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comparison docs/man3/SDL_ConvertAudio.3 @ 0:74212992fb08

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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
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children 55f1f1b3e27d
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1 .TH "SDL_ConvertAudio" "3" "Mon 12 Mar 2001, 01:02" "SDL" "SDL API Reference"
2 .SH "NAME"
3 SDL_ConvertAudio\- Convert audio data to a desired audio format\&.
4 .SH "SYNOPSIS"
5 .PP
6 \fB#include "SDL\&.h"
7 .sp
8 \fBint \fBSDL_ConvertAudio\fP\fR(\fBSDL_AudioCVT *cvt\fR);
9 .SH "DESCRIPTION"
10 .PP
11 \fBSDL_ConvertAudio\fP takes one parameter, \fBcvt\fR, which was previously initilized\&. Initilizing a \fI\fBSDL_AudioCVT\fR\fR is a two step process\&. First of all, the structure must be passed to \fI\fBSDL_BuildAudioCVT\fP\fR along with source and destination format parameters\&. Secondly, the \fBcvt\fR->\fBbuf\fR and \fBcvt\fR->\fBlen\fR fields must be setup\&. \fBcvt\fR->\fBbuf\fR should point to the audio data and \fBcvt\fR->\fBlen\fR should be set to the length of the audio data in bytes\&. Remember, the length of the buffer pointed to by \fBbuf\fR show be \fBlen\fR*\fBlen_mult\fR bytes in length\&.
12 .PP
13 Once the \fBSDL_AudioCVT\fRstructure is initilized then we can pass it to \fBSDL_ConvertAudio\fP, which will convert the audio data pointer to by \fBcvt\fR->\fBbuf\fR\&. If \fBSDL_ConvertAudio\fP returned \fB0\fR then the conversion was completed successfully, otherwise \fB-1\fR is returned\&.
14 .PP
15 If the conversion completed successfully then the converted audio data can be read from \fBcvt\fR->\fBbuf\fR\&. The amount of valid, converted, audio data in the buffer is equal to \fBcvt\fR->\fBlen\fR*\fBcvt\fR->\fBlen_ratio\fR\&.
16 .SH "EXAMPLES"
17 .PP
18 .nf
19 \f(CW/* Converting some WAV data to hardware format */
20 void my_audio_callback(void *userdata, Uint8 *stream, int len);
21
22 SDL_AudioSpec *desired, *obtained;
23 SDL_AudioSpec wav_spec;
24 SDL_AudioCVT wav_cvt;
25 Uint32 wav_len;
26 Uint8 *wav_buf;
27 int ret;
28
29 /* Allocated audio specs */
30 desired=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
31 obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
32
33 /* Set desired format */
34 desired->freq=22050;
35 desired->format=AUDIO_S16LSB;
36 desired->samples=8192;
37 desired->callback=my_audio_callback;
38 desired->userdata=NULL;
39
40 /* Open the audio device */
41 if ( SDL_OpenAudio(desired, obtained) < 0 ){
42 fprintf(stderr, "Couldn\&'t open audio: %s
43 ", SDL_GetError());
44 exit(-1);
45 }
46
47 free(desired);
48
49 /* Load the test\&.wav */
50 if( SDL_LoadWAV("test\&.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){
51 fprintf(stderr, "Could not open test\&.wav: %s
52 ", SDL_GetError());
53 SDL_CloseAudio();
54 free(obtained);
55 exit(-1);
56 }
57
58 /* Build AudioCVT */
59 ret = SDL_BuildAudioCVT(&wav_cvt,
60 wav_spec\&.format, wav_spec\&.channels, wav_spec\&.freq,
61 obtained->format, obtained->channels, obtained->freq);
62
63 /* Check that the convert was built */
64 if(ret==-1){
65 fprintf(stderr, "Couldn\&'t build converter!
66 ");
67 SDL_CloseAudio();
68 free(obtained);
69 SDL_FreeWAV(wav_buf);
70 }
71
72 /* Setup for conversion */
73 wav_cvt\&.buf=(Uint8 *)malloc(wav_len*wav_cvt\&.len_mult);
74 wav_cvt\&.len=wav_len;
75 memcpy(wav_cvt\&.buf, wav_buf, wav_len);
76
77 /* We can delete to original WAV data now */
78 SDL_FreeWAV(wav_buf);
79
80 /* And now we\&'re ready to convert */
81 SDL_ConvertAudio(&wav_cvt);
82
83 /* do whatever */
84 \&.
85 \&.
86 \&.
87 \&.
88
89 \fR
90 .fi
91 .PP
92 .SH "SEE ALSO"
93 .PP
94 \fI\fBSDL_BuildAudioCVT\fP\fR, \fI\fBSDL_AudioCVT\fP\fR
95 ...\" created by instant / docbook-to-man, Mon 12 Mar 2001, 01:02