| 1 | /* |
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| 2 | Copyright 2018 Google Inc. All Rights Reserved. |
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| 3 | |
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| 4 | Licensed under the Apache License, Version 2.0 (the "License"); |
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| 5 | you may not use this file except in compliance with the License. |
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| 6 | You may obtain a copy of the License at |
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| 7 | |
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| 8 | http://www.apache.org/licenses/LICENSE-2.0 |
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| 9 | |
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| 10 | Unless required by applicable law or agreed to in writing, software |
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| 11 | distributed under the License is distributed on an "AS-IS" BASIS, |
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| 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 13 | See the License for the specific language governing permissions and |
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| 14 | limitations under the License. |
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| 15 | */ |
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| 16 | |
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| 17 | #ifndef RESONANCE_AUDIO_DSP_MIXER_H_ |
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| 18 | #define RESONANCE_AUDIO_DSP_MIXER_H_ |
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| 19 | |
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| 20 | #include <memory> |
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| 21 | |
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| 22 | #include "base/audio_buffer.h" |
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| 23 | |
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| 24 | namespace vraudio { |
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| 25 | |
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| 26 | // Accepts multiple input buffers and outputs a downmix to a single output |
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| 27 | // buffer. All input buffers must have the same number of frames per buffer, the |
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| 28 | // output will have the target number of channels regardless of the input number |
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| 29 | // of channels. |
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| 30 | class Mixer { |
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| 31 | public: |
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| 32 | // Constructor. |
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| 33 | // |
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| 34 | // @param target_num_channels Target number of channels in accumulator buffer. |
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| 35 | // @param frames_per_buffer Number of frames in accumulator buffer. |
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| 36 | Mixer(size_t target_num_channels, size_t frames_per_buffer); |
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| 37 | |
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| 38 | // Adds an input buffer to the mixer, updates the output buffer accordingly. |
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| 39 | // |
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| 40 | // @param input Input buffer to be added. |
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| 41 | void AddInput(const AudioBuffer& input); |
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| 42 | |
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| 43 | // Returns a pointer to the accumulator. |
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| 44 | // |
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| 45 | // @return Pointer to the processed (mixed) output buffer, or nullptr if no |
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| 46 | // input has been added to the accumulator. |
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| 47 | const AudioBuffer* GetOutput() const; |
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| 48 | |
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| 49 | // Resets the state of the accumulator. |
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| 50 | void Reset(); |
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| 51 | |
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| 52 | private: |
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| 53 | // Output buffer (accumulator). |
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| 54 | AudioBuffer output_; |
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| 55 | |
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| 56 | // Denotes whether the accumulator has processed any inputs or not. |
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| 57 | bool is_empty_; |
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| 58 | }; |
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| 59 | |
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| 60 | } // namespace vraudio |
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| 61 | |
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| 62 | #endif // RESONANCE_AUDIO_DSP_MIXER_H_ |
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| 63 | |
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