/*
	oss.c plays a raw PCM 22KHz sample sound on the sound card
	
	Important  -  Make sure the demo.pcm file is is the current directory
	before you attempt to run this program.

	Disclaimer - I'm in no way responsible if you screw up your system
	trying to run this example.	
*/

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/soundcard.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>

#define SECONDS 5 //playback seconds

int main() 
{
	int fd;
	int handle = -1;
	int channels = 1;         // 0=mono 1=stereo
	int format = AFMT_U8;
	int rate = 22000;
	unsigned char* data;
	
/* Open the file corresponding to the soundcard for writing, DSP stands for Digital Signal Processor */
	if ( (handle = open("/dev/dsp",O_WRONLY)) == -1 )
	{
		perror("open /dev/dsp");
		return -1;
	}
/* Tell the sound card that the sound about to be played is stereo. 0=mono 1=stereo */

	if ( ioctl(handle, SNDCTL_DSP_STEREO,&channels) == -1 )
	{
		perror("ioctl stereo");
		return errno;
	}

	/* Inform the sound card of the audio format */
	if ( ioctl(handle, SNDCTL_DSP_SETFMT,&format) == -1 )
	{
		perror("ioctl format");
		return errno;
	}
	
	/* Set the DSP playback rate, sampling rate of the raw PCM audio */
	if (ioctl(handle, SNDCTL_DSP_SPEED,&rate) == -1 )
	{
		perror("ioctl sample rate");
		return errno;
	}
   
	// rate * 5 seconds * two channels
	data = malloc(rate*SECONDS*(channels+1));
	
	if((fd=open("demo.pcm",O_RDONLY))==-1)
	{
		perror("open file");
		exit(-1);
	}

	/* read the data contained in the demo file to the allocated memory */
	read(fd,data,rate*SECONDS*(channels+1));
	close(fd);
	
	/* just write the data to the sound card! This will play it. */

	write(handle, data, rate*SECONDS*(channels+1));

	if (ioctl(handle, SNDCTL_DSP_SYNC) == -1)
	{
		perror("ioctl sync");
		return errno;
    	}

	free(data); //Be good, clean up.
	close(handle);
	printf("\nDone\n");
	return 0;
}