Posted By

Zufolek on 06/07/09

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Last Edited at 06/07/09 09:14am

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Make a Wav file

/ Published in: C

Makes a mono 8-bit (i.e. one byte per sample) wav file, "out.wav" containing a 500 Hertz sine wave signal. 22050 is the sample rate, and 64000 is the total size of audio data in bytes.

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

/* M_PI is declared in math.h */
#define PI M_PI

typedef unsigned int	UI;
typedef unsigned long int	UL;
typedef unsigned short int	US;
typedef unsigned char	UC;
typedef signed int		SI;
typedef signed long int	SL;
typedef signed short int	SS;
typedef signed char	SC;

#define attr(a) __attribute__((a))

#define packed attr(packed)

/* WAV header, 44-byte total */
typedef struct{
 UL riff	packed;
 UL len	packed;
 UL wave	packed;
 UL fmt	packed;
 UL flen	packed;
 US one	packed;
 US chan	packed;
 UL hz	packed;
 UL bpsec	packed;
 US bpsmp	packed;
 US bitpsmp	packed;
 UL dat	packed;
 UL dlen	packed;
}WAVHDR;

int savefile(const char*const s,const void*const m,const int ml){
 FILE*f=fopen(s,"wb");
 int ok=0;
 if(f){
  ok=fwrite(m,1,ml,f)==ml;
  fclose(f);
 }
 return ok;
}

/* "converts" 4-char string to long int */
#define dw(a) (*(UL*)(a))

/* Makes 44-byte header for 8-bit WAV in memory
usage: wavhdr(pointer,sampleRate,dataLength) */

void wavhdr(void*m,UL hz,UL dlen){
 WAVHDR*p=m;
 p->riff=dw("RIFF");
 p->len=dlen+44;
 p->wave=dw("WAVE");
 p->fmt=dw("fmt ");
 p->flen=0x10;
 p->one=1;
 p->chan=1;
 p->hz=hz;
 p->bpsec=hz;
 p->bpsmp=1;
 p->bitpsmp=8;
 p->dat=dw("data");
 p->dlen=dlen;
}

/* returns 8-bit sample for a sine wave */
UC sinewave(UL rate,float freq,UC amp,UL z){
 return sin(z*((PI*2/rate)*freq))*amp+128;
}

/* make arbitrary audio data here */
void makeaud(UC*p,const UL rate,UL z){
 float freq=500;
 UC amp=120;
 while(z--){
  *p++=sinewave(rate,freq,amp,z);
 }
}

/* makes wav file */
void makewav(const UL rate,const UL dlen){
 const UL mlen=dlen+44;
 UC*const m=malloc(mlen);
 if(m){
  wavhdr(m,rate,dlen);
  makeaud(m+44,rate,dlen);
  savefile("out.wav",m,mlen);
 }
}

int main(){
 if(sizeof(WAVHDR)!=44)puts("bad struct");
 makewav(22050,64000);
 return 0;
}

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