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_MULTI_CHANNEL_IIR_H_ |
18 | #define RESONANCE_AUDIO_DSP_MULTI_CHANNEL_IIR_H_ |
19 | |
20 | #include <memory> |
21 | #include <vector> |
22 | |
23 | #include "base/audio_buffer.h" |
24 | |
25 | namespace vraudio { |
26 | |
27 | // Class that performs IIR filtering on interleaved data. This class can be used |
28 | // to implement any order of IIR filter on multichannel data where the number of |
29 | // channels is a multiple of the SIMD vector length. |
30 | class MultiChannelIir { |
31 | public: |
32 | // Returns a |MultiChannelIir| given valid parameters. |
33 | // |
34 | // @param num_channels Number of channels in each input buffer. The number of |
35 | // channels must be divisible by |SIMD_LENGTH|. |
36 | // @param frames_per_buffer Number of frames in each input buffer. |
37 | // @param numerators Numerator coefficients, one set per channel. |
38 | // @param denominators Denominator coefficients, should be equal in length to |
39 | // the |numerator| vector, one set per channel. |
40 | // @return A |MultiChannelIir| instance. |
41 | static std::unique_ptr<MultiChannelIir> Create( |
42 | size_t num_channels, size_t frames_per_buffer, |
43 | const std::vector<std::vector<float>>& numerators, |
44 | const std::vector<std::vector<float>>& denominators); |
45 | |
46 | // Processes an interleaved buffer of input data with the given IIR filter. |
47 | // |
48 | // @param interleaved_buffer A single channel of data containing input in |
49 | // interleaved format, this will contain output data in interleaved format |
50 | // on return. |
51 | void Process(AudioBuffer::Channel* interleaved_buffer); |
52 | |
53 | private: |
54 | // Constructs a |MultiChannelIir|. |
55 | // |
56 | // @param num_channels Number of channels in each input buffer. The number of |
57 | // channels must be divisible by |SIMD_LENGTH|. |
58 | // @param frames_per_buffer Number of frames in each input buffer. |
59 | // @param num_coefficients Number of coefficients in the numerator, which |
60 | // equals the number in the denominator. |
61 | MultiChannelIir(size_t num_channels, size_t frames_per_buffer, |
62 | size_t num_coefficients); |
63 | |
64 | // Number of channels in each input buffer. |
65 | const size_t num_channels_; |
66 | |
67 | // Number of frames in each input buffer. |
68 | const size_t frames_per_buffer_; |
69 | |
70 | // Number of coefficients in the numerator and denominator polynomials. |
71 | const size_t num_coefficients_; |
72 | |
73 | // Current front of the delay line which is circularly indexed. |
74 | size_t delay_line_front_; |
75 | |
76 | // Stores numerator coefficients in repeated fashion. |
77 | AudioBuffer numerator_; |
78 | |
79 | // Stores denominator coefficients in repeated fashion. |
80 | AudioBuffer denominator_; |
81 | |
82 | // Holds previous data computed from the numerator section. |
83 | AudioBuffer delay_line_; |
84 | }; |
85 | |
86 | } // namespace vraudio |
87 | |
88 | #endif // RESONANCE_AUDIO_DSP_MULTI_CHANNEL_IIR_H_ |
89 | |