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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.
*/
#include "common_audio/sparse_fir_filter.h"
#include "rtc_base/checks.h"
namespace webrtc {
SparseFIRFilter::SparseFIRFilter(const float* nonzero_coeffs,
size_t num_nonzero_coeffs,
size_t sparsity,
size_t offset)
: sparsity_(sparsity),
offset_(offset),
nonzero_coeffs_(nonzero_coeffs, nonzero_coeffs + num_nonzero_coeffs),
state_(sparsity_ * (num_nonzero_coeffs - 1) + offset_, 0.f) {
RTC_CHECK_GE(num_nonzero_coeffs, 1);
RTC_CHECK_GE(sparsity, 1);
}
SparseFIRFilter::~SparseFIRFilter() = default;
void SparseFIRFilter::Filter(const float* in, size_t length, float* out) {
// Convolves the input signal |in| with the filter kernel |nonzero_coeffs_|
// taking into account the previous state.
for (size_t i = 0; i < length; ++i) {
out[i] = 0.f;
size_t j;
for (j = 0; i >= j * sparsity_ + offset_ && j < nonzero_coeffs_.size();
++j) {
out[i] += in[i - j * sparsity_ - offset_] * nonzero_coeffs_[j];
}
for (; j < nonzero_coeffs_.size(); ++j) {
out[i] += state_[i + (nonzero_coeffs_.size() - j - 1) * sparsity_] *
nonzero_coeffs_[j];
}
}
// Update current state.
if (!state_.empty()) {
if (length >= state_.size()) {
std::memcpy(&state_[0], &in[length - state_.size()],
state_.size() * sizeof(*in));
} else {
std::memmove(&state_[0], &state_[length],
(state_.size() - length) * sizeof(state_[0]));
std::memcpy(&state_[state_.size() - length], in, length * sizeof(*in));
}
}
}
} // namespace webrtc
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