1 /* 2 * Copyright (c) 2015 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 WEBRTC_COMMON_AUDIO_SPARSE_FIR_FILTER_H_ 12 #define WEBRTC_COMMON_AUDIO_SPARSE_FIR_FILTER_H_ 13 14 #include <cstring> 15 #include <vector> 16 17 #include "webrtc/base/constructormagic.h" 18 19 namespace webrtc { 20 21 // A Finite Impulse Response filter implementation which takes advantage of a 22 // sparse structure with uniformly distributed non-zero coefficients. 23 class SparseFIRFilter final { 24 public: 25 // |num_nonzero_coeffs| is the number of non-zero coefficients, 26 // |nonzero_coeffs|. They are assumed to be uniformly distributed every 27 // |sparsity| samples and with an initial |offset|. The rest of the filter 28 // coefficients will be assumed zeros. For example, with sparsity = 3, and 29 // offset = 1 the filter coefficients will be: 30 // B = [0 coeffs[0] 0 0 coeffs[1] 0 0 coeffs[2] ... ] 31 // All initial state values will be zeros. 32 SparseFIRFilter(const float* nonzero_coeffs, 33 size_t num_nonzero_coeffs, 34 size_t sparsity, 35 size_t offset); 36 37 // Filters the |in| data supplied. 38 // |out| must be previously allocated and it must be at least of |length|. 39 void Filter(const float* in, size_t length, float* out); 40 41 private: 42 const size_t sparsity_; 43 const size_t offset_; 44 const std::vector<float> nonzero_coeffs_; 45 std::vector<float> state_; 46 47 RTC_DISALLOW_COPY_AND_ASSIGN(SparseFIRFilter); 48 }; 49 50 } // namespace webrtc 51 52 #endif // WEBRTC_COMMON_AUDIO_SPARSE_FIR_FILTER_H_ 53
