src/audio/nto/SDL_nto_audio.c - third_party/sdl - Git at Google

 /*
     SDL - Simple DirectMedia Layer
     Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga

     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.

     This library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Library General Public License for more details.

     You should have received a copy of the GNU Library General Public
     License along with this library; if not, write to the Free
     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

     Sam Lantinga
     slouken@libsdl.org
 */


 /* Allow access to a raw mixing buffer */

 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <signal.h>
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sched.h>
 #include <sys/asoundlib.h>

 #include "SDL_audio.h"
 #include "SDL_error.h"
 #include "SDL_audiomem.h"
 #include "SDL_audio_c.h"
 #include "SDL_timer.h"
 #include "SDL_nto_audio.h"

 /* The tag name used by NTO audio */
 #define DRIVER_NAME         "nto"

 /* default card and device numbers as listed in dev/snd */
 static int card_no = 0;
 static int device_no = 0;

 /* default channel communication parameters */
 #define DEFAULT_CPARAMS_RATE 22050
 #define DEFAULT_CPARAMS_VOICES 1
 #define DEFAULT_CPARAMS_FRAG_SIZE 4096  //was 512
 #define DEFAULT_CPARAMS_FRAGS_MIN 1
 #define DEFAULT_CPARAMS_FRAGS_MAX 1

 /* Open the audio device for playback, and don't block if busy */
 #define OPEN_FLAGS	SND_PCM_OPEN_PLAYBACK

 /* Audio driver functions */
 static int NTO_OpenAudio(_THIS, SDL_AudioSpec *spec);
 static void NTO_WaitAudio(_THIS);
 static void NTO_PlayAudio(_THIS);
 static Uint8 *NTO_GetAudioBuf(_THIS);
 static void NTO_CloseAudio(_THIS);

 static snd_pcm_channel_status_t cstatus;
 static	snd_pcm_channel_params_t cparams;
 static	snd_pcm_channel_setup_t  csetup;

 /* PCM transfer channel parameters initialize function */
 static void init_pcm_cparams(snd_pcm_channel_params_t* cparams)
 {
 	memset(cparams,0,sizeof(snd_pcm_channel_params_t));

 	cparams->channel = SND_PCM_CHANNEL_PLAYBACK;
 	cparams->mode = SND_PCM_MODE_BLOCK;
 	cparams->start_mode = SND_PCM_START_DATA; //_FULL
 	cparams->stop_mode  = SND_PCM_STOP_STOP;
 	cparams->format.format = SND_PCM_SFMT_S16_LE;
 	cparams->format.interleave = 1;
 	cparams->format.rate = DEFAULT_CPARAMS_RATE;
 	cparams->format.voices = DEFAULT_CPARAMS_VOICES;
 	cparams->buf.block.frag_size = DEFAULT_CPARAMS_FRAG_SIZE;
 	cparams->buf.block.frags_min = DEFAULT_CPARAMS_FRAGS_MIN;
 	cparams->buf.block.frags_max = DEFAULT_CPARAMS_FRAGS_MAX;
 }

 /* Audio driver bootstrap functions */

 static int Audio_Available(void)
 /*
 	See if we can open a nonblocking channel.
 	Return value '1' means we can.
 	Return value '0' means we cannot.
 */
 {
 	int available;
 	int rval;
 	snd_pcm_t *handle;

 	available = 0;
 	handle = NULL;

 	//JB modified to take advantage of software mixer
 	rval = snd_pcm_open_preferred(&handle, &card_no, &device_no, OPEN_FLAGS);

 	if (rval >= 0)
 	{
 			available = 1;

         if ((rval = snd_pcm_close(handle)) < 0)
         {
             SDL_SetError("snd_pcm_close failed: %s\n",snd_strerror(rval));
 			available = 0;
         }
 	}
 	else
 	{

        SDL_SetError("snd_pcm_open failed: %s\n", snd_strerror(rval));
 	}

 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"AudioAvailable rtns %d\n", available);
 #endif
 	return(available);
 }

 static void Audio_DeleteDevice(SDL_AudioDevice *device)
 {
 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"Audio_DeleteDevice\n");
 #endif


 	free(device->hidden);
 	free(device);
 }

 static SDL_AudioDevice *Audio_CreateDevice(int devindex)
 {
 	SDL_AudioDevice *this;
 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"Audio_CreateDevice\n");
 #endif
 	/* Initialize all variables that we clean on shutdown */
 	this = (SDL_AudioDevice *)malloc(sizeof(SDL_AudioDevice));
 	if ( this ) {
 		memset(this, 0, (sizeof *this));
 		this->hidden = (struct SDL_PrivateAudioData *)
 				malloc((sizeof *this->hidden));
 	}
 	if ( (this == NULL) || (this->hidden == NULL) ) {
 		SDL_OutOfMemory();
 		if ( this ) {
 			free(this);
 		}
 		return(0);
 	}
 	memset(this->hidden, 0, (sizeof *this->hidden));
 	audio_handle = NULL;

