Mercurial > sdl-ios-xcode
annotate 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> |
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date | Fri, 12 Nov 2004 21:39:04 +0000 |
parents | eec28a5278be |
children | c5dedfdb4e42 |
rev | line source |
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0 | 1 /* |
2 SDL - Simple DirectMedia Layer | |
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Updated copyright information for 2004 (Happy New Year!)
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3 Copyright (C) 1997-2004 Sam Lantinga |
0 | 4 |
5 This library is free software; you can redistribute it and/or | |
6 modify it under the terms of the GNU Library General Public | |
7 License as published by the Free Software Foundation; either | |
8 version 2 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 Library General Public License for more details. | |
14 | |
15 You should have received a copy of the GNU Library General Public | |
16 License along with this library; if not, write to the Free | |
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
18 | |
19 Sam Lantinga | |
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20 slouken@libsdl.org |
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21 |
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22 Modified in Oct 2004 by Hannu Savolainen |
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23 hannu@opensound.com |
0 | 24 */ |
25 | |
26 #ifdef SAVE_RCSID | |
27 static char rcsid = | |
28 "@(#) $Id$"; | |
29 #endif | |
30 | |
31 /* Allow access to a raw mixing buffer */ | |
32 | |
33 #include <stdlib.h> | |
34 #include <stdio.h> | |
35 #include <string.h> | |
36 #include <errno.h> | |
37 #include <unistd.h> | |
38 #include <fcntl.h> | |
39 #include <signal.h> | |
40 #include <sys/time.h> | |
41 #include <sys/ioctl.h> | |
42 #include <sys/stat.h> | |
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43 #ifdef OSS_USE_SOUNDCARD_H |
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44 /* This is installed on some systems */ |
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45 #include <soundcard.h> |
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46 #else |
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47 /* This is recommended by OSS */ |
0 | 48 #include <sys/soundcard.h> |
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49 #endif |
0 | 50 |
51 #include "SDL_audio.h" | |
52 #include "SDL_error.h" | |
53 #include "SDL_audiomem.h" | |
54 #include "SDL_audio_c.h" | |
55 #include "SDL_timer.h" | |
56 #include "SDL_audiodev_c.h" | |
57 #include "SDL_dspaudio.h" | |
58 | |
59 /* The tag name used by DSP audio */ | |
60 #define DSP_DRIVER_NAME "dsp" | |
61 | |
62 /* Open the audio device for playback, and don't block if busy */ | |
63 #define OPEN_FLAGS (O_WRONLY|O_NONBLOCK) | |
64 | |
65 /* Audio driver functions */ | |
66 static int DSP_OpenAudio(_THIS, SDL_AudioSpec *spec); | |
67 static void DSP_WaitAudio(_THIS); | |
68 static void DSP_PlayAudio(_THIS); | |
69 static Uint8 *DSP_GetAudioBuf(_THIS); | |
70 static void DSP_CloseAudio(_THIS); | |
71 | |
72 /* Audio driver bootstrap functions */ | |
73 | |
74 static int Audio_Available(void) | |
75 { | |
76 int fd; | |
77 int available; | |
78 | |
79 available = 0; | |
80 fd = SDL_OpenAudioPath(NULL, 0, OPEN_FLAGS, 0); | |
81 if ( fd >= 0 ) { | |
82 available = 1; | |
83 close(fd); | |
84 } | |
85 return(available); | |
86 } | |
87 | |
88 static void Audio_DeleteDevice(SDL_AudioDevice *device) | |
89 { | |
90 free(device->hidden); | |
91 free(device); | |
92 } | |
93 | |
94 static SDL_AudioDevice *Audio_CreateDevice(int devindex) | |
95 { | |
96 SDL_AudioDevice *this; | |
97 | |
98 /* Initialize all variables that we clean on shutdown */ | |
99 this = (SDL_AudioDevice *)malloc(sizeof(SDL_AudioDevice)); | |
100 if ( this ) { | |
101 memset(this, 0, (sizeof *this)); | |
102 this->hidden = (struct SDL_PrivateAudioData *) | |
103 malloc((sizeof *this->hidden)); | |
104 } | |
105 if ( (this == NULL) || (this->hidden == NULL) ) { | |
106 SDL_OutOfMemory(); | |
107 if ( this ) { | |
108 free(this); | |
109 } | |
110 return(0); | |
111 } | |
112 memset(this->hidden, 0, (sizeof *this->hidden)); | |
113 audio_fd = -1; | |
114 | |
115 /* Set the function pointers */ | |
116 this->OpenAudio = DSP_OpenAudio; | |
117 this->WaitAudio = DSP_WaitAudio; | |
118 this->PlayAudio = DSP_PlayAudio; | |
119 this->GetAudioBuf = DSP_GetAudioBuf; | |
120 this->CloseAudio = DSP_CloseAudio; | |
121 | |
122 this->free = Audio_DeleteDevice; | |
123 | |
124 return this; | |
125 } | |
126 | |
127 AudioBootStrap DSP_bootstrap = { | |
128 DSP_DRIVER_NAME, "OSS /dev/dsp standard audio", | |
129 Audio_Available, Audio_CreateDevice | |
130 }; | |
131 | |
132 /* This function waits until it is possible to write a full sound buffer */ | |
133 static void DSP_WaitAudio(_THIS) | |
134 { | |
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135 /* Not needed at all since OSS handles waiting automagically */ |
0 | 136 } |
137 | |
138 static void DSP_PlayAudio(_THIS) | |
139 { | |
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140 if (write(audio_fd, mixbuf, mixlen)==-1) |
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141 { |
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142 perror("Audio write"); |
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143 this->enabled = 0; |
0 | 144 } |
145 | |
146 #ifdef DEBUG_AUDIO | |
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147 fprintf(stderr, "Wrote %d bytes of audio data\n", mixlen); |
0 | 148 #endif |
