Example of reading (and possibly modifying) a 16 or 32 bit WAV file.

example_wav.c

/**
 * Copyright (c) 2015-2022, Martin Roth ([email protected])
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

// Heavily based on and slightly modified from: https://github.com/mhroth/tinywav

#include "tinywav.h"

#include <assert.h>

#define NUM_CHANNELS 2
#define SAMPLE_RATE 44100
#define BLOCK_SIZE 512

/* Filter coefficient value: A < 1 */
#define A_VALUE ((float)(0.24))

float y_history = 0.0;
// based on: https://www.dsp-weimich.com/digital-signal-processing/iir-first-order-digital-filter/
float IIR_Filter_First_Order(float x_input)
{
  float y_round;
  y_history = y_history + A_VALUE * (((float)x_input - y_history));
  y_round = y_history;
  return y_round;
}

int main(int argc, char *argv[])
{

  char *outputPath = "./tiny_output.wav";

  if (argc < 2)
    return -1;
  const char *inputPath = argv[1];

  fprintf(stderr, "Starting\n");
  TinyWav twReader;

  tinywav_open_read(&twReader, inputPath, TW_INLINE);

  if (twReader.numChannels != NUM_CHANNELS || twReader.h.SampleRate != SAMPLE_RATE)
  {
    fprintf(stderr, "Supplied test wav has wrong format - should be [%d]channels, fs=[%d]\n", NUM_CHANNELS, SAMPLE_RATE);
    return -1;
  }

  TinyWav twWriter;
  tinywav_open_write(&twWriter, NUM_CHANNELS, SAMPLE_RATE, TW_FLOAT32, TW_INLINE, outputPath);

  int totalNumSamples = twReader.numFramesInHeader;
  fprintf(stderr, "%d\n", twReader.numFramesInHeader);

  int samplesProcessed = 0;
  while (samplesProcessed < totalNumSamples)
  {
    float buffer[NUM_CHANNELS * BLOCK_SIZE];

    int samplesRead = tinywav_read_f(&twReader, buffer, BLOCK_SIZE);
    assert(samplesRead > 0 && " Could not read from file!");
    // printf( "%d\n", samplesRead) ;

    // mod code
   /* for (int j = 0 j < 2; J++)
    {
      for (int i = 0; i < samplesRead; i++)
      {
        // buffer[i] = IIR_Filter_First_Order( buffer[i]) ;
        
      }
    }
*/
    int samplesWritten = tinywav_write_f(&twWriter, buffer, samplesRead);
    assert(samplesWritten > 0 && "Could not write to file!");

    samplesProcessed += samplesRead * NUM_CHANNELS;
  }

  tinywav_close_read(&twReader);
  tinywav_close_write(&twWriter);

  return 0;
}