 	/* Set the function pointers */
 	this->OpenAudio = NTO_OpenAudio;
 	this->WaitAudio = NTO_WaitAudio;
 	this->PlayAudio = NTO_PlayAudio;
 	this->GetAudioBuf = NTO_GetAudioBuf;
 	this->CloseAudio = NTO_CloseAudio;

 	this->free = Audio_DeleteDevice;

 	return this;
 }

 /* Don't change the name from "ALSA_bootstrap" - that's how it's called */
 AudioBootStrap ALSA_bootstrap = {
 	DRIVER_NAME, "Neutrino PCM audio",
 	Audio_Available, Audio_CreateDevice
 };

 /* This function waits until it is possible to write a full sound buffer */
 static void NTO_WaitAudio(_THIS)
 {
 	int rval;
 	int totalbytes,roomavail;
 	/*we consider a full sound buffer to be of size pcm_len bytes */

 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"NTO_WaitAudio\n");
 #endif

 	while(1)
 	{
 	memset(&cstatus, 0, sizeof(cstatus));
 	 if( (rval = snd_pcm_plugin_status(audio_handle, &cstatus)) < 0 )
     {
 		 SDL_SetError("snd_pcm_plugin_status failed: %s\n", snd_strerror(rval));
    	    return;
 	}

 	totalbytes = csetup.buf.block.frag_size *csetup.buf.block.frags;
 	roomavail = totalbytes - cstatus.count;

 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"NTO_WaitAudio roomavail %d pcm_len %d\n",roomavail,pcm_len);
 #endif

 	if ((roomavail >= pcm_len) || (roomavail < 0))
 		return;

 		SDL_Delay(10);
 	}

 }


 static void NTO_PlayAudio(_THIS)
 {
     int written, rval;
     int towrite;

 #ifdef DEBUG_AUDIO
 		fprintf(stderr, "NTO_PlayAudio\n");
 #endif

 	if( !this->enabled)
 	   return;

 	towrite = pcm_len;


     /* Write the audio data, checking for EAGAIN (buffer full) and underrun */
     do {
 		written = snd_pcm_plugin_write(audio_handle, pcm_buf, towrite);
 #ifdef DEBUG_AUDIO
 		fprintf(stderr, "NTO_PlayAudio: written = %d towrite = %d\n",written,towrite);
 #endif
 		if (written != towrite)
 		{
 	        if ((errno == EAGAIN) || (errno == EWOULDBLOCK))
 			{
             	SDL_Delay(1);   /* Let a little CPU time go by and try to write again */
 #ifdef DEBUG_AUDIO
 				fprintf(stderr, "errno == EAGAIN written %d\n", written);
 				towrite -= written; //we wrote some data
 #endif
 				continue;
         	}
 			else if((errno == EINVAL) || (errno == EIO))
 			{
 #ifdef DEBUG_AUDIO
 					if(errno == EIO)
 						fprintf(stderr,"snd_pcm_plugin_write failed EIO: %s\n", snd_strerror(written));
 					if(errno == EINVAL)
 						fprintf(stderr,"snd_pcm_plugin_write failed EINVAL: %s\n", snd_strerror(written));

 #endif

 				  memset(&cstatus, 0, sizeof(cstatus));
 		         if( (rval = snd_pcm_plugin_status(audio_handle, &cstatus)) < 0 )
         		 {
 #ifdef DEBUG_AUDIO
 					fprintf(stderr, "snd_pcm_plugin_status failed %s\n",snd_strerror(rval));
 #endif
 		            SDL_SetError("snd_pcm_plugin_status failed: %s\n", snd_strerror(rval));
         		   return;
 		        }

 				if ( (cstatus.status == SND_PCM_STATUS_UNDERRUN) ||
 					(cstatus.status == SND_PCM_STATUS_READY) )
 				{
 #ifdef DEBUG_AUDIO
 					fprintf(stderr, "buffer underrun\n");
 #endif
 					if ( (rval = snd_pcm_plugin_prepare (audio_handle,SND_PCM_CHANNEL_PLAYBACK)) < 0 )
 					{
 #ifdef DEBUG_AUDIO
 						fprintf(stderr, "NTO_PlayAudio: prepare failed %s\n",snd_strerror(rval));
 #endif
 						SDL_SetError("snd_pcm_plugin_prepare failed: %s\n",snd_strerror(rval) );
 						return;
 					}

