Introduced the new parameter setting scheme for activating the high-pass filter in APM

webrtc/modules/audio_processing/high_pass_filter_impl.cc

-/*
- *  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 "webrtc/modules/audio_processing/high_pass_filter_impl.h"
-
-#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
-#include "webrtc/modules/audio_processing/audio_buffer.h"
-#include "webrtc/system_wrappers/include/critical_section_wrapper.h"
-
-namespace webrtc {
-namespace {
-const int16_t kFilterCoefficients8kHz[5] = {3798, -7596, 3798, 7807, -3733};
-const int16_t kFilterCoefficients[5] = {4012, -8024, 4012, 8002, -3913};
-}  // namespace
-
-class HighPassFilterImpl::BiquadFilter {
- public:
-  explicit BiquadFilter(int sample_rate_hz) :
-      ba_(sample_rate_hz == AudioProcessing::kSampleRate8kHz ?
-          kFilterCoefficients8kHz : kFilterCoefficients)
-  {
-    Reset();
-  }
-
-  void Reset() {
-    std::memset(x_, 0, sizeof(x_));
-    std::memset(y_, 0, sizeof(y_));
-  }
-
-  void Process(int16_t* data, size_t length) {
-    const int16_t* const ba = ba_;
-    int16_t* x = x_;
-    int16_t* y = y_;
-    int32_t tmp_int32 = 0;
-
-    for (size_t i = 0; i < length; i++) {
-      //  y[i] = b[0] * x[i] +  b[1] * x[i-1] +  b[2] * x[i-2]
-      //                     + -a[1] * y[i-1] + -a[2] * y[i-2];
-
-      tmp_int32 = y[1] * ba[3];      // -a[1] * y[i-1] (low part)
-      tmp_int32 += y[3] * ba[4];     // -a[2] * y[i-2] (low part)
-      tmp_int32 = (tmp_int32 >> 15);
-      tmp_int32 += y[0] * ba[3];     // -a[1] * y[i-1] (high part)
-      tmp_int32 += y[2] * ba[4];     // -a[2] * y[i-2] (high part)
-      tmp_int32 = (tmp_int32 << 1);
-
-      tmp_int32 += data[i] * ba[0];  // b[0] * x[0]
-      tmp_int32 += x[0] * ba[1];     // b[1] * x[i-1]
-      tmp_int32 += x[1] * ba[2];     // b[2] * x[i-2]
-
-      // Update state (input part).
-      x[1] = x[0];
-      x[0] = data[i];
-
-      // Update state (filtered part).
-      y[2] = y[0];
-      y[3] = y[1];
-      y[0] = static_cast<int16_t>(tmp_int32 >> 13);
-      y[1] = static_cast<int16_t>(
-          (tmp_int32 - (static_cast<int32_t>(y[0]) << 13)) << 2);
-
-      // Rounding in Q12, i.e. add 2^11.
-      tmp_int32 += 2048;
-
-      // Saturate (to 2^27) so that the HP filtered signal does not overflow.
-      tmp_int32 = WEBRTC_SPL_SAT(static_cast<int32_t>(134217727),
-                                 tmp_int32,
-                                 static_cast<int32_t>(-134217728));
-
-      // Convert back to Q0 and use rounding.
-      data[i] = static_cast<int16_t>(tmp_int32 >> 12);
-    }
-  }
-
- private:
-  const int16_t* const ba_ = nullptr;
-  int16_t x_[2];
-  int16_t y_[4];
-};
-
-HighPassFilterImpl::HighPassFilterImpl(rtc::CriticalSection* crit)
-    : crit_(crit) {
-  RTC_DCHECK(crit_);
-}
-
-HighPassFilterImpl::~HighPassFilterImpl() {}
-
-void HighPassFilterImpl::Initialize(size_t channels, int sample_rate_hz) {
-  std::vector<std::unique_ptr<BiquadFilter>> new_filters(channels);
-  for (size_t i = 0; i < channels; i++) {
-    new_filters[i].reset(new BiquadFilter(sample_rate_hz));
-  }
-  rtc::CritScope cs(crit_);
-  filters_.swap(new_filters);
-}
-
-void HighPassFilterImpl::ProcessCaptureAudio(AudioBuffer* audio) {
-  RTC_DCHECK(audio);
-  rtc::CritScope cs(crit_);
-  if (!enabled_) {
-    return;
-  }
-
-  RTC_DCHECK_GE(160u, audio->num_frames_per_band());
-  RTC_DCHECK_EQ(filters_.size(), audio->num_channels());
-  for (size_t i = 0; i < filters_.size(); i++) {
-    filters_[i]->Process(audio->split_bands(i)[kBand0To8kHz],
-                         audio->num_frames_per_band());
-  }
-}
-
-int HighPassFilterImpl::Enable(bool enable) {
-  rtc::CritScope cs(crit_);
-  if (!enabled_ && enable) {
-    for (auto& filter : filters_) {
-      filter->Reset();
-    }
-  }
-  enabled_ = enable;
-  return AudioProcessing::kNoError;
-}
-
-bool HighPassFilterImpl::is_enabled() const {
-  rtc::CritScope cs(crit_);
-  return enabled_;
-}
-}  // namespace webrtc