text: /*
   *  Copyright (c) 2014 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/splitting_filter.h"
  
  #include <array>
  
  #include "api/array_view.h"
  #include "common_audio/channel_buffer.h"
  #include "common_audio/signal_processing/include/signal_processing_library.h"
  #include "rtc_base/checks.h"
  
  namespace webrtc {
  namespace {
  
  constexpr size_t kSamplesPerBand = 160;
  constexpr size_t kTwoBandFilterSamplesPerFrame = 320;
  
  }  // namespace
  
  SplittingFilter::SplittingFilter(size_t num_channels,
                                   size_t num_bands,
                                   size_t num_frames)
      : num_bands_(num_bands),
        two_bands_states_(num_bands_ == 2 ? num_channels : 0),
        three_band_filter_banks_(num_bands_ == 3 ? num_channels : 0) {
    RTC_CHECK(num_bands_ == 2 || num_bands_ == 3);
  }
  
  SplittingFilter::~SplittingFilter() = default;
  
  void SplittingFilter::Analysis(const ChannelBuffer<float>* data,
                                 ChannelBuffer<float>* bands) {
    RTC_DCHECK_EQ(num_bands_, bands->num_bands());
    RTC_DCHECK_EQ(data->num_channels(), bands->num_channels());
    RTC_DCHECK_EQ(data->num_frames(),
                  bands->num_frames_per_band() * bands->num_bands());
    if (bands->num_bands() == 2) {
      TwoBandsAnalysis(data, bands);
    } else if (bands->num_bands() == 3) {
      ThreeBandsAnalysis(data, bands);
    }
  }
  
  void SplittingFilter::Synthesis(const ChannelBuffer<float>* bands,
                                  ChannelBuffer<float>* data) {
    RTC_DCHECK_EQ(num_bands_, bands->num_bands());
    RTC_DCHECK_EQ(data->num_channels(), bands->num_channels());
    RTC_DCHECK_EQ(data->num_frames(),
                  bands->num_frames_per_band() * bands->num_bands());
    if (bands->num_bands() == 2) {
      TwoBandsSynthesis(bands, data);
    } else if (bands->num_bands() == 3) {
      ThreeBandsSynthesis(bands, data);
    }
  }
  
  void SplittingFilter::TwoBandsAnalysis(const ChannelBuffer<float>* data,
                                         ChannelBuffer<float>* bands) {
    RTC_DCHECK_EQ(two_bands_states_.size(), data->num_channels());
    RTC_DCHECK_EQ(data->num_frames(), kTwoBandFilterSamplesPerFrame);
  
    for (size_t i = 0; i < two_bands_states_.size(); ++i) {
      std::array<std::array<int16_t, kSamplesPerBand>, 2> bands16;
      std::array<int16_t, kTwoBandFilterSamplesPerFrame> full_band16;
      FloatS16ToS16(data->channels(0)[i], full_band16.size(), full_band16.data());
      WebRtcSpl_AnalysisQMF(full_band16.data(), data->num_frames(),
                            bands16[0].data(), bands16[1].data(),
                            two_bands_states_[i].analysis_state1,
                            two_bands_states_[i].analysis_state2);
      S16ToFloatS16(bands16[0].data(), bands16[0].size(), bands->channels(0)[i]);
      S16ToFloatS16(bands16[1].data(), bands16[1].size(), bands->channels(1)[i]);
    }
  }
  
  void SplittingFilter::TwoBandsSynthesis(const ChannelBuffer<float>* bands,
                                          ChannelBuffer<float>* data) {
    RTC_DCHECK_LE(data->num_channels(), two_bands_states_.size());
    RTC_DCHECK_EQ(data->num_frames(), kTwoBandFilterSamplesPerFrame);
    for (size_t i = 0; i < data->num_channels(); ++i) {
      std::array<std::array<int16_t, kSamplesPerBand>, 2> bands16;
      std::array<int16_t, kTwoBandFilterSamplesPerFrame> full_band16;
      FloatS16ToS16(bands->channels(0)[i], bands16[0].size(), bands16[0].data());
      FloatS16ToS16(bands->channels(1)[i], bands16[1].size(), bands16[1].data());
      WebRtcSpl_SynthesisQMF(bands16[0].data(), bands16[1].data(),
                             bands->num_frames_per_band(), full_band16.data(),
                             two_bands_states_[i].synthesis_state1,
                             two_bands_states_[i].synthesis_state2);
      S16ToFloatS16(full_band16.data(), full_band16.size(), data->channels(0)[i]);
    }
  }
  
  void SplittingFilter::ThreeBandsAnalysis(const ChannelBuffer<float>* data,
                                           ChannelBuffer<float>* bands) {
    RTC_DCHECK_EQ(three_band_filter_banks_.size(), data->num_channels());
    RTC_DCHECK_LE(data->num_channels(), three_band_filter_banks_.size());
    RTC_DCHECK_LE(data->num_channels(), bands->num_channels());
    RTC_DCHECK_EQ(data->num_frames(), ThreeBandFilterBank::kFullBandSize);
    RTC_DCHECK_EQ(bands->num_frames(), ThreeBandFilterBank::kFullBandSize);
    RTC_DCHECK_EQ(bands->num_bands(), ThreeBandFilterBank::kNumBands);
    RTC_DCHECK_EQ(bands->num_frames_per_band(),
                  ThreeBandFilterBank::kSplitBandSize);
  
    for (size_t i = 0; i < three_band_filter_banks_.size(); ++i) {
      three_band_filter_banks_[i].Analysis(
          rtc::ArrayView<const float, ThreeBandFilterBank::kFullBandSize>(
              data->channels_view()[i].data(),
              ThreeBandFilterBank::kFullBandSize),
          rtc::ArrayView<const rtc::ArrayView<float>,
                         ThreeBandFilterBank::kNumBands>(
              bands->bands_view(i).data(), ThreeBandFilterBank::kNumBands));
    }
  }
  
  void SplittingFilter::ThreeBandsSynthesis(const ChannelBuffer<float>* bands,
                                            ChannelBuffer<float>* data) {
    RTC_DCHECK_LE(data->num_channels(), three_band_filter_banks_.size());
    RTC_DCHECK_LE(data->num_channels(), bands->num_channels());
    RTC_DCHECK_LE(data->num_channels(), three_band_filter_banks_.size());
    RTC_DCHECK_EQ(data->num_frames(), ThreeBandFilterBank::kFullBandSize);
    RTC_DCHECK_EQ(bands->num_frames(), ThreeBandFilterBank::kFullBandSize);
    RTC_DCHECK_EQ(bands->num_bands(), ThreeBandFilterBank::kNumBands);
    RTC_DCHECK_EQ(bands->num_frames_per_band(),
                  ThreeBandFilterBank::kSplitBandSize);
  
    for (size_t i = 0; i < data->num_channels(); ++i) {
      three_band_filter_banks_[i].Synthesis(
          rtc::ArrayView<const rtc::ArrayView<float>,
                         ThreeBandFilterBank::kNumBands>(
              bands->bands_view(i).data(), ThreeBandFilterBank::kNumBands),
          rtc::ArrayView<float, ThreeBandFilterBank::kFullBandSize>(
              data->channels_view()[i].data(),
              ThreeBandFilterBank::kFullBandSize));
    }
  }
  
  }  // namespace webrtc
  