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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 |
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