149 } | |
150 | |
151 static Uint8 *DSP_GetAudioBuf(_THIS) | |
152 { | |
153 return(mixbuf); | |
154 } | |
155 | |
156 static void DSP_CloseAudio(_THIS) | |
157 { | |
158 if ( mixbuf != NULL ) { | |
159 SDL_FreeAudioMem(mixbuf); | |
160 mixbuf = NULL; | |
161 } | |
162 if ( audio_fd >= 0 ) { | |
163 close(audio_fd); | |
164 audio_fd = -1; | |
165 } | |
166 } | |
167 | |
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168 static int DSP_OpenAudio(_THIS, SDL_AudioSpec *spec) |
0 | 169 { |
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170 char audiodev[1024]; |
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171 int format; |
0 | 172 int value; |
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173 int frag_spec; |
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174 Uint16 test_format; |
0 | 175 |
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176 /* Open the audio device */ |
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177 audio_fd = SDL_OpenAudioPath(audiodev, sizeof(audiodev), OPEN_FLAGS, 0); |
0 | 178 if ( audio_fd < 0 ) { |
179 SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno)); | |
180 return(-1); | |
181 } | |
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182 mixbuf = NULL; |
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183 |
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184 /* Make the file descriptor use blocking writes with fcntl() */ |
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185 { long flags; |
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186 flags = fcntl(audio_fd, F_GETFL); |
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187 flags &= ~O_NONBLOCK; |
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188 if ( fcntl(audio_fd, F_SETFL, flags) < 0 ) { |
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189 SDL_SetError("Couldn't set audio blocking mode"); |
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190 return(-1); |
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191 } |
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192 } |
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193 |
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194 /* Get a list of supported hardware formats */ |
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195 if ( ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0 ) { |
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196 perror("SNDCTL_DSP_GETFMTS"); |
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197 SDL_SetError("Couldn't get audio format list"); |
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198 return(-1); |
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199 } |
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200 |
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201 /* Try for a closest match on audio format */ |
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202 format = 0; |
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203 for ( test_format = SDL_FirstAudioFormat(spec->format); |
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204 ! format && test_format; ) { |
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205 #ifdef DEBUG_AUDIO |
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206 fprintf(stderr, "Trying format 0x%4.4x\n", test_format); |
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207 #endif |
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208 switch ( test_format ) { |
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209 case AUDIO_U8: |
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210 if ( value & AFMT_U8 ) { |
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211 format = AFMT_U8; |
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212 } |
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213 break; |
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214 case AUDIO_S16LSB: |
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215 if ( value & AFMT_S16_LE ) { |
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216 format = AFMT_S16_LE; |
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217 } |
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218 break; |
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219 case AUDIO_S16MSB: |
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220 if ( value & AFMT_S16_BE ) { |
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221 format = AFMT_S16_BE; |
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222 } |
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223 break; |
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224 #if 0 |
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225 /* |
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226 * These formats are not used by any real life systems so they are not |
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227 * needed here. |
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228 */ |
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229 case AUDIO_S8: |
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230 if ( value & AFMT_S8 ) { |
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231 format = AFMT_S8; |
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232 } |
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233 break; |
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234 case AUDIO_U16LSB: |
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235 if ( value & AFMT_U16_LE ) { |
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236 format = AFMT_U16_LE; |