 				}
  				continue;
 			}
 			else
 			{
 #ifdef DEBUG_AUDIO
 						fprintf(stderr, "NTO_PlayAudio: snd_pcm_plugin_write failed unknown errno %d %s\n",errno, snd_strerror(rval));
 #endif
 				return;

 			}

 		}
 		else
 		{
 			towrite -= written; //we wrote all remaining data
 		}
     } while ( (towrite > 0)  && (this->enabled) );

     /* If we couldn't write, assume fatal error for now */
     if ( towrite != 0 ) {
         this->enabled = 0;
     }
 	return;
 }

 static Uint8 *NTO_GetAudioBuf(_THIS)
 {
  #ifdef DEBUG_AUDIO
 		fprintf(stderr, "NTO_GetAudioBuf: pcm_buf %X\n",(Uint8 *)pcm_buf);
 #endif
 	return(pcm_buf);
 }

 static void NTO_CloseAudio(_THIS)
 {
 	int rval;

 #ifdef DEBUG_AUDIO
 		fprintf(stderr, "NTO_CloseAudio\n");
 #endif

 	 this->enabled = 0;

 	if ( audio_handle != NULL ) {
 		if ((rval = snd_pcm_plugin_flush(audio_handle,SND_PCM_CHANNEL_PLAYBACK)) < 0)
 		{
         	SDL_SetError("snd_pcm_plugin_flush failed: %s\n",snd_strerror(rval));
 			return;
 		}
 		if ((rval = snd_pcm_close(audio_handle)) < 0)
 		{
 			SDL_SetError("snd_pcm_close failed: %s\n",snd_strerror(rval));
 			return;
 		}
 		audio_handle = NULL;
 	}
 }

 static int NTO_OpenAudio(_THIS, SDL_AudioSpec *spec)
 {
 	int rval;
 	int format;
 	Uint16 test_format;
 	int twidth;
 	int found;

 #ifdef DEBUG_AUDIO
 		fprintf(stderr, "NTO_OpenAudio\n");
 #endif

 	audio_handle = NULL;
 	 this->enabled = 0;

 	if ( pcm_buf != NULL ) {
 		free((Uint8 *)pcm_buf);
 		pcm_buf = NULL;
 	}

 	/* initialize channel transfer parameters to default */
 	init_pcm_cparams(&cparams);

 	/* Open the audio device */

 	rval = snd_pcm_open_preferred(&audio_handle, &card_no, &device_no, OPEN_FLAGS);
 	if ( rval < 0 ) {
 		SDL_SetError("snd_pcm_open failed: %s\n", snd_strerror(rval));
 		return(-1);
 	}

     /* set to nonblocking mode */
     if ((rval = snd_pcm_nonblock_mode(audio_handle, 1))<0) //I assume 1 means on
     {
         SDL_SetError("snd_pcm_nonblock_mode failed: %s\n", snd_strerror(rval));
         return(-1);
     }

     /* enable count status parameter */
     if ((rval = snd_pcm_plugin_set_disable(audio_handle, PLUGIN_DISABLE_MMAP))<0)
     {
         SDL_SetError("snd_pcm_plugin_set_disable failed: %s\n", snd_strerror(rval));
         return(-1);
     }


 	/* Try for a closest match on audio format */
 	format = 0;
  	found = 0; // can't use format as SND_PCM_SFMT_U8 = 0 in nto
 	for ( test_format = SDL_FirstAudioFormat(spec->format);	!found ; )

