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annotate docs/html/sdlconvertaudio.html @ 2846:3d7833d5a4be
Slight optimization of the shader, no need to scale into 0..255
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 07 Dec 2008 04:38:32 +0000 |
| parents | 355632dca928 |
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| rev | line source |
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| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_ConvertAudio</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ |
| 0 | 8 "><LINK |
| 9 REL="HOME" | |
| 10 TITLE="SDL Library Documentation" | |
| 11 HREF="index.html"><LINK | |
| 12 REL="UP" | |
| 13 TITLE="Audio" | |
| 14 HREF="audio.html"><LINK | |
| 15 REL="PREVIOUS" | |
| 16 TITLE="SDL_BuildAudioCVT" | |
| 17 HREF="sdlbuildaudiocvt.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_MixAudio" | |
| 20 HREF="sdlmixaudio.html"></HEAD | |
| 21 ><BODY | |
| 22 CLASS="REFENTRY" | |
| 23 BGCOLOR="#FFF8DC" | |
| 24 TEXT="#000000" | |
| 25 LINK="#0000ee" | |
| 26 VLINK="#551a8b" | |
| 27 ALINK="#ff0000" | |
| 28 ><DIV | |
| 29 CLASS="NAVHEADER" | |
| 30 ><TABLE | |
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31 SUMMARY="Header navigation table" |
| 0 | 32 WIDTH="100%" |
| 33 BORDER="0" | |
| 34 CELLPADDING="0" | |
| 35 CELLSPACING="0" | |
| 36 ><TR | |
| 37 ><TH | |
| 38 COLSPAN="3" | |
| 39 ALIGN="center" | |
| 40 >SDL Library Documentation</TH | |
| 41 ></TR | |
| 42 ><TR | |
| 43 ><TD | |
| 44 WIDTH="10%" | |
| 45 ALIGN="left" | |
| 46 VALIGN="bottom" | |
| 47 ><A | |
| 48 HREF="sdlbuildaudiocvt.html" | |
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49 ACCESSKEY="P" |
| 0 | 50 >Prev</A |
| 51 ></TD | |
| 52 ><TD | |
| 53 WIDTH="80%" | |
| 54 ALIGN="center" | |
| 55 VALIGN="bottom" | |
| 56 ></TD | |
| 57 ><TD | |
| 58 WIDTH="10%" | |
| 59 ALIGN="right" | |
| 60 VALIGN="bottom" | |
| 61 ><A | |
| 62 HREF="sdlmixaudio.html" | |
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63 ACCESSKEY="N" |
| 0 | 64 >Next</A |
| 65 ></TD | |
| 66 ></TR | |
| 67 ></TABLE | |
| 68 ><HR | |
| 69 ALIGN="LEFT" | |
| 70 WIDTH="100%"></DIV | |
| 71 ><H1 | |
| 72 ><A | |
| 73 NAME="SDLCONVERTAUDIO" | |
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74 ></A |
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75 >SDL_ConvertAudio</H1 |
| 0 | 76 ><DIV |
| 77 CLASS="REFNAMEDIV" | |
| 78 ><A | |
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79 NAME="AEN7048" |
| 0 | 80 ></A |
| 81 ><H2 | |
| 82 >Name</H2 | |
| 83 >SDL_ConvertAudio -- Convert audio data to a desired audio format.</DIV | |
| 84 ><DIV | |
| 85 CLASS="REFSYNOPSISDIV" | |
| 86 ><A | |
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87 NAME="AEN7051" |
| 0 | 88 ></A |
| 89 ><H2 | |
| 90 >Synopsis</H2 | |
| 91 ><DIV | |
| 92 CLASS="FUNCSYNOPSIS" | |
| 93 ><A | |
