1 | /* |
2 | Copyright 2018 Google Inc. All Rights Reserved. |
3 | |
4 | Licensed under the Apache License, Version 2.0 (the "License"); |
5 | you may not use this file except in compliance with the License. |
6 | You may obtain a copy of the License at |
7 | |
8 | http://www.apache.org/licenses/LICENSE-2.0 |
9 | |
10 | Unless required by applicable law or agreed to in writing, software |
11 | distributed under the License is distributed on an "AS-IS" BASIS, |
12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
13 | See the License for the specific language governing permissions and |
14 | limitations under the License. |
15 | */ |
16 | |
17 | #ifndef RESONANCE_AUDIO_DSP_FFT_MANAGER_H_ |
18 | #define RESONANCE_AUDIO_DSP_FFT_MANAGER_H_ |
19 | |
20 | #include "pffft.h" |
21 | #include "base/audio_buffer.h" |
22 | |
23 | namespace vraudio { |
24 | |
25 | // This class wraps the pffft library and enables reall FFT transformations to |
26 | // be performed on aligned float buffers of data. The class also manages all |
27 | // necessary data buffers and zero padding. This class is not thread safe. |
28 | class FftManager { |
29 | public: |
30 | // Minimum required FFT size. |
31 | static const size_t kMinFftSize; |
32 | |
33 | // Constructs a FftManager insatnce. One instance of this class can be shared. |
34 | // This class is not thread safe. |
35 | // |
36 | // @param frames_per_buffer System's number of frames per buffer. |
37 | explicit FftManager(size_t frames_per_buffer); |
38 | |
39 | // Destroys a FftManager instance freeing associated aligned memory. |
40 | ~FftManager(); |
41 | |
42 | // Transforms a single channel of time domain input data into a frequency |
43 | // domain representation. |
44 | // |
45 | // @param time_channel Time domain input. If the length is less than |
46 | // |fft_size_|, the input is zeropadded. The max length is |fft_size_|. |
47 | // @param freq_channel Frequency domain output, |fft_size| samples long. |
48 | void FreqFromTimeDomain(const AudioBuffer::Channel& time_channel, |
49 | AudioBuffer::Channel* freq_channel); |
50 | |
51 | // Transforms a single channel of frequency domain input data into a time |
52 | // domain representation. Note: The input must be in pffft format see: |
53 | // goo.gl/LYbgX7. This method can output to a buffer of either |
54 | // |frames_per_buffer_| or |fft_size_| in length. This feature ensures an |
55 | // additional copy is not needed where this method is to be used with an |
56 | // overlap add. |
57 | // |
58 | // @param freq_channel Frequency domain input, |fft_size| samples long. |
59 | // @param time_channel Time domain output, |frames_per_buffer_| samples long |
60 | // OR |fft_size_| samples long. |
61 | void TimeFromFreqDomain(const AudioBuffer::Channel& freq_channel, |
62 | AudioBuffer::Channel* time_channel); |
63 | |
64 | // Applies a 1/|fft_size_| scaling to time domain output. NOTE this need not |
65 | // be applied where a convolution is taking place as the scaling will be |
66 | // included therein. |
67 | // |
68 | // @param time_channel Time domain data to be scaled. |
69 | void ApplyReverseFftScaling(AudioBuffer::Channel* time_channel); |
70 | |
71 | // Transforms a pffft frequency domain format buffer into canonical format |
72 | // with alternating real and imaginary values with increasing frequency. The |
73 | // first two entries of |output| are the real part of the DC and Nyquist |
74 | // frequencies (imaginary part is zero). The alternating real and imaginary |
75 | // parts start from the third entry in |output|. For more info on the pffft |
76 | // format see: goo.gl/LYbgX7 |
77 | // |
78 | // @param input Frequency domain input channel, |fft_size| samples long. |
79 | // @param output Frequency domain output channel,|fft_size| samples long. |
80 | void GetCanonicalFormatFreqBuffer(const AudioBuffer::Channel& input, |
81 | AudioBuffer::Channel* output); |
82 | |
83 | // Transforms a canonical frequency domain format buffer into pffft format. |
84 | // For more info on the pffft format see: goo.gl/LYbgX7 |
85 | // |
86 | // @param input Frequency domain input channel, |fft_size| samples long. |
87 | // @param output Frequency domain output channel, |fft_size| samples long. |
88 | void GetPffftFormatFreqBuffer(const AudioBuffer::Channel& input, |
89 | AudioBuffer::Channel* output); |
90 | |
91 | // Genarates a buffer containing the single sided magnitude spectrum of a |