 	{
 #ifdef DEBUG_AUDIO
 		fprintf(stderr, "Trying format 0x%4.4x spec->samples %d\n", test_format,spec->samples);
 #endif
 			/* if match found set format to equivalent ALSA format */
         switch ( test_format ) {
 			case AUDIO_U8:
 				format = SND_PCM_SFMT_U8;
 				cparams.buf.block.frag_size = spec->samples * spec->channels;
 				found = 1;
 				break;
 			case AUDIO_S8:
 				format = SND_PCM_SFMT_S8;
 				cparams.buf.block.frag_size = spec->samples * spec->channels;
 				found = 1;
 				break;
 			case AUDIO_S16LSB:
 				format = SND_PCM_SFMT_S16_LE;
 				cparams.buf.block.frag_size = spec->samples*2 * spec->channels;
 				found = 1;
 				break;
 			case AUDIO_S16MSB:
 				format = SND_PCM_SFMT_S16_BE;
 				cparams.buf.block.frag_size = spec->samples*2 * spec->channels;
 				found = 1;
 				break;
 			case AUDIO_U16LSB:
 				format = SND_PCM_SFMT_U16_LE;
 				cparams.buf.block.frag_size = spec->samples*2 * spec->channels;
 				found = 1;
 				break;
 			case AUDIO_U16MSB:
 				format = SND_PCM_SFMT_U16_BE;
 				cparams.buf.block.frag_size = spec->samples*2 * spec->channels;
 				found = 1;
 				break;
 			default:
 				break;
 		}
 		if ( ! found ) {
 			test_format = SDL_NextAudioFormat();
 		}
 	}

 	/* assumes test_format not 0 on success */
 	if ( test_format == 0 ) {
 		SDL_SetError("Couldn't find any hardware audio formats");
 		return(-1);
 	}

 	spec->format = test_format;

 	/* Set the audio format */
 	cparams.format.format = format;

 	/* Set mono or stereo audio (currently only two channels supported) */
 	cparams.format.voices = spec->channels;

 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"intializing channels %d\n", cparams.format.voices);
 #endif


 	/* Set rate */
 	cparams.format.rate = spec->freq ;

 	/* Setup the transfer parameters according to cparams */
 	rval = snd_pcm_plugin_params(audio_handle, &cparams);
 	if (rval < 0) {
 		SDL_SetError("snd_pcm_channel_params failed: %s\n", snd_strerror (rval));
 		return(-1);
 	}

     /*  Make sure channel is setup right one last time */
     memset( &csetup, 0, sizeof( csetup ) );
     csetup.channel = SND_PCM_CHANNEL_PLAYBACK;
     if ( snd_pcm_plugin_setup( audio_handle, &csetup ) < 0 )
     {
         SDL_SetError("Unable to setup playback channel\n" );
         return(-1);
     }
     else
     {
 #ifdef DEBUG_AUDIO
         fprintf(stderr,"requested format: %d\n",cparams.format.format);
         fprintf(stderr,"requested frag size: %d\n",cparams.buf.block.frag_size);
         fprintf(stderr,"requested max frags: %d\n\n",cparams.buf.block.frags_max);

         fprintf(stderr,"real format: %d\n", csetup.format.format );
         fprintf(stderr,"real frag size : %d\n", csetup.buf.block.frag_size );
 		fprintf(stderr,"real max frags : %d\n", csetup.buf.block.frags_max );
 #endif // DEBUG_AUDIO
     }


     /*  Allocate memory to the audio buffer and initialize with silence
         (Note that buffer size must be a multiple of fragment size, so find closest multiple)
     */

     twidth = snd_pcm_format_width(format);
     if (twidth < 0) {
         printf("snd_pcm_format_width failed\n");
         twidth = 0;
     }

 #ifdef DEBUG_AUDIO
     fprintf(stderr,"format is %d bits wide\n",twidth);
 #endif

     pcm_len = spec->size ;


 #ifdef DEBUG_AUDIO
     fprintf(stderr,"pcm_len set to %d\n", pcm_len);
 #endif

     if (pcm_len == 0)
     {
         pcm_len = csetup.buf.block.frag_size;
     }

     pcm_buf = (Uint8*)malloc(pcm_len);
     if (pcm_buf == NULL) {
         SDL_SetError("pcm_buf malloc failed\n");
         return(-1);
     }
     memset(pcm_buf,spec->silence,pcm_len);

 #ifdef DEBUG_AUDIO
 	fprintf(stderr,"pcm_buf malloced and silenced.\n");
 #endif

     /* get the file descriptor */
     if( (audio_fd = snd_pcm_file_descriptor(audio_handle, SND_PCM_CHANNEL_PLAYBACK)) < 0)
     {
        fprintf(stderr, "snd_pcm_file_descriptor failed with error code: %d\n", audio_fd);
     }

 	/* Trigger audio playback */
 	rval = snd_pcm_plugin_prepare( audio_handle, SND_PCM_CHANNEL_PLAYBACK);
 	if (rval < 0) {
        SDL_SetError("snd_pcm_plugin_prepare failed: %s\n", snd_strerror (rval));
        return(-1);
 	}

 	 this->enabled = 1;

 	/* Get the parent process id (we're the parent of the audio thread) */
 	parent = getpid();

 	/* We're ready to rock and roll. :-) */
 	return(0);
 }
	/*
	SDL - Simple DirectMedia Layer
	Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga

	This library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Library General Public
	License as published by the Free Software Foundation; either
	version 2 of the License, or (at your option) any later version.

