1 /*
2  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef MODULES_AUDIO_PROCESSING_SPLITTING_FILTER_H_
12 #define MODULES_AUDIO_PROCESSING_SPLITTING_FILTER_H_
13 
14 #include <cstring>
15 #include <memory>
16 #include <vector>
17 
18 #include "modules/audio_processing/three_band_filter_bank.h"
19 
20 namespace webrtc {
21 
22 class IFChannelBuffer;
23 
24 struct TwoBandsStates {
TwoBandsStatesTwoBandsStates25   TwoBandsStates() {
26     memset(analysis_state1, 0, sizeof(analysis_state1));
27     memset(analysis_state2, 0, sizeof(analysis_state2));
28     memset(synthesis_state1, 0, sizeof(synthesis_state1));
29     memset(synthesis_state2, 0, sizeof(synthesis_state2));
30   }
31 
32   static const int kStateSize = 6;
33   int analysis_state1[kStateSize];
34   int analysis_state2[kStateSize];
35   int synthesis_state1[kStateSize];
36   int synthesis_state2[kStateSize];
37 };
38 
39 // Splitting filter which is able to split into and merge from 2 or 3 frequency
40 // bands. The number of channels needs to be provided at construction time.
41 //
42 // For each block, Analysis() is called to split into bands and then Synthesis()
43 // to merge these bands again. The input and output signals are contained in
44 // IFChannelBuffers and for the different bands an array of IFChannelBuffers is
45 // used.
46 class SplittingFilter {
47  public:
48   SplittingFilter(size_t num_channels, size_t num_bands, size_t num_frames);
49   ~SplittingFilter();
50 
51   void Analysis(const IFChannelBuffer* data, IFChannelBuffer* bands);
52   void Synthesis(const IFChannelBuffer* bands, IFChannelBuffer* data);
53 
54  private:
55   // Two-band analysis and synthesis work for 640 samples or less.
56   void TwoBandsAnalysis(const IFChannelBuffer* data, IFChannelBuffer* bands);
57   void TwoBandsSynthesis(const IFChannelBuffer* bands, IFChannelBuffer* data);
58   void ThreeBandsAnalysis(const IFChannelBuffer* data, IFChannelBuffer* bands);
59   void ThreeBandsSynthesis(const IFChannelBuffer* bands, IFChannelBuffer* data);
60   void InitBuffers();
61 
62   const size_t num_bands_;
63   std::vector<TwoBandsStates> two_bands_states_;
64   std::vector<std::unique_ptr<ThreeBandFilterBank>> three_band_filter_banks_;
65 };
66 
67 }  // namespace webrtc
68 
69 #endif  // MODULES_AUDIO_PROCESSING_SPLITTING_FILTER_H_
70