sdl-ios-xcode: src/audio/dsp/SDL_dspaudio.c comparison

comparison src/audio/dsp/SDL_dspaudio.c @ 968:4675910b0b7b

Date: Mon, 11 Oct 2004 15:17:27 +0300 (EEST) From: Hannu Savolainen Subject: Re: SDL uses obsolete OSS features I did some work on getting OSS to work better with SDL. There have been some problems with select which should be fixed now. I'm having some problems in understanding what is the purpose of the DSP_WaitAudio() routine. I added a return to the very beginning of this routine and commendted out the define for USE_BLOCKING_WRITES. At least lbreakout2 seems to work as well as earlier. The latencies are the same. An ordinary blocking write does exactly the same thing than DSP_WaitAudio does. So I would recommend using the USE_BLOCKING_WRITES approach and removing everything from the DSP_WaitAudio routine. Also enabling USE_BLOCKING_WRITES makes it possible to simplify DSP_PlayAudio() because you don't need to handle the partial writes (the do-while loop). Attached is a patch against SDL-1.2.7. After these changes SDL will use OSS as it's designed to be used (make it as simple as possible). This code should work with all OSS implementations because it uses only the very fundamental features that have been there since the jurassic times.

author	Sam Lantinga <slouken@libsdl.org>
date	Fri, 12 Nov 2004 21:39:04 +0000
parents	eec28a5278be
children	c5dedfdb4e42