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94 NAME="AEN7052" |
| 0 | 95 ></A |
| 96 ><P | |
| 97 ></P | |
| 98 ><PRE | |
| 99 CLASS="FUNCSYNOPSISINFO" | |
| 100 >#include "SDL.h"</PRE | |
| 101 ><P | |
| 102 ><CODE | |
| 103 ><CODE | |
| 104 CLASS="FUNCDEF" | |
| 105 >int <B | |
| 106 CLASS="FSFUNC" | |
| 107 >SDL_ConvertAudio</B | |
| 108 ></CODE | |
| 109 >(SDL_AudioCVT *cvt);</CODE | |
| 110 ></P | |
| 111 ><P | |
| 112 ></P | |
| 113 ></DIV | |
| 114 ></DIV | |
| 115 ><DIV | |
| 116 CLASS="REFSECT1" | |
| 117 ><A | |
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118 NAME="AEN7058" |
| 0 | 119 ></A |
| 120 ><H2 | |
| 121 >Description</H2 | |
| 122 ><P | |
| 123 ><TT | |
| 124 CLASS="FUNCTION" | |
| 125 >SDL_ConvertAudio</TT | |
| 126 > takes one parameter, <TT | |
| 127 CLASS="PARAMETER" | |
| 128 ><I | |
| 129 >cvt</I | |
| 130 ></TT | |
| 131 >, which was previously initilized. Initilizing a <A | |
| 132 HREF="sdlaudiocvt.html" | |
| 133 ><SPAN | |
| 134 CLASS="STRUCTNAME" | |
| 135 >SDL_AudioCVT</SPAN | |
| 136 ></A | |
| 137 > is a two step process. First of all, the structure must be passed to <A | |
| 138 HREF="sdlbuildaudiocvt.html" | |
| 139 ><TT | |
| 140 CLASS="FUNCTION" | |
| 141 >SDL_BuildAudioCVT</TT | |
| 142 ></A | |
| 143 > along with source and destination format parameters. Secondly, the <SPAN | |
| 144 CLASS="STRUCTNAME" | |
| 145 >cvt</SPAN | |
| 146 >-><TT | |
| 147 CLASS="STRUCTFIELD" | |
| 148 ><I | |
| 149 >buf</I | |
| 150 ></TT | |
| 151 > and <SPAN | |
| 152 CLASS="STRUCTNAME" | |
| 153 >cvt</SPAN | |
| 154 >-><TT | |
| 155 CLASS="STRUCTFIELD" | |
| 156 ><I | |
| 157 >len</I | |
| 158 ></TT | |
| 159 > fields must be setup. <SPAN | |
| 160 CLASS="STRUCTNAME" | |
| 161 >cvt</SPAN | |
| 162 >-><TT | |
| 163 CLASS="STRUCTFIELD" | |
| 164 ><I | |
| 165 >buf</I | |
| 166 ></TT | |
| 167 > should point to the audio data and <SPAN | |
| 168 CLASS="STRUCTNAME" | |
| 169 >cvt</SPAN | |
| 170 >-><TT | |
| 171 CLASS="STRUCTFIELD" | |
| 172 ><I | |
| 173 >len</I | |
| 174 ></TT | |
| 175 > should be set to the length of the audio data in bytes. Remember, the length of the buffer pointed to by <TT | |
| 176 CLASS="STRUCTFIELD" | |
| 177 ><I | |
| 178 >buf</I | |
| 179 ></TT | |
| 180 > show be <TT | |
| 181 CLASS="STRUCTFIELD" | |
| 182 ><I | |
| 183 >len</I | |
| 184 ></TT | |
| 185 >*<TT | |
| 186 CLASS="STRUCTFIELD" | |
| 187 ><I | |
| 188 >len_mult</I | |
| 189 ></TT | |
| 190 > bytes in length.</P | |
| 191 ><P | |
| 192 >Once the <SPAN | |
| 193 CLASS="STRUCTNAME" | |
| 194 >SDL_AudioCVT</SPAN | |
| 195 >structure is initilized then we can pass it to <TT | |
| 196 CLASS="FUNCTION" | |
| 197 >SDL_ConvertAudio</TT | |
| 198 >, which will convert the audio data pointer to by <SPAN | |
| 199 CLASS="STRUCTNAME" | |
| 200 >cvt</SPAN | |
| 201 >-><TT | |
| 202 CLASS="STRUCTFIELD" | |
| 203 ><I | |
| 204 >buf</I | |
| 205 ></TT | |
