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/*
* Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef WEBRTC_COMMON_AUDIO_SPARSE_FIR_FILTER_H_
#define WEBRTC_COMMON_AUDIO_SPARSE_FIR_FILTER_H_
#include <cstring>
#include <vector>
#include "webrtc/base/constructormagic.h"
namespace webrtc {
// A Finite Impulse Response filter implementation which takes advantage of a
// sparse structure with uniformly distributed non-zero coefficients.
class SparseFIRFilter final {
public:
// |num_nonzero_coeffs| is the number of non-zero coefficients,
// |nonzero_coeffs|. They are assumed to be uniformly distributed every
// |sparsity| samples and with an initial |offset|. The rest of the filter
// coefficients will be assumed zeros. For example, with sparsity = 3, and
// offset = 1 the filter coefficients will be:
// B = [0 coeffs[0] 0 0 coeffs[1] 0 0 coeffs[2] ... ]
// All initial state values will be zeros.
SparseFIRFilter(const float* nonzero_coeffs,
size_t num_nonzero_coeffs,
size_t sparsity,
size_t offset);
// Filters the |in| data supplied.
// |out| must be previously allocated and it must be at least of |length|.
void Filter(const float* in, size_t length, float* out);
private:
const size_t sparsity_;
const size_t offset_;
const std::vector<float> nonzero_coeffs_;
std::vector<float> state_;
RTC_DISALLOW_COPY_AND_ASSIGN(SparseFIRFilter);
};
} // namespace webrtc
#endif // WEBRTC_COMMON_AUDIO_SPARSE_FIR_FILTER_H_
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