	This library is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	Library General Public License for more details.

	You should have received a copy of the GNU Library General Public
	License along with this library; if not, write to the Free
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

	Sam Lantinga
	slouken@libsdl.org
	*/



	/* Allow access to a raw mixing buffer */

	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <errno.h>
	#include <unistd.h>
	#include <fcntl.h>
	#include <signal.h>
	#include <sys/types.h>
	#include <sys/time.h>
	#include <sched.h>
	#include <sys/asoundlib.h>

	#include "SDL_audio.h"
	#include "SDL_error.h"
	#include "SDL_audiomem.h"
	#include "SDL_audio_c.h"
	#include "SDL_timer.h"
	#include "SDL_nto_audio.h"

	/* The tag name used by NTO audio */
	#define DRIVER_NAME "nto"

	/* default card and device numbers as listed in dev/snd */
	static int card_no = 0;
	static int device_no = 0;

	/* default channel communication parameters */
	#define DEFAULT_CPARAMS_RATE 22050
	#define DEFAULT_CPARAMS_VOICES 1
	#define DEFAULT_CPARAMS_FRAG_SIZE 4096 //was 512
	#define DEFAULT_CPARAMS_FRAGS_MIN 1
	#define DEFAULT_CPARAMS_FRAGS_MAX 1

	/* Open the audio device for playback, and don't block if busy */
	#define OPEN_FLAGS SND_PCM_OPEN_PLAYBACK

	/* Audio driver functions */
	static int NTO_OpenAudio(_THIS, SDL_AudioSpec *spec);
	static void NTO_WaitAudio(_THIS);
	static void NTO_PlayAudio(_THIS);
	static Uint8 *NTO_GetAudioBuf(_THIS);
	static void NTO_CloseAudio(_THIS);

	static snd_pcm_channel_status_t cstatus;
	static snd_pcm_channel_params_t cparams;
	static snd_pcm_channel_setup_t csetup;

	/* PCM transfer channel parameters initialize function */
	static void init_pcm_cparams(snd_pcm_channel_params_t* cparams)
	{
	memset(cparams,0,sizeof(snd_pcm_channel_params_t));

	cparams->channel = SND_PCM_CHANNEL_PLAYBACK;
	cparams->mode = SND_PCM_MODE_BLOCK;
	cparams->start_mode = SND_PCM_START_DATA; //_FULL
	cparams->stop_mode = SND_PCM_STOP_STOP;
	cparams->format.format = SND_PCM_SFMT_S16_LE;
	cparams->format.interleave = 1;
	cparams->format.rate = DEFAULT_CPARAMS_RATE;
	cparams->format.voices = DEFAULT_CPARAMS_VOICES;
	cparams->buf.block.frag_size = DEFAULT_CPARAMS_FRAG_SIZE;
	cparams->buf.block.frags_min = DEFAULT_CPARAMS_FRAGS_MIN;
	cparams->buf.block.frags_max = DEFAULT_CPARAMS_FRAGS_MAX;
	}

	/* Audio driver bootstrap functions */

	static int Audio_Available(void)
	/*
	See if we can open a nonblocking channel.
	Return value '1' means we can.
	Return value '0' means we cannot.
	*/
	{
	int available;
	int rval;
	snd_pcm_t *handle;

	available = 0;
	handle = NULL;

	//JB modified to take advantage of software mixer
	rval = snd_pcm_open_preferred(&handle, &card_no, &device_no, OPEN_FLAGS);

	if (rval >= 0)
	{
	available = 1;

	if ((rval = snd_pcm_close(handle)) < 0)
	{
	SDL_SetError("snd_pcm_close failed: %s\n",snd_strerror(rval));
	available = 0;
	}
	}
	else
	{

