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/*
* Copyright (c) 2012 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/high_pass_filter.h"
#include <array>
#include <cstddef>
#include <vector>
#include "api/array_view.h"
#include "modules/audio_processing/audio_buffer.h"
#include "modules/audio_processing/utility/cascaded_biquad_filter.h"
#include "rtc_base/checks.h"
namespace webrtc {
namespace {
// [B,A] = butter(2,100/8000,'high')
constexpr std::array<CascadedBiQuadFilter::BiQuadCoefficients, 1>
kHighPassFilterCoefficients16kHz = {{
{{0.972613898f, -1.945227797f, 0.972613898f},
{-1.944477658f, 0.945977936f}},
}};
// [B,A] = butter(2,100/16000,'high')
constexpr std::array<CascadedBiQuadFilter::BiQuadCoefficients, 1>
kHighPassFilterCoefficients32kHz = {{
{{0.986211925f, -1.972423849f, 0.986211925f},
{-1.972233729f, 0.972613969f}},
}};
// [B,A] = butter(2,100/24000,'high')
constexpr std::array<CascadedBiQuadFilter::BiQuadCoefficients, 1>
kHighPassFilterCoefficients48kHz = {{
{{0.990786698f, -1.981573396f, 0.990786698f},
{-1.981488509f, 0.981658283f}},
}};
ArrayView<const CascadedBiQuadFilter::BiQuadCoefficients> ChooseCoefficients(
int sample_rate_hz) {
switch (sample_rate_hz) {
case 16000:
return ArrayView<const CascadedBiQuadFilter::BiQuadCoefficients>(
kHighPassFilterCoefficients16kHz);
case 32000:
return ArrayView<const CascadedBiQuadFilter::BiQuadCoefficients>(
kHighPassFilterCoefficients32kHz);
case 48000:
return ArrayView<const CascadedBiQuadFilter::BiQuadCoefficients>(
kHighPassFilterCoefficients48kHz);
default:
RTC_DCHECK_NOTREACHED();
}
RTC_DCHECK_NOTREACHED();
return ArrayView<const CascadedBiQuadFilter::BiQuadCoefficients>(
kHighPassFilterCoefficients16kHz);
}
} // namespace
HighPassFilter::HighPassFilter(int sample_rate_hz, size_t num_channels)
: sample_rate_hz_(sample_rate_hz) {
filters_.resize(num_channels);
auto coefficients = ChooseCoefficients(sample_rate_hz_);
for (size_t k = 0; k < filters_.size(); ++k) {
filters_[k].reset(new CascadedBiQuadFilter(coefficients));
}
}
HighPassFilter::~HighPassFilter() = default;
void HighPassFilter::Process(AudioBuffer* audio, bool use_split_band_data) {
RTC_DCHECK(audio);
RTC_DCHECK_EQ(filters_.size(), audio->num_channels());
if (use_split_band_data) {
for (size_t k = 0; k < audio->num_channels(); ++k) {
ArrayView<float> channel_data = ArrayView<float>(
audio->split_bands(k)[0], audio->num_frames_per_band());
filters_[k]->Process(channel_data);
}
} else {
for (size_t k = 0; k < audio->num_channels(); ++k) {
ArrayView<float> channel_data =
ArrayView<float>(&audio->channels()[k][0], audio->num_frames());
filters_[k]->Process(channel_data);
}
}
}
void HighPassFilter::Process(std::vector<std::vector<float>>* audio) {
RTC_DCHECK_EQ(filters_.size(), audio->size());
for (size_t k = 0; k < audio->size(); ++k) {
filters_[k]->Process((*audio)[k]);
}
}
void HighPassFilter::Reset() {
for (size_t k = 0; k < filters_.size(); ++k) {
filters_[k]->Reset();
}
}
void HighPassFilter::Reset(size_t num_channels) {
const size_t old_num_channels = filters_.size();
filters_.resize(num_channels);
if (filters_.size() < old_num_channels) {
Reset();
} else {
for (size_t k = 0; k < old_num_channels; ++k) {
filters_[k]->Reset();
}
const auto& coefficients = ChooseCoefficients(sample_rate_hz_);
for (size_t k = old_num_channels; k < filters_.size(); ++k) {
filters_[k].reset(new CascadedBiQuadFilter(coefficients));
}
}
}
} // namespace webrtc