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. codec_specific_data()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