comparison

equal deleted inserted replaced

-:cda407d627a3
+:4675910b0b7b
 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
+Modified in Oct 2004 by Hannu Savolainen
+hannu@opensound.com
 */
 #ifdef SAVE_RCSID
 static char rcsid =
 "@(#) $Id$";
 /* The tag name used by DSP audio */
 #define DSP_DRIVER_NAME         "dsp"
 /* Open the audio device for playback, and don't block if busy */
-/*#define USE_BLOCKING_WRITES*/
 #define OPEN_FLAGS	(O_WRONLY|O_NONBLOCK)
 /* Audio driver functions */
 static int DSP_OpenAudio(_THIS, SDL_AudioSpec *spec);
 static void DSP_WaitAudio(_THIS);
 };
 /* This function waits until it is possible to write a full sound buffer */
 static void DSP_WaitAudio(_THIS)
 {
-	/* Check to see if the thread-parent process is still alive */
+	/* Not needed at all since OSS handles waiting automagically */
-	{ static int cnt = 0;
+}
-		/* Note that this only works with thread implementations
-		   that use a different process id for each thread.
+static void DSP_PlayAudio(_THIS)
-		*/
+{
-		if (parent && (((++cnt)%10) == 0)) { /* Check every 10 loops */
+	if (write(audio_fd, mixbuf, mixlen)==-1)
-			if ( kill(parent, 0) < 0 ) {
+	{
-				this->enabled = 0;
+		perror("Audio write");
-			}
+		this->enabled = 0;
-		}
+	}
-	}
-#ifndef USE_BLOCKING_WRITES /* Not necessary when using blocking writes */
-	/* See if we need to use timed audio synchronization */
-	if ( frame_ticks ) {
-		/* Use timer for general audio synchronization */
-		Sint32 ticks;
-		ticks = ((Sint32)(next_frame - SDL_GetTicks()))-FUDGE_TICKS;
-		if ( ticks > 0 ) {
-			SDL_Delay(ticks);
-		}
-	} else {
-		/* Use select() for audio synchronization */
-		fd_set fdset;
-		struct timeval timeout;
-		FD_ZERO(&fdset);
-		FD_SET(audio_fd, &fdset);
-		timeout.tv_sec = 10;
-		timeout.tv_usec = 0;
 #ifdef DEBUG_AUDIO
-		fprintf(stderr, "Waiting for audio to get ready\n");
+	fprintf(stderr, "Wrote %d bytes of audio data\n", mixlen);
-#endif
-		if ( select(audio_fd+1, NULL, &fdset, NULL, &timeout) <= 0 ) {
-			const char *message =
-			"Audio timeout - buggy audio driver? (disabled)";
-			/* In general we should never print to the screen,
-			   but in this case we have no other way of letting
-			   the user know what happened.
-			*/
-			fprintf(stderr, "SDL: %s\n", message);
-			this->enabled = 0;
-			/* Don't try to close - may hang */
-			audio_fd = -1;
-#ifdef DEBUG_AUDIO
-			fprintf(stderr, "Done disabling audio\n");
-#endif
-		}
-#ifdef DEBUG_AUDIO
-		fprintf(stderr, "Ready!\n");
-#endif
-	}
-#endif /* !USE_BLOCKING_WRITES */
-}
-static void DSP_PlayAudio(_THIS)
-{
-	int written, p=0;
-	/* Write the audio data, checking for EAGAIN on broken audio drivers */
-	do {
-		written = write(audio_fd, &mixbuf[p], mixlen-p);
-		if (written>0)
-		   p += written;
-		if (written == -1 && errno != 0 && errno != EAGAIN && errno != EINTR)
-		{
-		   /* Non recoverable error has occurred. It should be reported!!! */
-		   perror("audio");
-		   break;
-		}
-		if ( p < written || ((written < 0) && ((errno == 0) || (errno == EAGAIN))) ) {
-			SDL_Delay(1);	/* Let a little CPU time go by */
-		}
-	} while ( p < written );
-	/* If timer synchronization is enabled, set the next write frame */
-	if ( frame_ticks ) {
-		next_frame += frame_ticks;
-	}
-	/* If we couldn't write, assume fatal error for now */
-	if ( written < 0 ) {
-		this->enabled = 0;
-	}
-#ifdef DEBUG_AUDIO
-	fprintf(stderr, "Wrote %d bytes of audio data\n", written);
 #endif
 }
 static Uint8 *DSP_GetAudioBuf(_THIS)
 {
 	if ( mixbuf != NULL ) {
 		SDL_FreeAudioMem(mixbuf);
 		mixbuf = NULL;
 	}
 	if ( audio_fd >= 0 ) {
-		int value;
-		ioctl(audio_fd, SNDCTL_DSP_RESET, &value);
 		close(audio_fd);
 		audio_fd = -1;
 	}
-}
-static int DSP_ReopenAudio(_THIS, const char *audiodev, int format,
-						SDL_AudioSpec *spec)
-{
-	int frag_spec;
-	int value;
-	/* Close and then reopen the audio device */
-	close(audio_fd);
-	audio_fd = open(audiodev, O_WRONLY, 0);
-	if ( audio_fd < 0 ) {
-		SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
-		return(-1);
-	}
-	/* Calculate the final parameters for this audio specification */
-	SDL_CalculateAudioSpec(spec);
-	/* Determine the power of two of the fragment size */
-	for ( frag_spec = 0; (0x01<<frag_spec) < spec->size; ++frag_spec );
-	if ( (0x01<<frag_spec) != spec->size ) {
-		SDL_SetError("Fragment size must be a power of two");
-		return(-1);
-	}
-	frag_spec |= 0x00020000;	/* two fragments, for low latency */
-	/* Set the audio buffering parameters */
-#ifdef DEBUG_AUDIO
-	fprintf(stderr, "Requesting %d fragments of size %d\n",
-		(frag_spec >> 16), 1<<(frag_spec&0xFFFF));
-#endif
-	if ( ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0 ) {
-		fprintf(stderr, "Warning: Couldn't set audio fragment size\n");
-	}
-#ifdef DEBUG_AUDIO
-	{ audio_buf_info info;
-	  ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info);
-	  fprintf(stderr, "fragments = %d\n", info.fragments);
-	  fprintf(stderr, "fragstotal = %d\n", info.fragstotal);
-	  fprintf(stderr, "fragsize = %d\n", info.fragsize);
-	  fprintf(stderr, "bytes = %d\n", info.bytes);
-	}
-#endif
-	/* Set the audio format */
-	value = format;
-	if ( (ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) ||
-						(value != format) ) {
-		SDL_SetError("Couldn't set audio format");
-		return(-1);
-	}
-	/* Set the number of channels of output */
-	value = spec->channels;
-#ifdef SNDCTL_DSP_CHANNELS
-	if ( ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &value) < 0 ) {
-#endif
-		value = (spec->channels > 1);
-		ioctl(audio_fd, SNDCTL_DSP_STEREO, &value);