	SDL_SetError("snd_pcm_open failed: %s\n", snd_strerror(rval));
	}

	#ifdef DEBUG_AUDIO
	fprintf(stderr,"AudioAvailable rtns %d\n", available);
	#endif
	return(available);
	}

	static void Audio_DeleteDevice(SDL_AudioDevice *device)
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr,"Audio_DeleteDevice\n");
	#endif


	free(device->hidden);
	free(device);
	}

	static SDL_AudioDevice *Audio_CreateDevice(int devindex)
	{
	SDL_AudioDevice *this;
	#ifdef DEBUG_AUDIO
	fprintf(stderr,"Audio_CreateDevice\n");
	#endif
	/* Initialize all variables that we clean on shutdown */
	this = (SDL_AudioDevice *)malloc(sizeof(SDL_AudioDevice));
	if ( this ) {
	memset(this, 0, (sizeof *this));
	this->hidden = (struct SDL_PrivateAudioData *)
	malloc((sizeof *this->hidden));
	}
	if ( (this == NULL) \|\| (this->hidden == NULL) ) {
	SDL_OutOfMemory();
	if ( this ) {
	free(this);
	}
	return(0);
	}
	memset(this->hidden, 0, (sizeof *this->hidden));
	audio_handle = NULL;

	/* Set the function pointers */
	this->OpenAudio = NTO_OpenAudio;
	this->WaitAudio = NTO_WaitAudio;
	this->PlayAudio = NTO_PlayAudio;
	this->GetAudioBuf = NTO_GetAudioBuf;
	this->CloseAudio = NTO_CloseAudio;

	this->free = Audio_DeleteDevice;

	return this;
	}

	/* Don't change the name from "ALSA_bootstrap" - that's how it's called */
	AudioBootStrap ALSA_bootstrap = {
	DRIVER_NAME, "Neutrino PCM audio",
	Audio_Available, Audio_CreateDevice
	};

	/* This function waits until it is possible to write a full sound buffer */
	static void NTO_WaitAudio(_THIS)
	{
	int rval;
	int totalbytes,roomavail;
	/we consider a full sound buffer to be of size pcm_len bytes /

	#ifdef DEBUG_AUDIO
	fprintf(stderr,"NTO_WaitAudio\n");
	#endif

	while(1)
	{
	memset(&cstatus, 0, sizeof(cstatus));
	if( (rval = snd_pcm_plugin_status(audio_handle, &cstatus)) < 0 )
	{
	SDL_SetError("snd_pcm_plugin_status failed: %s\n", snd_strerror(rval));
	return;
	}

	totalbytes = csetup.buf.block.frag_size *csetup.buf.block.frags;
	roomavail = totalbytes - cstatus.count;

	#ifdef DEBUG_AUDIO
	fprintf(stderr,"NTO_WaitAudio roomavail %d pcm_len %d\n",roomavail,pcm_len);
	#endif

	if ((roomavail >= pcm_len) \|\| (roomavail < 0))
	return;

	SDL_Delay(10);
	}

	}



	static void NTO_PlayAudio(_THIS)
	{
	int written, rval;
	int towrite;

	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_PlayAudio\n");
	#endif

	if( !this->enabled)
	return;

	towrite = pcm_len;


	/* Write the audio data, checking for EAGAIN (buffer full) and underrun */
	do {
	written = snd_pcm_plugin_write(audio_handle, pcm_buf, towrite);
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_PlayAudio: written = %d towrite = %d\n",written,towrite);
	#endif
	if (written != towrite)
	{
	if ((errno == EAGAIN) \|\| (errno == EWOULDBLOCK))
	{
	SDL_Delay(1); /* Let a little CPU time go by and try to write again */
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "errno == EAGAIN written %d\n", written);
	towrite -= written; //we wrote some data
	#endif
	continue;
	}
	else if((errno == EINVAL) \|\| (errno == EIO))
	{
	#ifdef DEBUG_AUDIO
	if(errno == EIO)
	fprintf(stderr,"snd_pcm_plugin_write failed EIO: %s\n", snd_strerror(written));
	if(errno == EINVAL)
	fprintf(stderr,"snd_pcm_plugin_write failed EINVAL: %s\n", snd_strerror(written));

