SDL_dspaudio.c revision 9682c8870b8ff5e4ac2e4c70b759f791c6f38c1f 
1/*
2    SDL - Simple DirectMedia Layer
3    Copyright (C) 1997-2012 Sam Lantinga
4
5    This library is free software; you can redistribute it and/or
6    modify it under the terms of the GNU Lesser General Public
7    License as published by the Free Software Foundation; either
8    version 2.1 of the License, or (at your option) any later version.
9
10    This library is distributed in the hope that it will be useful,
11    but WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13    Lesser General Public License for more details.
14
15    You should have received a copy of the GNU Lesser General Public
16    License along with this library; if not, write to the Free Software
17    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
18
19    Sam Lantinga
20    slouken@libsdl.org
21
22    Modified in Oct 2004 by Hannu Savolainen
23    hannu@opensound.com
24*/
25#include "SDL_config.h"
26
27/* Allow access to a raw mixing buffer */
28
29#include <stdio.h>	/* For perror() */
30#include <string.h>	/* For strerror() */
31#include <errno.h>
32#include <unistd.h>
33#include <fcntl.h>
34#include <signal.h>
35#include <sys/time.h>
36#include <sys/ioctl.h>
37#include <sys/stat.h>
38
39#if SDL_AUDIO_DRIVER_OSS_SOUNDCARD_H
40/* This is installed on some systems */
41#include <soundcard.h>
42#else
43/* This is recommended by OSS */
44#include <sys/soundcard.h>
45#endif
46
47#include "SDL_timer.h"
48#include "SDL_audio.h"
49#include "../SDL_audiomem.h"
50#include "../SDL_audio_c.h"
51#include "../SDL_audiodev_c.h"
52#include "SDL_dspaudio.h"
53
54/* The tag name used by DSP audio */
55#define DSP_DRIVER_NAME         "dsp"
56
57/* Open the audio device for playback, and don't block if busy */
58#define OPEN_FLAGS	(O_WRONLY|O_NONBLOCK)
59
60/* Audio driver functions */
61static int DSP_OpenAudio(_THIS, SDL_AudioSpec *spec);
62static void DSP_WaitAudio(_THIS);
63static void DSP_PlayAudio(_THIS);
64static Uint8 *DSP_GetAudioBuf(_THIS);
65static void DSP_CloseAudio(_THIS);
66
67/* Audio driver bootstrap functions */
68
69static int Audio_Available(void)
70{
71	int fd;
72	int available;
73
74	available = 0;
75	fd = SDL_OpenAudioPath(NULL, 0, OPEN_FLAGS, 0);
76	if ( fd >= 0 ) {
77		available = 1;
78		close(fd);
79	}
80	return(available);
81}
82
83static void Audio_DeleteDevice(SDL_AudioDevice *device)
84{
85	SDL_free(device->hidden);
86	SDL_free(device);
87}
88
89static SDL_AudioDevice *Audio_CreateDevice(int devindex)
90{
91	SDL_AudioDevice *this;
92
93	/* Initialize all variables that we clean on shutdown */
94	this = (SDL_AudioDevice *)SDL_malloc(sizeof(SDL_AudioDevice));
95	if ( this ) {
96		SDL_memset(this, 0, (sizeof *this));
97		this->hidden = (struct SDL_PrivateAudioData *)
98				SDL_malloc((sizeof *this->hidden));
99	}
100	if ( (this == NULL) || (this->hidden == NULL) ) {
101		SDL_OutOfMemory();
102		if ( this ) {
103			SDL_free(this);
104		}
105		return(0);
106	}
107	SDL_memset(this->hidden, 0, (sizeof *this->hidden));
108	audio_fd = -1;
109
110	/* Set the function pointers */
111	this->OpenAudio = DSP_OpenAudio;
112	this->WaitAudio = DSP_WaitAudio;
113	this->PlayAudio = DSP_PlayAudio;
114	this->GetAudioBuf = DSP_GetAudioBuf;
115	this->CloseAudio = DSP_CloseAudio;
116
117	this->free = Audio_DeleteDevice;
118
119	return this;
120}
121
122AudioBootStrap DSP_bootstrap = {
123	DSP_DRIVER_NAME, "OSS /dev/dsp standard audio",
124	Audio_Available, Audio_CreateDevice
125};
126
127/* This function waits until it is possible to write a full sound buffer */
128static void DSP_WaitAudio(_THIS)
129{
130	/* Not needed at all since OSS handles waiting automagically */
131}
132
133static void DSP_PlayAudio(_THIS)
134{
135	if (write(audio_fd, mixbuf, mixlen)==-1)
136	{
137		perror("Audio write");
138		this->enabled = 0;
139	}
140
141#ifdef DEBUG_AUDIO
142	fprintf(stderr, "Wrote %d bytes of audio data\n", mixlen);
143#endif
144}
145
146static Uint8 *DSP_GetAudioBuf(_THIS)
147{
148	return(mixbuf);
149}
150
151static void DSP_CloseAudio(_THIS)
152{
153	if ( mixbuf != NULL ) {
154		SDL_FreeAudioMem(mixbuf);
155		mixbuf = NULL;
156	}
157	if ( audio_fd >= 0 ) {
158		close(audio_fd);
159		audio_fd = -1;
160	}
161}
162
163static int DSP_OpenAudio(_THIS, SDL_AudioSpec *spec)
164{
165	char audiodev[1024];
166	int format;
167	int value;
168	int frag_spec;
169	Uint16 test_format;
170
171    /* Make sure fragment size stays a power of 2, or OSS fails. */
172    /* I don't know which of these are actually legal values, though... */
173    if (spec->channels > 8)
174        spec->channels = 8;
175    else if (spec->channels > 4)
176        spec->channels = 4;
177    else if (spec->channels > 2)
