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annotate docs/html/sdlconvertaudio.html @ 4159:a1b03ba2fcd0 SDL-1.2
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author | Sam Lantinga <slouken@libsdl.org> |
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date | Mon, 08 Dec 2008 00:25:42 +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 > |