	#endif

	memset(&cstatus, 0, sizeof(cstatus));
	if( (rval = snd_pcm_plugin_status(audio_handle, &cstatus)) < 0 )
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "snd_pcm_plugin_status failed %s\n",snd_strerror(rval));
	#endif
	SDL_SetError("snd_pcm_plugin_status failed: %s\n", snd_strerror(rval));
	return;
	}

	if ( (cstatus.status == SND_PCM_STATUS_UNDERRUN) \|\|
	(cstatus.status == SND_PCM_STATUS_READY) )
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "buffer underrun\n");
	#endif
	if ( (rval = snd_pcm_plugin_prepare (audio_handle,SND_PCM_CHANNEL_PLAYBACK)) < 0 )
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_PlayAudio: prepare failed %s\n",snd_strerror(rval));
	#endif
	SDL_SetError("snd_pcm_plugin_prepare failed: %s\n",snd_strerror(rval) );
	return;
	}

	}
	continue;
	}
	else
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_PlayAudio: snd_pcm_plugin_write failed unknown errno %d %s\n",errno, snd_strerror(rval));
	#endif
	return;

	}

	}
	else
	{
	towrite -= written; //we wrote all remaining data
	}
	} while ( (towrite > 0) && (this->enabled) );

	/* If we couldn't write, assume fatal error for now */
	if ( towrite != 0 ) {
	this->enabled = 0;
	}
	return;
	}

	static Uint8 *NTO_GetAudioBuf(_THIS)
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_GetAudioBuf: pcm_buf %X\n",(Uint8 *)pcm_buf);
	#endif
	return(pcm_buf);
	}

	static void NTO_CloseAudio(_THIS)
	{
	int rval;

	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_CloseAudio\n");
	#endif

	this->enabled = 0;

	if ( audio_handle != NULL ) {
	if ((rval = snd_pcm_plugin_flush(audio_handle,SND_PCM_CHANNEL_PLAYBACK)) < 0)
	{
	SDL_SetError("snd_pcm_plugin_flush failed: %s\n",snd_strerror(rval));
	return;
	}
	if ((rval = snd_pcm_close(audio_handle)) < 0)
	{
	SDL_SetError("snd_pcm_close failed: %s\n",snd_strerror(rval));
	return;
	}
	audio_handle = NULL;
	}
	}

	static int NTO_OpenAudio(_THIS, SDL_AudioSpec *spec)
	{
	int rval;
	int format;
	Uint16 test_format;
	int twidth;
	int found;

	#ifdef DEBUG_AUDIO
	fprintf(stderr, "NTO_OpenAudio\n");
	#endif

	audio_handle = NULL;
	this->enabled = 0;

	if ( pcm_buf != NULL ) {
	free((Uint8 *)pcm_buf);
	pcm_buf = NULL;
	}

	/* initialize channel transfer parameters to default */
	init_pcm_cparams(&cparams);

	/* Open the audio device */

	rval = snd_pcm_open_preferred(&audio_handle, &card_no, &device_no, OPEN_FLAGS);
	if ( rval < 0 ) {
	SDL_SetError("snd_pcm_open failed: %s\n", snd_strerror(rval));
	return(-1);
	}

	/* set to nonblocking mode */
	if ((rval = snd_pcm_nonblock_mode(audio_handle, 1))<0) //I assume 1 means on
	{
	SDL_SetError("snd_pcm_nonblock_mode failed: %s\n", snd_strerror(rval));
	return(-1);
	}

	/* enable count status parameter */
	if ((rval = snd_pcm_plugin_set_disable(audio_handle, PLUGIN_DISABLE_MMAP))<0)
	{
	SDL_SetError("snd_pcm_plugin_set_disable failed: %s\n", snd_strerror(rval));
	return(-1);
	}


	/* Try for a closest match on audio format */
	format = 0;
	found = 0; // can't use format as SND_PCM_SFMT_U8 = 0 in nto
	for ( test_format = SDL_FirstAudioFormat(spec->format); !found ; )