-		value = (value ? 2 : 1);
-#ifdef SNDCTL_DSP_CHANNELS
-	}
-#endif
-	if ( value != spec->channels ) {
-		SDL_SetError("Couldn't set audio channels");
-		return(-1);
-	}
-	/* Set the DSP frequency */
-	value = spec->freq;
-	if ( ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0 ) {
-		SDL_SetError("Couldn't set audio frequency");
-		return(-1);
-	}
-	spec->freq = value;
-	/* We successfully re-opened the audio */
-	return(0);
 }
 static int DSP_OpenAudio(_THIS, SDL_AudioSpec *spec)
 {
 	char audiodev[1024];
 	int format;
 	int value;
+	int frag_spec;
 	Uint16 test_format;
-	/* Reset the timer synchronization flag */
-	frame_ticks = 0.0;
 	/* Open the audio device */
 	audio_fd = SDL_OpenAudioPath(audiodev, sizeof(audiodev), OPEN_FLAGS, 0);
 	if ( audio_fd < 0 ) {
 		SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
 		return(-1);
 	}
 	mixbuf = NULL;
-#ifdef USE_BLOCKING_WRITES
 	/* Make the file descriptor use blocking writes with fcntl() */
 	{ long flags;
 		flags = fcntl(audio_fd, F_GETFL);
 		flags &= ~O_NONBLOCK;
 		if ( fcntl(audio_fd, F_SETFL, flags) < 0 ) {
 			SDL_SetError("Couldn't set audio blocking mode");
 			return(-1);
 		}
 	}
-#endif
 	/* Get a list of supported hardware formats */
 	if ( ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0 ) {
+		perror("SNDCTL_DSP_GETFMTS");
 		SDL_SetError("Couldn't get audio format list");
 		return(-1);
 	}
 	/* Try for a closest match on audio format */
 			case AUDIO_U8:
 				if ( value & AFMT_U8 ) {
 					format = AFMT_U8;
 				}
 				break;
+			case AUDIO_S16LSB:
+				if ( value & AFMT_S16_LE ) {
+					format = AFMT_S16_LE;
+				}
+				break;
+			case AUDIO_S16MSB:
+				if ( value & AFMT_S16_BE ) {
+					format = AFMT_S16_BE;
+				}
+				break;
+#if 0
+/*
+* These formats are not used by any real life systems so they are not
+* needed here.
+*/
 			case AUDIO_S8:
 				if ( value & AFMT_S8 ) {
 					format = AFMT_S8;
 				}
 				break;
-			case AUDIO_S16LSB:
-				if ( value & AFMT_S16_LE ) {
-					format = AFMT_S16_LE;
-				}
-				break;
-			case AUDIO_S16MSB:
-				if ( value & AFMT_S16_BE ) {
-					format = AFMT_S16_BE;
-				}
-				break;
 			case AUDIO_U16LSB:
 				if ( value & AFMT_U16_LE ) {
 					format = AFMT_U16_LE;
 				}
 				break;
 			case AUDIO_U16MSB:
 				if ( value & AFMT_U16_BE ) {
 					format = AFMT_U16_BE;
 				}
 				break;
+#endif
 			default:
 				format = 0;
 				break;
 		}
 		if ( ! format ) {
 	/* Set the audio format */
 	value = format;
 	if ( (ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) ||
 						(value != format) ) {
+		perror("SNDCTL_DSP_SETFMT");
 		SDL_SetError("Couldn't set audio format");
 		return(-1);
 	}
 	/* Set the number of channels of output */
 	value = spec->channels;
-#ifdef SNDCTL_DSP_CHANNELS
 	if ( ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &value) < 0 ) {
-#endif
+		perror("SNDCTL_DSP_CHANNELS");
-		value = (spec->channels > 1);
+		SDL_SetError("Cannot set the number of channels");
-		ioctl(audio_fd, SNDCTL_DSP_STEREO, &value);
+		return(-1);
-		value = (value ? 2 : 1);
+	}
-#ifdef SNDCTL_DSP_CHANNELS
-	}
-#endif
 	spec->channels = value;
-	/* Because some drivers don't allow setting the buffer size
+	/* Set the DSP frequency */
-	   after setting the format, we must re-open the audio device
+	value = spec->freq;
-	   once we know what format and channels are supported
+	if ( ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0 ) {
-	 */
+		perror("SNDCTL_DSP_SPEED");
-	if ( DSP_ReopenAudio(this, audiodev, format, spec) < 0 ) {
+		SDL_SetError("Couldn't set audio frequency");
-		/* Error is set by DSP_ReopenAudio() */
+		return(-1);
-		return(-1);
+	}
-	}
+	spec->freq = value;
+	/* Calculate the final parameters for this audio specification */
+	SDL_CalculateAudioSpec(spec);
+	/* Determine the power of two of the fragment size */
+	for ( frag_spec = 0; (0x01<<frag_spec) < spec->size; ++frag_spec );
+	if ( (0x01<<frag_spec) != spec->size ) {
+		SDL_SetError("Fragment size must be a power of two");
+		return(-1);
+	}
+	frag_spec |= 0x00020000;	/* two fragments, for low latency */
+	/* Set the audio buffering parameters */
+#ifdef DEBUG_AUDIO
+	fprintf(stderr, "Requesting %d fragments of size %d\n",
+		(frag_spec >> 16), 1<<(frag_spec&0xFFFF));
+#endif
+	if ( ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0 ) {
+		perror("SNDCTL_DSP_SETFRAGMENT");
+		fprintf(stderr, "Warning: Couldn't set audio fragment size\n");
+	}
+#ifdef DEBUG_AUDIO
+	{ audio_buf_info info;
+	  ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info);
+	  fprintf(stderr, "fragments = %d\n", info.fragments);
+	  fprintf(stderr, "fragstotal = %d\n", info.fragstotal);
+	  fprintf(stderr, "fragsize = %d\n", info.fragsize);
+	  fprintf(stderr, "bytes = %d\n", info.bytes);
+	}
+#endif
 	/* Allocate mixing buffer */
 	mixlen = spec->size;
 	mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen);
 	if ( mixbuf == NULL ) {
 		return(-1);
 	}
 	memset(mixbuf, spec->silence, spec->size);
-#ifndef USE_BLOCKING_WRITES
-	/* Check to see if we need to use select() workaround */
-	{ char *workaround;
-		workaround = getenv("SDL_DSP_NOSELECT");
-		if ( workaround ) {
-			frame_ticks = (float)(spec->samples*1000)/spec->freq;
-			next_frame = SDL_GetTicks()+frame_ticks;
-		}
-	}
-#endif /* !USE_BLOCKING_WRITES */
 	/* Get the parent process id (we're the parent of the audio thread) */
 	parent = getpid();
 	/* We're ready to rock and roll. :-) */
 	return(0);

Mercurial > sdl-ios-xcode

comparison src/audio/dsp/SDL_dspaudio.c @ 968:4675910b0b7b