Extract raw sample data from .wav files

wav2raw.c

/*
 * wav2raw
 * 
 * Read .wav file and write only the signal values into a .raw file
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define DESC_SIZE 4
#define COPY_SIZE 1024

int32_t big_endian_int(unsigned char *buffer);
void usage(void);

const char riff_hdr[DESC_SIZE + 1] = {'R', 'I', 'F', 'F', '\0'};
const char wave_hdr[DESC_SIZE + 1] = {'W', 'A', 'V', 'E', '\0'};
const char data_hdr[DESC_SIZE + 1] = {'d', 'a', 't', 'a', '\0'};


int main(int argc, char **argv) {
  int32_t file_size;
  unsigned char buf[DESC_SIZE + 1];
  FILE *in_file, *out_file;

  if (argc != 3) {
    usage();
    exit(-1);
  }

  if ((in_file = fopen(argv[1], "rb")) == NULL) {
    printf("Can not open input file '%s'\n", argv[1]);
    exit(-1);
  }

  /* assert RIFF header */
  fread(buf, 1, DESC_SIZE, in_file);
  if (strcmp((char *)buf, riff_hdr)) {
    printf("Invalid RIFF header in input wav file: %s\n", buf);
    exit(-1);
  }

  /* read file size */
  fread(buf, 1, DESC_SIZE, in_file);
  file_size = big_endian_int(buf);
  printf("File size: %d\n", file_size);

  /* assert WAVE header */
  fread(buf, 1, DESC_SIZE, in_file);
  if (strcmp((char *)buf, wave_hdr)) {
    printf("Invalid WAVE header in input wav file: %s\n", buf);
    exit(-1);
  }

  if ((out_file = fopen(argv[2], "wb")) == NULL) {
    printf("Can not open output file '%s'\n", argv[2]);
    exit(-1);
  }


  /* skip chunks and copy only data chunk content to raw file */
  while (fread(buf, 1, DESC_SIZE, in_file)) {
    int is_data_chunk;
    int32_t chunk_size;

    printf("Descriptor: %s, ", buf);
    is_data_chunk = !strcmp((char *)buf, data_hdr);

    fread(buf, 1, DESC_SIZE, in_file);
    chunk_size = big_endian_int(buf);
    printf("size: %d\n", chunk_size);

    if (is_data_chunk) {
      int32_t num_blocks;
      uint16_t trailing_bytes;
      unsigned char copy_buffer[COPY_SIZE];

      printf("Copy data chunk...\n");
      num_blocks = chunk_size / COPY_SIZE;
      trailing_bytes = chunk_size % COPY_SIZE;

      /* blockwise copy <chunk_size> bytes into the .raw file */
      for (int32_t i = 0; i < num_blocks; i++) {
        fread(&copy_buffer, 1, COPY_SIZE, in_file);
        fwrite(&copy_buffer, 1, COPY_SIZE, out_file);
      }

      fread(&copy_buffer, 1, trailing_bytes, in_file);
      fwrite(&copy_buffer, 1, trailing_bytes, out_file);
    }
    else {
      /* skip all other chunks */
      fseek(in_file, chunk_size, SEEK_CUR);
    }
  }

  return 0;
}


int32_t big_endian_int(unsigned char *buffer) {
  return *buffer | (*(buffer + 1) << 8) | (*(buffer + 2) << 16) | (*(buffer + 3) << 24);
}


void usage(void) {
  printf("\nwav2raw - Convert wav files to raw (no header)\n");
  printf("Usage:\n");
  printf("wav2raw INPUTWAV OUTPUTRAW\n\n");
}