A C program fails to generate a simple WAV file

Programming and Development General Audio Programming
1

I don’t know what would be a better forum to ask this question, so I’ll ask it here. I’ve tried to make a C program which will output a WAV file containing the octave, each note lasting one second. However, for some reason, which I haven’t been able to find for hours now, the WAV file won’t open.

#include <stdint.h>
#include <stdio.h>
#include <math.h>

int main() {
	FILE *wav=fopen("example.wav","wb");
	fprintf(wav,"RIFF");
	const int sampleRate=8192;
	int32_t ChunkSize=36+8*sampleRate*2;
	fwrite(&ChunkSize,4,1,wav);
	fprintf(wav,"WAVEfmt");
	int32_t Subchunk1Size=16; //PCM header is always 16 bytes
	fwrite(&Subchunk1Size,4,1,wav);
	int16_t AudioFormat=1; //PCM
	fwrite(&AudioFormat,2,1,wav);
	int16_t NumChannels=1; //MONO audio.
	fwrite(&NumChannels,2,1,wav);
	int32_t SampleRate=sampleRate;
	fwrite(&SampleRate,4,1,wav);
	int32_t ByteRate=2*sampleRate;
	fwrite(&ByteRate,4,1,wav);
	int16_t BlockAlign=2;
	fwrite(&BlockAlign,2,1,wav);
	int16_t BitsPerSample=16;
	fwrite(&BitsPerSample,2,1,wav);
	fprintf(wav,"data");
	int32_t Subchunk2Size=ChunkSize-36;
	for (int i=0; i<8*sampleRate; i++) {
		float currentFrequency;
		if (i<=sampleRate)
			currentFrequency=262; //The C tone is 262Hz.
		else if (i>sampleRate && i<=2*sampleRate)
			currentFrequency=294; //The D tone is 294Hz.
		else if (i>2*sampleRate && i<=3*sampleRate)
			currentFrequency=330; //The E tone is 330Hz.
		else if (i>3*sampleRate && i<=4*sampleRate)
			currentFrequency=349; //The F tone.
		else if (i>4*sampleRate && i<=5*sampleRate)
			currentFrequency=391; //The G tone.
		else if (i>5*sampleRate && i<=6*sampleRate)
			currentFrequency=440; //The A tone.
		else if (i>6*sampleRate && i<=7*sampleRate)
			currentFrequency=494;  //The H sound.
		else
			currentFrequency=523; //The Tenor C.
		float baseFrequency=sin(2*M_PI*currentFrequency*i/sampleRate)*16384;
		float secondHarmony=sin(2*M_PI*2*currentFrequency*i/sampleRate)*4096;
		float thirdHarmony=sin(2*M_PI*3*currentFrequency*i/sampleRate)*41024;
		float currentAmplitude=baseFrequency+secondHarmony+thirdHarmony*exp(-(float)(i%sampleRate+2000)/2000); 
		int16_t numberToBeWritten=currentAmplitude;
		fwrite(&numberToBeWritten,2,1,wav);
	}
	fclose(wav);
}

Can you guess what’s going on here? I can’t.

2

Solved it myself. Here is the correct program:

#include <stdint.h>
#include <stdio.h>
#include <math.h>

int main() {
	FILE *wav=fopen("example.wav","wb");
	fprintf(wav,"RIFF");
	const int sampleRate=8192;
	int32_t ChunkSize=36+8*sampleRate*2;
	fwrite(&ChunkSize,4,1,wav);
	fprintf(wav,"WAVEfmt "); //This line has been changed!
	int32_t Subchunk1Size=16; //PCM header is always 16 bytes
	fwrite(&Subchunk1Size,4,1,wav);
	int16_t AudioFormat=1; //PCM
	fwrite(&AudioFormat,2,1,wav);
	int16_t NumChannels=1; //MONO audio.
	fwrite(&NumChannels,2,1,wav);
	int32_t SampleRate=sampleRate;
	fwrite(&SampleRate,4,1,wav);
	int32_t ByteRate=2*sampleRate;
	fwrite(&ByteRate,4,1,wav);
	int16_t BlockAlign=2;
	fwrite(&BlockAlign,2,1,wav);
	int16_t BitsPerSample=16;
	fwrite(&BitsPerSample,2,1,wav);
	fprintf(wav,"data");
	int32_t Subchunk2Size=ChunkSize-36;
	for (int i=0; i<8*sampleRate; i++) {
		float currentFrequency;
		if (i<=sampleRate)
			currentFrequency=262; //The C tone is 262Hz.
		else if (i>sampleRate && i<=2*sampleRate)
			currentFrequency=294; //The D tone is 294Hz.
		else if (i>2*sampleRate && i<=3*sampleRate)
			currentFrequency=330; //The E tone is 330Hz.
		else if (i>3*sampleRate && i<=4*sampleRate)
			currentFrequency=349; //The F tone.
		else if (i>4*sampleRate && i<=5*sampleRate)
			currentFrequency=391; //The G tone.
		else if (i>5*sampleRate && i<=6*sampleRate)
			currentFrequency=440; //The A tone.
		else if (i>6*sampleRate && i<=7*sampleRate)
			currentFrequency=494;  //The H sound.
		else
			currentFrequency=523; //The Tenor C.
		float baseFrequency=sin(2*M_PI*currentFrequency*i/sampleRate)*16384;
		float secondHarmony=sin(2*M_PI*2*currentFrequency*i/sampleRate)*4096;
		float thirdHarmony=sin(2*M_PI*3*currentFrequency*i/sampleRate)*41024;
		float currentAmplitude=baseFrequency+secondHarmony+thirdHarmony*exp(-(float)(i%sampleRate+2000)/2000); 
		int16_t numberToBeWritten=currentAmplitude;
		fwrite(&numberToBeWritten,2,1,wav);
	}
	fclose(wav);
}

Basically, I forgot to put the space character somewhere, and the program still compiled, but it didn’t do what it was supposed to do.

3

In case it is of any interest to you, it can be done very easily using Nyquist.

In the Nyquist Prompt, run this code:

;type generate
(setf notes (list C4 D4 E4 F4 G4 A4 B4 C5))
(seqrep (pitch (length notes))
        (osc (nth pitch notes)))