| 206 >. If <TT | |
| 207 CLASS="FUNCTION" | |
| 208 >SDL_ConvertAudio</TT | |
| 209 > returned <SPAN | |
| 210 CLASS="RETURNVALUE" | |
| 211 >0</SPAN | |
| 212 > then the conversion was completed successfully, otherwise <SPAN | |
| 213 CLASS="RETURNVALUE" | |
| 214 >-1</SPAN | |
| 215 > is returned.</P | |
| 216 ><P | |
| 217 >If the conversion completed successfully then the converted audio data can be read from <SPAN | |
| 218 CLASS="STRUCTNAME" | |
| 219 >cvt</SPAN | |
| 220 >-><TT | |
| 221 CLASS="STRUCTFIELD" | |
| 222 ><I | |
| 223 >buf</I | |
| 224 ></TT | |
| 225 >. The amount of valid, converted, audio data in the buffer is equal to <SPAN | |
| 226 CLASS="STRUCTNAME" | |
| 227 >cvt</SPAN | |
| 228 >-><TT | |
| 229 CLASS="STRUCTFIELD" | |
| 230 ><I | |
| 231 >len</I | |
| 232 ></TT | |
| 233 >*<TT | |
| 234 CLASS="STRUCTFIELD" | |
| 235 ><I | |
| 236 >cvt</I | |
| 237 ></TT | |
| 238 >-><SPAN | |
| 239 CLASS="STRUCTNAME" | |
| 240 >len_ratio</SPAN | |
| 241 >.</P | |
| 242 ></DIV | |
| 243 ><DIV | |
| 244 CLASS="REFSECT1" | |
| 245 ><A | |
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246 NAME="AEN7093" |
| 0 | 247 ></A |
| 248 ><H2 | |
| 249 >Examples</H2 | |
| 250 ><PRE | |
| 251 CLASS="PROGRAMLISTING" | |
| 252 >/* Converting some WAV data to hardware format */ | |
| 253 void my_audio_callback(void *userdata, Uint8 *stream, int len); | |
| 254 | |
| 255 SDL_AudioSpec *desired, *obtained; | |
| 256 SDL_AudioSpec wav_spec; | |
| 257 SDL_AudioCVT wav_cvt; | |
| 258 Uint32 wav_len; | |
| 259 Uint8 *wav_buf; | |
| 260 int ret; | |
| 261 | |
| 262 /* Allocated audio specs */ | |
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263 desired = malloc(sizeof(SDL_AudioSpec)); |
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264 obtained = malloc(sizeof(SDL_AudioSpec)); |
| 0 | 265 |
| 266 /* Set desired format */ | |
| 267 desired->freq=22050; | |
| 268 desired->format=AUDIO_S16LSB; | |
| 269 desired->samples=8192; | |
| 270 desired->callback=my_audio_callback; | |
| 271 desired->userdata=NULL; | |
| 272 | |
| 273 /* Open the audio device */ | |
| 274 if ( SDL_OpenAudio(desired, obtained) < 0 ){ | |
| 275 fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError()); | |
| 276 exit(-1); | |
| 277 } | |
| 278 | |
| 279 free(desired); | |
| 280 | |
| 281 /* Load the test.wav */ | |
| 282 if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){ | |
| 283 fprintf(stderr, "Could not open test.wav: %s\n", SDL_GetError()); | |
| 284 SDL_CloseAudio(); | |
| 285 free(obtained); | |
| 286 exit(-1); | |
| 287 } | |
| 288 | |
| 289 /* Build AudioCVT */ | |
| 290 ret = SDL_BuildAudioCVT(&wav_cvt, | |
| 291 wav_spec.format, wav_spec.channels, wav_spec.freq, | |
| 292 obtained->format, obtained->channels, obtained->freq); | |
| 293 | |
| 294 /* Check that the convert was built */ | |
| 295 if(ret==-1){ | |