	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr, "Trying format 0x%4.4x spec->samples %d\n", test_format,spec->samples);
	#endif
	/* if match found set format to equivalent ALSA format */
	switch ( test_format ) {
	case AUDIO_U8:
	format = SND_PCM_SFMT_U8;
	cparams.buf.block.frag_size = spec->samples * spec->channels;
	found = 1;
	break;
	case AUDIO_S8:
	format = SND_PCM_SFMT_S8;
	cparams.buf.block.frag_size = spec->samples * spec->channels;
	found = 1;
	break;
	case AUDIO_S16LSB:
	format = SND_PCM_SFMT_S16_LE;
	cparams.buf.block.frag_size = spec->samples2 spec->channels;
	found = 1;
	break;
	case AUDIO_S16MSB:
	format = SND_PCM_SFMT_S16_BE;
	cparams.buf.block.frag_size = spec->samples2 spec->channels;
	found = 1;
	break;
	case AUDIO_U16LSB:
	format = SND_PCM_SFMT_U16_LE;
	cparams.buf.block.frag_size = spec->samples2 spec->channels;
	found = 1;
	break;
	case AUDIO_U16MSB:
	format = SND_PCM_SFMT_U16_BE;
	cparams.buf.block.frag_size = spec->samples2 spec->channels;
	found = 1;
	break;
	default:
	break;
	}
	if ( ! found ) {
	test_format = SDL_NextAudioFormat();
	}
	}

	/* assumes test_format not 0 on success */
	if ( test_format == 0 ) {
	SDL_SetError("Couldn't find any hardware audio formats");
	return(-1);
	}

	spec->format = test_format;

	/* Set the audio format */
	cparams.format.format = format;

	/* Set mono or stereo audio (currently only two channels supported) */
	cparams.format.voices = spec->channels;

	#ifdef DEBUG_AUDIO
	fprintf(stderr,"intializing channels %d\n", cparams.format.voices);
	#endif


	/* Set rate */
	cparams.format.rate = spec->freq ;

	/* Setup the transfer parameters according to cparams */
	rval = snd_pcm_plugin_params(audio_handle, &cparams);
	if (rval < 0) {
	SDL_SetError("snd_pcm_channel_params failed: %s\n", snd_strerror (rval));
	return(-1);
	}

	/* Make sure channel is setup right one last time */
	memset( &csetup, 0, sizeof( csetup ) );
	csetup.channel = SND_PCM_CHANNEL_PLAYBACK;
	if ( snd_pcm_plugin_setup( audio_handle, &csetup ) < 0 )
	{
	SDL_SetError("Unable to setup playback channel\n" );
	return(-1);
	}
	else
	{
	#ifdef DEBUG_AUDIO
	fprintf(stderr,"requested format: %d\n",cparams.format.format);
	fprintf(stderr,"requested frag size: %d\n",cparams.buf.block.frag_size);
	fprintf(stderr,"requested max frags: %d\n\n",cparams.buf.block.frags_max);

	fprintf(stderr,"real format: %d\n", csetup.format.format );
	fprintf(stderr,"real frag size : %d\n", csetup.buf.block.frag_size );
	fprintf(stderr,"real max frags : %d\n", csetup.buf.block.frags_max );
	#endif // DEBUG_AUDIO
	}


	/* Allocate memory to the audio buffer and initialize with silence
	(Note that buffer size must be a multiple of fragment size, so find closest multiple)
	*/

	twidth = snd_pcm_format_width(format);
	if (twidth < 0) {
	printf("snd_pcm_format_width failed\n");
	twidth = 0;
	}

	#ifdef DEBUG_AUDIO
	fprintf(stderr,"format is %d bits wide\n",twidth);
	#endif

	pcm_len = spec->size ;


	#ifdef DEBUG_AUDIO
	fprintf(stderr,"pcm_len set to %d\n", pcm_len);
	#endif

	if (pcm_len == 0)
	{
	pcm_len = csetup.buf.block.frag_size;
	}

	pcm_buf = (Uint8*)malloc(pcm_len);
	if (pcm_buf == NULL) {
	SDL_SetError("pcm_buf malloc failed\n");
	return(-1);
	}
	memset(pcm_buf,spec->silence,pcm_len);

	#ifdef DEBUG_AUDIO
	fprintf(stderr,"pcm_buf malloced and silenced.\n");
	#endif

	/* get the file descriptor */
	if( (audio_fd = snd_pcm_file_descriptor(audio_handle, SND_PCM_CHANNEL_PLAYBACK)) < 0)
	{
	fprintf(stderr, "snd_pcm_file_descriptor failed with error code: %d\n", audio_fd);
	}

	/* Trigger audio playback */
	rval = snd_pcm_plugin_prepare( audio_handle, SND_PCM_CHANNEL_PLAYBACK);
	if (rval < 0) {
	SDL_SetError("snd_pcm_plugin_prepare failed: %s\n", snd_strerror (rval));
	return(-1);
	}

	this->enabled = 1;

	/* Get the parent process id (we're the parent of the audio thread) */
	parent = getpid();

	/* We're ready to rock and roll. :-) */
	return(0);
	}