| 1 | <HTML |
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| 4 | >SDL_ConvertAudio</TITLE |
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| 37 | ><TH |
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| 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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| 50 | >Prev</A |
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| 60 | VALIGN="bottom" |
| 61 | ><A |
| 62 | HREF="sdlmixaudio.html" |
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| 68 | ><HR |
| 69 | ALIGN="LEFT" |
| 70 | WIDTH="100%"></DIV |
| 71 | ><H1 |
| 72 | ><A |
| 73 | NAME="SDLCONVERTAUDIO" |
| 74 | ></A |
| 75 | >SDL_ConvertAudio</H1 |
| 76 | ><DIV |
| 77 | CLASS="REFNAMEDIV" |
| 78 | ><A |
| 79 | NAME="AEN7048" |
| 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 |
| 87 | NAME="AEN7051" |
| 88 | ></A |
| 89 | ><H2 |
| 90 | >Synopsis</H2 |
| 91 | ><DIV |
| 92 | CLASS="FUNCSYNOPSIS" |
| 93 | ><A |
| 94 | NAME="AEN7052" |
| 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 |
| 118 | NAME="AEN7058" |
| 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 |
| 246 | NAME="AEN7093" |
| 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 */ |
| 263 | desired = malloc(sizeof(SDL_AudioSpec)); |
| 264 | obtained = malloc(sizeof(SDL_AudioSpec)); |
| 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 */ |
| 303 | wav_cvt.buf = malloc(wav_len * wav_cvt.len_mult); |
| 304 | wav_cvt.len = wav_len; |
| 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 |
| 323 | NAME="AEN7096" |
| 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 |
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| 357 | VALIGN="top" |
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| 387 | >SDL_BuildAudioCVT</TD |
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| 390 | ALIGN="center" |
| 391 | VALIGN="top" |
| 392 | ><A |
| 393 | HREF="audio.html" |
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| 401 | >SDL_MixAudio</TD |
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| 407 | > |