178        spec->channels = 2;
179
180	/* Open the audio device */
181	audio_fd = SDL_OpenAudioPath(audiodev, sizeof(audiodev), OPEN_FLAGS, 0);
182	if ( audio_fd < 0 ) {
183		SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
184		return(-1);
185	}
186	mixbuf = NULL;
187
188	/* Make the file descriptor use blocking writes with fcntl() */
189	{ long flags;
190		flags = fcntl(audio_fd, F_GETFL);
191		flags &= ~O_NONBLOCK;
192		if ( fcntl(audio_fd, F_SETFL, flags) < 0 ) {
193			SDL_SetError("Couldn't set audio blocking mode");
194			DSP_CloseAudio(this);
195			return(-1);
196		}
197	}
198
199	/* Get a list of supported hardware formats */
200	if ( ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0 ) {
201		perror("SNDCTL_DSP_GETFMTS");
202		SDL_SetError("Couldn't get audio format list");
203		DSP_CloseAudio(this);
204		return(-1);
205	}
206
207	/* Try for a closest match on audio format */
208	format = 0;
209	for ( test_format = SDL_FirstAudioFormat(spec->format);
210						! format && test_format; ) {
211#ifdef DEBUG_AUDIO
212		fprintf(stderr, "Trying format 0x%4.4x\n", test_format);
213#endif
214		switch ( test_format ) {
215			case AUDIO_U8:
216				if ( value & AFMT_U8 ) {
217					format = AFMT_U8;
218				}
219				break;
220			case AUDIO_S16LSB:
221				if ( value & AFMT_S16_LE ) {
222					format = AFMT_S16_LE;
223				}
224				break;
225			case AUDIO_S16MSB:
226				if ( value & AFMT_S16_BE ) {
227					format = AFMT_S16_BE;
228				}
229				break;
230#if 0
231/*
232 * These formats are not used by any real life systems so they are not
233 * needed here.
234 */
235			case AUDIO_S8:
236				if ( value & AFMT_S8 ) {
237					format = AFMT_S8;
238				}
239				break;
240			case AUDIO_U16LSB:
241				if ( value & AFMT_U16_LE ) {
242					format = AFMT_U16_LE;
243				}
244				break;
245			case AUDIO_U16MSB:
246				if ( value & AFMT_U16_BE ) {
247					format = AFMT_U16_BE;
248				}
249				break;
250#endif
251			default:
252				format = 0;
253				break;
254		}
255		if ( ! format ) {
256			test_format = SDL_NextAudioFormat();
257		}
258	}
259	if ( format == 0 ) {
260		SDL_SetError("Couldn't find any hardware audio formats");
261		DSP_CloseAudio(this);
262		return(-1);
263	}
264	spec->format = test_format;
265
266	/* Set the audio format */
267	value = format;
268	if ( (ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) ||
269						(value != format) ) {
270		perror("SNDCTL_DSP_SETFMT");
271		SDL_SetError("Couldn't set audio format");
272		DSP_CloseAudio(this);
273		return(-1);
274	}
275
276	/* Set the number of channels of output */
277	value = spec->channels;
278	if ( ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &value) < 0 ) {
279		perror("SNDCTL_DSP_CHANNELS");
280		SDL_SetError("Cannot set the number of channels");
281		DSP_CloseAudio(this);
282		return(-1);
283	}
284	spec->channels = value;
285
286	/* Set the DSP frequency */
287	value = spec->freq;
288	if ( ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0 ) {
289		perror("SNDCTL_DSP_SPEED");
290		SDL_SetError("Couldn't set audio frequency");
291		DSP_CloseAudio(this);
292		return(-1);
293	}
294	spec->freq = value;
295
296	/* Calculate the final parameters for this audio specification */
297	SDL_CalculateAudioSpec(spec);
298
299	/* Determine the power of two of the fragment size */
300	for ( frag_spec = 0; (0x01U<<frag_spec) < spec->size; ++frag_spec );
301	if ( (0x01U<<frag_spec) != spec->size ) {
302		SDL_SetError("Fragment size must be a power of two");
303		DSP_CloseAudio(this);
304		return(-1);
305	}
306	frag_spec |= 0x00020000;	/* two fragments, for low latency */
307
308	/* Set the audio buffering parameters */
309#ifdef DEBUG_AUDIO
310	fprintf(stderr, "Requesting %d fragments of size %d\n",
311		(frag_spec >> 16), 1<<(frag_spec&0xFFFF));
312#endif
313	if ( ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0 ) {
314		perror("SNDCTL_DSP_SETFRAGMENT");
315	}
316#ifdef DEBUG_AUDIO
317	{ audio_buf_info info;
318	  ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info);
319	  fprintf(stderr, "fragments = %d\n", info.fragments);
320	  fprintf(stderr, "fragstotal = %d\n", info.fragstotal);
321	  fprintf(stderr, "fragsize = %d\n", info.fragsize);
322	  fprintf(stderr, "bytes = %d\n", info.bytes);
323	}
324#endif
325
326	/* Allocate mixing buffer */
327	mixlen = spec->size;
328	mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen);
329	if ( mixbuf == NULL ) {
330		DSP_CloseAudio(this);
331		return(-1);
332	}
333	SDL_memset(mixbuf, spec->silence, spec->size);
334
335	/* Get the parent process id (we're the parent of the audio thread) */
336	parent = getpid();
337
338	/* We're ready to rock and roll. :-) */
339	return(0);
340}
341