text: // Copyright 2014 Emilie Gillet.
  //
  // Author: Emilie Gillet (emilie.o.gillet@gmail.com)
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  // 
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  // 
  // See http://creativecommons.org/licenses/MIT/ for more information.
  //
  // -----------------------------------------------------------------------------
  //
  // Filter bank.
  
  #include "warps/dsp/filter_bank.h"
  
  #include <algorithm>
  
  #include "warps/resources.h"
  
  namespace warps {
  
  using namespace std;
  using namespace stmlib;
  
  void FilterBank::Init(float sample_rate) {
    low_src_down_.Init();
    low_src_up_.Init();
    mid_src_down_.Init();
    mid_src_up_.Init();
    
    int32_t max_delay = 0;
    float* samples = &samples_[0];
    
    int32_t group = -1;
    int32_t decimation_factor = -1;
    for (int32_t i = 0; i < kNumBands; ++i) {
      const float* coefficients = filter_bank_table[i];
  
      Band& b = band_[i];
  
      b.decimation_factor = static_cast<int32_t>(coefficients[0]);
      
      if (b.decimation_factor != decimation_factor) {
        decimation_factor = b.decimation_factor;
        ++group;
      }
      
      b.group = group;
      b.sample_rate = sample_rate / static_cast<float>(b.decimation_factor);
      b.samples = samples;
      samples += kMaxFilterBankBlockSize / b.decimation_factor;
      
      b.delay = static_cast<int32_t>(coefficients[1]);
      b.delay *= b.decimation_factor;
      b.post_gain = coefficients[2];
  
      max_delay = max(max_delay, b.delay);
      for (int32_t pass = 0; pass < 2; ++pass) {
        b.svf[pass].Init();
        b.svf[pass].set_f_fq(
            coefficients[pass * 2 + 3],
            coefficients[pass * 2 + 4]);
      }
    }
    band_[kNumBands].group = band_[kNumBands - 1].group + 1;
    max_delay = min(max_delay, int32_t(256));
    float* delay_ptr = &delay_buffer_[0];
    for (int32_t i = 0; i < kNumBands; ++i) {
      Band& b = band_[i];
      int32_t compensation = max_delay - b.delay;
      if (b.group == 0) {
        compensation -= kLowFactor * \
            (low_src_down_.delay() + low_src_up_.delay());
        compensation -= mid_src_down_.delay();
        compensation -= mid_src_up_.delay();
      } else if (b.group == 1) {
        compensation -= mid_src_down_.delay();
        compensation -= mid_src_up_.delay();
      }
      compensation = max(compensation - b.decimation_factor / 2, int32_t(0));
      b.delay_line.Init(delay_ptr, compensation / b.decimation_factor);
      delay_ptr += b.delay_line.size();
    }
  }
  
  void FilterBank::Analyze(const float* in, size_t size) {
    mid_src_down_.Process(in, tmp_[0], size);
    low_src_down_.Process(tmp_[0], tmp_[1], size / kMidFactor);
    
    const float* sources[3] = { tmp_[1], tmp_[0], in };
    for (int32_t i = 0; i < kNumBands; ++i) {
      Band& b = band_[i];
      const size_t band_size = size;
      const float* input = sources[b.group];
      
      for (int32_t pass = 0; pass < 2; ++pass) {
        const float* source = pass == 0 ? input : b.samples;
        float* destination = b.samples;
        if (i == 0) {
          b.svf[pass].Process<FILTER_MODE_LOW_PASS>(
              source, destination, band_size);
        } else if (i == kNumBands - 1) {
          b.svf[pass].Process<FILTER_MODE_HIGH_PASS>(
              source, destination, band_size);
        } else {
          b.svf[pass].Process<FILTER_MODE_BAND_PASS_NORMALIZED>(
              source, destination, band_size);
        }
      }
      // Apply post-gain
      const float gain = b.post_gain;
      float* output = b.samples;
      for (size_t i = 0; i < band_size; ++i) {
        output[i] *= gain;
      }
    }
  }
  
  void FilterBank::Synthesize(float* out, size_t size) {
    float* buffers[3] = { tmp_[1], tmp_[0], out };
  
    fill(&buffers[0][0], &buffers[0][size / band_[0].decimation_factor], 0.0f);
    for (int32_t i = 0; i < kNumBands; ++i) {
      Band& b = band_[i];
      
      size_t band_size = size / b.decimation_factor;
      float* s = buffers[b.group];
      for (size_t j = 0; j < band_size; ++j) {
        s[j] += b.delay_line.ReadWrite(b.samples[j]);
      }
      
      if (band_[i + 1].group != b.group) {
        if (b.group == 0) {
          low_src_up_.Process(tmp_[1], tmp_[0], band_size);
        } else if (b.group == 1) {
          mid_src_up_.Process(tmp_[0], out, band_size);
        }
      }
    }
  }
  
  }  // namespace warps
  