92 lines
2.8 KiB
C++
92 lines
2.8 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef MEDIA_MP4_AAC_H_
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#define MEDIA_MP4_AAC_H_
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#include <vector>
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#include "base/basictypes.h"
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namespace media {
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class BitReader;
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namespace mp4 {
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// This class parses the AAC information from decoder specific information
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// embedded in the esds box in an ISO BMFF file.
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// Please refer to ISO 14496 Part 3 Table 1.13 - Syntax of AudioSpecificConfig
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// for more details.
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// TODO(kqyang): the class name is not appropriate, it should be
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// AACAudioSpecificConfig instead.
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class AAC {
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public:
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AAC();
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~AAC();
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// Parse the AAC config from the raw binary data embedded in esds box.
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// The function will parse the data and get the ElementaryStreamDescriptor,
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// then it will parse the ElementaryStreamDescriptor to get audio stream
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// configurations.
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bool Parse(const std::vector<uint8>& data);
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// Gets the output sample rate for the AAC stream.
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// |sbr_in_mimetype| should be set to true if the SBR mode is
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// signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
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uint32 GetOutputSamplesPerSecond(bool sbr_in_mimetype) const;
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// Gets number of channels for the AAC stream.
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// |sbr_in_mimetype| should be set to true if the SBR mode is
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// signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
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uint8 GetNumChannels(bool sbr_in_mimetype) const;
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// This function converts a raw AAC frame into an AAC frame with an ADTS
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// header. On success, the function returns true and stores the converted data
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// in the buffer. The function returns false on failure and leaves the buffer
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// unchanged.
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bool ConvertToADTS(std::vector<uint8>* buffer) const;
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uint8 audio_object_type() const {
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return audio_object_type_;
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}
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uint32 frequency() const {
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return frequency_;
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}
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uint8 num_channels() const {
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return num_channels_;
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}
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// Size in bytes of the ADTS header added by ConvertEsdsToADTS().
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static const size_t kADTSHeaderSize = 7;
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private:
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bool SkipDecoderGASpecificConfig(BitReader* bit_reader) const;
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bool SkipErrorSpecificConfig() const;
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bool SkipGASpecificConfig(BitReader* bit_reader) const;
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// The following variables store the AAC specific configuration information
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// that are used to generate the ADTS header.
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uint8 audio_object_type_;
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uint8 frequency_index_;
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uint8 channel_config_;
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// Is Parametric Stereo on?
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bool ps_present_;
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// The following variables store audio configuration information.
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// They are based on the AAC specific configuration but can be overridden
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// by extensions in elementary stream descriptor.
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uint32 frequency_;
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uint32 extension_frequency_;
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uint8 num_channels_;
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};
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} // namespace mp4
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} // namespace media
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#endif // MEDIA_MP4_AAC_H_
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