data_;
     59   }
     60 #endif
     61 
     62   // Size in bytes of the ADTS header added by ConvertEsdsToADTS().
     63   static const size_t kADTSHeaderSize = 7;
     64 
     65  private:
     66   bool SkipDecoderGASpecificConfig(BitReader* bit_reader) const;
     67   bool SkipErrorSpecificConfig() const;
     68   bool SkipGASpecificConfig(BitReader* bit_reader) const;
     69 
     70   // The following variables store the AAC specific configuration information
     71   // that are used to generate the ADTS header.
     72   uint8 profile_;
     73   uint8 frequency_index_;
     74   uint8 channel_config_;
     75 
     76 #if defined(OS_ANDROID)
     77   // The codec specific data needed by the android MediaCodec.
     78   std::vector<uint8> codec_specific_data_;
     79 #endif
     80 
     81   // The following variables store audio configuration information that
     82   // can be used by Chromium. They are based on the AAC specific
     83   // configuration but can be overridden by extensions in elementary
     84   // stream descriptor.
     85   int frequency_;
     86   int extension_frequency_;
     87   ChannelLayout channel_layout_;
     88 };
     89 
     90 }  // namespace mp4
     91 
     92 }  // namespace media
     93 
     94 #endif  // MEDIA_MP4_AAC_H_
     95