92 | // frequency domain buffer. The input must be in Canonical format. The output |
93 | // will have DC frequency as it's first entry and the Nyquist as it's last. |
94 | // |
95 | // @param freq_channel Canonical format frequency domain buffer, |
96 | // |fft_size_| samples long. |
97 | // @param magnitude_channel Magnitude of the |freq_channel|. |
98 | // |frames_per_buffer_| + 1 samples long. |
99 | void MagnitudeFromCanonicalFreqBuffer( |
100 | const AudioBuffer::Channel& freq_channel, |
101 | AudioBuffer::Channel* magnitude_channel); |
102 | |
103 | // Combines single sided magnitude and phase spectra into a canonical format |
104 | // frequency domain buffer. The inputs must have DC frequency as their first |
105 | // entry and the Nyquist as their last. |
106 | // |
107 | // @param magnitude_channel Magnitude of the |frequency_buffer|. |
108 | // |frames_per_buffer_| + 1 samples long. |
109 | // @param phase_channel Phase of the |frequency_buffer|. |
110 | // |frames_per_buffer_| + 1 samples long. |
111 | // @param canonical_freq_channel Canonical format frequency domain buffer, |
112 | // |fft_size_| samples long. |
113 | void CanonicalFreqBufferFromMagnitudeAndPhase( |
114 | const AudioBuffer::Channel& magnitude_channel, |
115 | const AudioBuffer::Channel& phase_channel, |
116 | AudioBuffer::Channel* canonical_freq_channel); |
117 | |
118 | // Combines single sided magnitude spectrum and the cosine and sine of a phase |
119 | // spectrum into a canonical format frequency domain buffer. The inputs must |
120 | // have DC frequency as their first entry and the Nyquist as their last. |
121 | // The phase spectra channels can be offset by |phase_offset|. This feature |
122 | // is specifically for use as an optimization in the |SpectralReverb|. |
123 | // |
124 | // @param phase_offset An offset into the channels of the phase buffer. |
125 | // @param magnitude_channel Magnitude of the |frequency_buffer|. |
126 | // |frames_per_buffer_| + 1 samples long. |
127 | // @param sin_phase_channel Sine of the phase of the |frequency_buffer|. |
128 | // |frames_per_buffer_| + 1 samples long. |
129 | // @param cos_phase_channel Cosine of the phase of the |frequency_buffer|. |
130 | // |frames_per_buffer_| + 1 samples long. |
131 | // @param canonical_freq_channel Canonical format frequency domain buffer, |
132 | // |fft_size_| samples long. |
133 | void CanonicalFreqBufferFromMagnitudeAndSinCosPhase( |
134 | size_t phase_offset, const AudioBuffer::Channel& magnitude_channel, |
135 | const AudioBuffer::Channel& sin_phase_channel, |
136 | const AudioBuffer::Channel& cos_phase_channel, |
137 | AudioBuffer::Channel* canonical_freq_channel); |
138 | |
139 | // Performs a pointwise complex multiplication of two frequency domain buffers |
140 | // and applies tha inverse scaling factor of 1/|fft_size_|. This operation is |
141 | // equivalent to a time domain circular convolution. |
142 | // |
143 | // @param input_a Frequency domain input channel, |fft_size| samples long. |
144 | // @param input_b Frequency domain input channel, |fft_size| samples long. |
145 | // @param scaled_output Frequency domain output channel, |fft_size| samples |
146 | // long. |
147 | void FreqDomainConvolution(const AudioBuffer::Channel& input_a, |
148 | const AudioBuffer::Channel& input_b, |
149 | AudioBuffer::Channel* scaled_output); |
150 | |
151 | // Returns the number of points in the FFT. |
152 | size_t GetFftSize() const { return fft_size_; } |
153 | |
154 | private: |
155 | // FFT size in samples. |
156 | const size_t fft_size_; |
157 | |
158 | // Number of frames in each buffer of input data. |
159 | const size_t frames_per_buffer_; |
160 | |
161 | // Inverse scale to be applied to buffers transformed from frequency to time |
162 | // domain. |
163 | const float inverse_fft_scale_; |
164 | |
165 | // Temporary time domain buffer to store zeropadded input. |
166 | AudioBuffer temp_zeropad_buffer_; |
167 | |
168 | // Temporary freq domain buffer to store. |
169 | AudioBuffer temp_freq_buffer_; |
170 | |
171 | // pffft states. |
172 | PFFFT_Setup* fft_; |
173 | |
174 | // Workspace for pffft. This pointer should be set to null for |fft_size_| |
175 | // less than 2^14. In which case the stack is used. This is the recommendation |
176 | // by the author of the pffft library. |
177 | float* pffft_workspace_ = nullptr; |
178 | }; |
179 | |
180 | } // namespace vraudio |
181 | |
182 | #endif // RESONANCE_AUDIO_DSP_FFT_MANAGER_H_ |
183 | |