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/*
* Copyright (c) 2016 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 "modules/audio_processing/agc2/biquad_filter.h"
#include "rtc_base/arraysize.h"
namespace webrtc {
BiQuadFilter::BiQuadFilter(const Config& config)
: config_(config), state_({}) {}
BiQuadFilter::~BiQuadFilter() = default;
void BiQuadFilter::SetConfig(const Config& config) {
config_ = config;
state_ = {};
}
void BiQuadFilter::Reset() {
state_ = {};
}
void BiQuadFilter::Process(rtc::ArrayView<const float> x,
rtc::ArrayView<float> y) {
RTC_DCHECK_EQ(x.size(), y.size());
const float config_a0 = config_.a[0];
const float config_a1 = config_.a[1];
const float config_b0 = config_.b[0];
const float config_b1 = config_.b[1];
const float config_b2 = config_.b[2];
float state_a0 = state_.a[0];
float state_a1 = state_.a[1];
float state_b0 = state_.b[0];
float state_b1 = state_.b[1];
for (size_t k = 0, x_size = x.size(); k < x_size; ++k) {
// Use a temporary variable for `x[k]` to allow in-place processing.
const float tmp = x[k];
float y_k = config_b0 * tmp + config_b1 * state_b0 + config_b2 * state_b1 -
config_a0 * state_a0 - config_a1 * state_a1;
state_b1 = state_b0;
state_b0 = tmp;
state_a1 = state_a0;
state_a0 = y_k;
y[k] = y_k;
}
state_.a[0] = state_a0;
state_.a[1] = state_a1;
state_.b[0] = state_b0;
state_.b[1] = state_b1;
}
} // namespace webrtc
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