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237 } |
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238 break; |
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239 case AUDIO_U16MSB: |
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240 if ( value & AFMT_U16_BE ) { |
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241 format = AFMT_U16_BE; |
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242 } |
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243 break; |
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244 #endif |
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245 default: |
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246 format = 0; |
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247 break; |
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248 } |
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249 if ( ! format ) { |
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250 test_format = SDL_NextAudioFormat(); |
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251 } |
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252 } |
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253 if ( format == 0 ) { |
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254 SDL_SetError("Couldn't find any hardware audio formats"); |
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255 return(-1); |
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256 } |
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257 spec->format = test_format; |
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258 |
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259 /* Set the audio format */ |
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260 value = format; |
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261 if ( (ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) || |
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262 (value != format) ) { |
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263 perror("SNDCTL_DSP_SETFMT"); |
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264 SDL_SetError("Couldn't set audio format"); |
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265 return(-1); |
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266 } |
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267 |
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268 /* Set the number of channels of output */ |
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269 value = spec->channels; |
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270 if ( ioctl(audio_fd, SNDCTL_DSP_CHANNELS, &value) < 0 ) { |
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271 perror("SNDCTL_DSP_CHANNELS"); |
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272 SDL_SetError("Cannot set the number of channels"); |
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273 return(-1); |
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274 } |
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275 spec->channels = value; |
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276 |
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277 /* Set the DSP frequency */ |
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278 value = spec->freq; |
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279 if ( ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0 ) { |
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280 perror("SNDCTL_DSP_SPEED"); |
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281 SDL_SetError("Couldn't set audio frequency"); |
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282 return(-1); |
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283 } |
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284 spec->freq = value; |
0 | 285 |
286 /* Calculate the final parameters for this audio specification */ | |
287 SDL_CalculateAudioSpec(spec); | |
288 | |
289 /* Determine the power of two of the fragment size */ | |
290 for ( frag_spec = 0; (0x01<<frag_spec) < spec->size; ++frag_spec ); | |
291 if ( (0x01<<frag_spec) != spec->size ) { | |
292 SDL_SetError("Fragment size must be a power of two"); | |
293 return(-1); | |
294 } | |
295 frag_spec |= 0x00020000; /* two fragments, for low latency */ | |
296 | |
297 /* Set the audio buffering parameters */ | |
298 #ifdef DEBUG_AUDIO | |
299 fprintf(stderr, "Requesting %d fragments of size %d\n", | |
300 (frag_spec >> 16), 1<<(frag_spec&0xFFFF)); | |
301 #endif | |
302 if ( ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0 ) { | |
968
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303 perror("SNDCTL_DSP_SETFRAGMENT"); |
0 | 304 fprintf(stderr, "Warning: Couldn't set audio fragment size\n"); |
305 } | |
306 #ifdef DEBUG_AUDIO | |
307 { audio_buf_info info; | |
308 ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info); | |
309 fprintf(stderr, "fragments = %d\n", info.fragments); | |
310 fprintf(stderr, "fragstotal = %d\n", info.fragstotal); | |
311 fprintf(stderr, "fragsize = %d\n", info.fragsize); | |
312 fprintf(stderr, "bytes = %d\n", info.bytes); | |
313 } | |
314 #endif | |
315 | |
316 /* Allocate mixing buffer */ | |
317 mixlen = spec->size; | |
318 mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen); | |
319 if ( mixbuf == NULL ) { | |
320 return(-1); | |
321 } | |
322 memset(mixbuf, spec->silence, spec->size); | |
323 | |
324 /* Get the parent process id (we're the parent of the audio thread) */ | |
325 parent = getpid(); | |
326 | |
327 /* We're ready to rock and roll. :-) */ | |
328 return(0); | |
329 } |