text: /* 
   * Sample Rate Converter
   *
   * Copyright 2019 Wenting Zhang
   * 
   * Redistribution and use in source and binary forms, with or without 
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, 
   *    this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice, 
   *    this list of conditions and the following disclaimer in the documentation 
   *    and/or other materials provided with the distribution.
   *
   * 3. Neither the name of the copyright holder nor the names of its contributors
   *    may be used to endorse or promote products derived from this software 
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
   * POSSIBILITY OF SUCH DAMAGE. 
   */
  #ifndef __SRC_H__
  #define __SRC_H__
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #ifndef M_PI
  #define M_PI 3.14159265358979323846
  #endif
  
  typedef enum {
      FIR_LOWPASS,
      FIR_HIGHPASS,
      FIR_BANDPASS,
      FIR_BANDSTOP
  } FIR_Response;
  
  typedef struct {
      float* pfb;
      int num_phases;
      int taps_per_phase;
      int interpolation;
      int decimation;
      int phase_index;
      int input_deficit;
      float* history;
      int history_length;
  } FIR_Filter;
  
  float* src_generate_fir_coeffs(int num_taps, float cutoff);
  FIR_Filter* src_generate_fir_filter(float* coefficients, int num_taps,
          int interpolation, int decimation);
  FIR_Filter* src_generate(int interpolation, int decimation);
  int src_filt(FIR_Filter* filter, float* samples, int count, float* p_output);
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif