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      1 // Copyright 2014 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_FORMATS_MP4_AAC_H_
      6 #define MEDIA_FORMATS_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 #include "media/base/media_log.h"
     14 
     15 namespace media {
     16 
     17 class BitReader;
     18 
     19 namespace mp4 {
     20 
     21 // This class parses the AAC information from decoder specific information
     22 // embedded in the esds box in an ISO BMFF file.
     23 // Please refer to ISO 14496 Part 3 Table 1.13 - Syntax of AudioSpecificConfig
     24 // for more details.
     25 class MEDIA_EXPORT AAC {
     26  public:
     27   AAC();
     28   ~AAC();
     29 
     30   // Parse the AAC config from the raw binary data embedded in esds box.
     31   // The function will parse the data and get the ElementaryStreamDescriptor,
     32   // then it will parse the ElementaryStreamDescriptor to get audio stream
     33   // configurations.
     34   bool Parse(const std::vector<uint8>& data, const LogCB& log_cb);
     35 
     36   // Gets the output sample rate for the AAC stream.
     37   // |sbr_in_mimetype| should be set to true if the SBR mode is
     38   // signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
     39   // Returns the samples_per_second value that should used in an
     40   // AudioDecoderConfig.
     41   int GetOutputSamplesPerSecond(bool sbr_in_mimetype) const;
     42 
     43   // Gets the channel layout for the AAC stream.
     44   // |sbr_in_mimetype| should be set to true if the SBR mode is
     45   // signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
     46   // Returns the channel_layout value that should used in an
     47   // AudioDecoderConfig.
     48   ChannelLayout GetChannelLayout(bool sbr_in_mimetype) const;
     49 
     50   // This function converts a raw AAC frame into an AAC frame with an ADTS
     51   // header. On success, the function returns true and stores the converted data
     52   // in the buffer. The function returns false on failure and leaves the buffer
     53   // unchanged.
     54   bool ConvertEsdsToADTS(std::vector<uint8>* buffer) const;
     55 
     56 #if defined(OS_ANDROID)
     57   // Returns the codec specific data needed by android MediaCodec.
     58   std::vector<uint8> codec_specific_data() const {
     59     return codec_specific_data_;
     60   }
     61 #endif
     62 
     63  private:
     64   bool SkipDecoderGASpecificConfig(BitReader* bit_reader) const;
     65   bool SkipErrorSpecificConfig() const;
     66   bool SkipGASpecificConfig(BitReader* bit_reader) const;
     67 
     68   // The following variables store the AAC specific configuration information
     69   // that are used to generate the ADTS header.
     70   uint8 profile_;
     71   uint8 frequency_index_;
     72   uint8 channel_config_;
     73 
     74 #if defined(OS_ANDROID)
     75   // The codec specific data needed by the android MediaCodec.
     76   std::vector<uint8> codec_specific_data_;
     77 #endif
     78 
     79   // The following variables store audio configuration information that
     80   // can be used by Chromium. They are based on the AAC specific
     81   // configuration but can be overridden by extensions in elementary
     82   // stream descriptor.
     83   int frequency_;
     84   int extension_frequency_;
     85   ChannelLayout channel_layout_;
     86 };
     87 
     88 }  // namespace mp4
     89 
     90 }  // namespace media
     91 
     92 #endif  // MEDIA_FORMATS_MP4_AAC_H_
     93