[sdl_omap.git] / docs / html / sdlconvertaudio.html

<HTML
><HEAD
><TITLE
>SDL_ConvertAudio</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Audio"
HREF="audio.html"><LINK
REL="PREVIOUS"
TITLE="SDL_BuildAudioCVT"
HREF="sdlbuildaudiocvt.html"><LINK
REL="NEXT"
TITLE="SDL_MixAudio"
HREF="sdlmixaudio.html"></HEAD
><BODY
CLASS="REFENTRY"
BGCOLOR="#FFF8DC"
TEXT="#000000"
LINK="#0000ee"
VLINK="#551a8b"
ALINK="#ff0000"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>SDL Library Documentation</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="sdlbuildaudiocvt.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="sdlmixaudio.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><H1
><A
NAME="SDLCONVERTAUDIO"
></A
>SDL_ConvertAudio</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN7048"
></A
><H2
>Name</H2
>SDL_ConvertAudio&nbsp;--&nbsp;Convert audio data to a desired audio format.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN7051"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN7052"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_ConvertAudio</B
></CODE
>(SDL_AudioCVT *cvt);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7058"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
> takes one parameter, <TT
CLASS="PARAMETER"
><I
>cvt</I
></TT
>, which was previously initilized. Initilizing a <A
HREF="sdlaudiocvt.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
></A
> is a two step process. First of all, the structure must be passed to <A
HREF="sdlbuildaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_BuildAudioCVT</TT
></A
> along with source and destination format parameters. Secondly, the <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> and <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
> fields must be setup. <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> should point to the audio data and <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
> should be set to the length of the audio data in bytes. Remember, the length of the buffer pointed to by <TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> show be <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
> bytes in length.</P
><P
>Once the <SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
>structure is initilized then we can pass it to <TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
>, which will convert the audio data pointer to by <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
>. If <TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
> returned <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> then the conversion was completed successfully, otherwise <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> is returned.</P
><P
>If the conversion completed successfully then the converted audio data can be read from <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
>. The amount of valid, converted, audio data in the buffer is equal to <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>cvt</I
></TT
>-&#62;<SPAN
CLASS="STRUCTNAME"
>len_ratio</SPAN
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7093"
></A
><H2
>Examples</H2
><PRE
CLASS="PROGRAMLISTING"
>/* Converting some WAV data to hardware format */
void my_audio_callback(void *userdata, Uint8 *stream, int len);

SDL_AudioSpec *desired, *obtained;
SDL_AudioSpec wav_spec;
SDL_AudioCVT  wav_cvt;
Uint32 wav_len;
Uint8 *wav_buf;
int ret;

/* Allocated audio specs */
desired = malloc(sizeof(SDL_AudioSpec));
obtained = malloc(sizeof(SDL_AudioSpec));

/* Set desired format */
desired-&#62;freq=22050;
desired-&#62;format=AUDIO_S16LSB;
desired-&#62;samples=8192;
desired-&#62;callback=my_audio_callback;
desired-&#62;userdata=NULL;

/* Open the audio device */
if ( SDL_OpenAudio(desired, obtained) &#60; 0 ){
  fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
  exit(-1);
}
        
free(desired);

/* Load the test.wav */
if( SDL_LoadWAV("test.wav", &#38;wav_spec, &#38;wav_buf, &#38;wav_len) == NULL ){
  fprintf(stderr, "Could not open test.wav: %s\n", SDL_GetError());
  SDL_CloseAudio();
  free(obtained);
  exit(-1);
}
                                            
/* Build AudioCVT */
ret = SDL_BuildAudioCVT(&#38;wav_cvt,
                        wav_spec.format, wav_spec.channels, wav_spec.freq,
                        obtained-&#62;format, obtained-&#62;channels, obtained-&#62;freq);

/* Check that the convert was built */
if(ret==-1){
  fprintf(stderr, "Couldn't build converter!\n");
  SDL_CloseAudio();
  free(obtained);
  SDL_FreeWAV(wav_buf);
}

/* Setup for conversion */
wav_cvt.buf = malloc(wav_len * wav_cvt.len_mult);
wav_cvt.len = wav_len;
memcpy(wav_cvt.buf, wav_buf, wav_len);

/* We can delete to original WAV data now */
SDL_FreeWAV(wav_buf);

/* And now we're ready to convert */
SDL_ConvertAudio(&#38;wav_cvt);

/* do whatever */
.
.
.
.
&#13;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7096"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlbuildaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_BuildAudioCVT</TT
></A
>,
<A
HREF="sdlaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_AudioCVT</TT
></A
></P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="sdlbuildaudiocvt.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="sdlmixaudio.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>SDL_BuildAudioCVT</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="audio.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>SDL_MixAudio</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
Commit	Line	Data
e14743d1	1	<HTML
	2	><HEAD
	3	><TITLE
	4	>SDL_ConvertAudio</TITLE
	5	><META
	6	NAME="GENERATOR"
	7	CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
	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
	31	SUMMARY="Header navigation table"
	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"
	49	ACCESSKEY="P"
	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"
	63	ACCESSKEY="N"
	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"
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
343	><DIV
344	CLASS="NAVFOOTER"
345	><HR
346	ALIGN="LEFT"
347	WIDTH="100%"><TABLE
348	SUMMARY="Footer navigation table"
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"
360	ACCESSKEY="P"
361	>Prev</A
362	></TD
363	><TD
364	WIDTH="34%"
365	ALIGN="center"
366	VALIGN="top"
367	><A
368	HREF="index.html"
369	ACCESSKEY="H"
370	>Home</A
371	></TD
372	><TD
373	WIDTH="33%"
374	ALIGN="right"
375	VALIGN="top"
376	><A
377	HREF="sdlmixaudio.html"
378	ACCESSKEY="N"
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"
394	ACCESSKEY="U"
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	>