| 296 fprintf(stderr, "Couldn't build converter!\n"); | |
| 297 SDL_CloseAudio(); | |
| 298 free(obtained); | |
| 299 SDL_FreeWAV(wav_buf); | |
| 300 } | |
| 301 | |
| 302 /* Setup for conversion */ | |
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303 wav_cvt.buf = malloc(wav_len * wav_cvt.len_mult); |
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304 wav_cvt.len = wav_len; |
| 0 | 305 memcpy(wav_cvt.buf, wav_buf, wav_len); |
| 306 | |
| 307 /* We can delete to original WAV data now */ | |
| 308 SDL_FreeWAV(wav_buf); | |
| 309 | |
| 310 /* And now we're ready to convert */ | |
| 311 SDL_ConvertAudio(&wav_cvt); | |
| 312 | |
| 313 /* do whatever */ | |
| 314 . | |
| 315 . | |
| 316 . | |
| 317 . | |
| 318 </PRE | |
| 319 ></DIV | |
| 320 ><DIV | |
| 321 CLASS="REFSECT1" | |
| 322 ><A | |
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323 NAME="AEN7096" |
| 0 | 324 ></A |
| 325 ><H2 | |
| 326 >See Also</H2 | |
| 327 ><P | |
| 328 ><A | |
| 329 HREF="sdlbuildaudiocvt.html" | |
| 330 ><TT | |
| 331 CLASS="FUNCTION" | |
| 332 >SDL_BuildAudioCVT</TT | |
| 333 ></A | |
| 334 >, | |
| 335 <A | |
| 336 HREF="sdlaudiocvt.html" | |
| 337 ><TT | |
| 338 CLASS="FUNCTION" | |
| 339 >SDL_AudioCVT</TT | |
| 340 ></A | |
| 341 ></P | |
| 342 ></DIV | |
| 343 ><DIV | |
| 344 CLASS="NAVFOOTER" | |
| 345 ><HR | |
| 346 ALIGN="LEFT" | |
| 347 WIDTH="100%"><TABLE | |
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348 SUMMARY="Footer navigation table" |
| 0 | 349 WIDTH="100%" |
| 350 BORDER="0" | |
| 351 CELLPADDING="0" | |
| 352 CELLSPACING="0" | |
| 353 ><TR | |
| 354 ><TD | |
| 355 WIDTH="33%" | |
| 356 ALIGN="left" | |
| 357 VALIGN="top" | |
| 358 ><A | |
| 359 HREF="sdlbuildaudiocvt.html" | |
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360 ACCESSKEY="P" |
| 0 | 361 >Prev</A |
| 362 ></TD | |
| 363 ><TD | |
| 364 WIDTH="34%" | |
| 365 ALIGN="center" | |
| 366 VALIGN="top" | |
| 367 ><A | |
| 368 HREF="index.html" | |
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369 ACCESSKEY="H" |
| 0 | 370 >Home</A |
| 371 ></TD | |
| 372 ><TD | |
| 373 WIDTH="33%" | |
| 374 ALIGN="right" | |
| 375 VALIGN="top" | |
| 376 ><A | |
| 377 HREF="sdlmixaudio.html" | |
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378 ACCESSKEY="N" |
| 0 | 379 >Next</A |
| 380 ></TD | |
| 381 ></TR | |
| 382 ><TR | |
| 383 ><TD | |
| 384 WIDTH="33%" | |
| 385 ALIGN="left" | |
| 386 VALIGN="top" | |
| 387 >SDL_BuildAudioCVT</TD | |
| 388 ><TD | |
| 389 WIDTH="34%" | |
| 390 ALIGN="center" | |
| 391 VALIGN="top" | |
| 392 ><A | |
| 393 HREF="audio.html" | |
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394 ACCESSKEY="U" |
| 0 | 395 >Up</A |
| 396 ></TD | |
| 397 ><TD | |
| 398 WIDTH="33%" | |
| 399 ALIGN="right" | |
| 400 VALIGN="top" | |
| 401 >SDL_MixAudio</TD | |
| 402 ></TR | |
| 403 ></TABLE | |
| 404 ></DIV | |
| 405 ></BODY | |
| 406 ></HTML | |
| 407 > |