| 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_AMBISONICS_AMBISONIC_BINAURAL_DECODER_H_ |
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| 18 | #define RESONANCE_AUDIO_AMBISONICS_AMBISONIC_BINAURAL_DECODER_H_ |
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| 19 | |
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| 20 | #include <vector> |
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| 21 | |
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| 22 | #include "base/audio_buffer.h" |
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| 23 | #include "dsp/fft_manager.h" |
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| 24 | #include "dsp/partitioned_fft_filter.h" |
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| 25 | |
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| 26 | namespace vraudio { |
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| 27 | |
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| 28 | // Decodes an Ambisonic sound field, of an arbitrary order, to binaural stereo, |
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| 29 | // by performing convolution in the spherical harmonics domain. The order (hence |
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| 30 | // the number of channels) of the input must match the order (hence the number |
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| 31 | // of channels) of the spherical harmonic-encoded Head Related Impulse Responses |
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| 32 | // (HRIRs). Assumes that HRIRs are symmetric with respect to the sagittal plane. |
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| 33 | class AmbisonicBinauralDecoder { |
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| 34 | public: |
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| 35 | // Constructs an |AmbisonicBinauralDecoder| from an |AudioBuffer| containing |
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| 36 | // spherical harmonic representation of HRIRs. The order of spherical |
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| 37 | // harmonic-encoded HRIRs (hence the number of channels) must match the order |
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| 38 | // of the Ambisonic sound field input. |
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| 39 | // |
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| 40 | // @param sh_hrirs |AudioBuffer| containing time-domain spherical harmonic |
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| 41 | // encoded symmetric HRIRs. |
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| 42 | // @param frames_per_buffer Number of frames in each input/output buffer. |
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| 43 | // @param fft_manager Pointer to a manager to perform FFT transformations. |
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| 44 | AmbisonicBinauralDecoder(const AudioBuffer& sh_hrirs, |
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| 45 | size_t frames_per_buffer, FftManager* fft_manager); |
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| 46 | |
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| 47 | // Processes an Ambisonic sound field input and outputs a binaurally decoded |
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| 48 | // stereo buffer. |
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| 49 | // |
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| 50 | // @param input Input buffer to be processed. |
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| 51 | // @param output Pointer to a stereo output buffer. |
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| 52 | void Process(const AudioBuffer& input, AudioBuffer* output); |
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| 53 | |
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| 54 | private: |
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| 55 | // Manager for all FFT related functionality (not owned). |
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| 56 | FftManager* const fft_manager_; |
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| 57 | |
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| 58 | // Spherical Harmonic HRIR filter kernels. |
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| 59 | std::vector<std::unique_ptr<PartitionedFftFilter>> sh_hrir_filters_; |
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| 60 | |
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| 61 | // Frequency domain representation of the input signal. |
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| 62 | PartitionedFftFilter::FreqDomainBuffer freq_input_; |
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| 63 | |
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| 64 | // Temporary audio buffer to store the convolution output for asymmetric or |
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| 65 | // symmetric spherical harmonic HRIR. |
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| 66 | AudioBuffer filtered_input_; |
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| 67 | }; |
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| 68 | |
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| 69 | } // namespace vraudio |
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| 70 | |
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| 71 | #endif // RESONANCE_AUDIO_AMBISONICS_AMBISONIC_BINAURAL_DECODER_H_ |
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| 72 | |
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