SDL_ConvertAudio(3)

1SDL_ConvertAudio(3)            SDL API Reference           SDL_ConvertAudio(3)
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NAME

6       SDL_ConvertAudio- Convert audio data to a desired audio format.
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SYNOPSIS

9       #include "SDL.h"
10
11       int SDL_ConvertAudio(SDL_AudioCVT *cvt);
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DESCRIPTION

14       SDL_ConvertAudio  takes  one  parameter, cvt, which was previously ini‐
15       tilized. Initilizing a SDL_AudioCVT is a two  step  process.  First  of
16       all,  the  structure  must  be  passed  to SDL_BuildAudioCVT along with
17       source and destination format parameters. Secondly,  the  cvt->buf  and
18       cvt->len  fields must be setup. cvt->buf should point to the audio data
19       and cvt->len should be set to the length of the audio  data  in  bytes.
20       Remember,  the  length  of  the  buffer  pointed  to  by  buf  show  be
21       len*len_mult bytes in length.
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23       Once the SDL_AudioCVTstructure is initilized then we  can  pass  it  to
24       SDL_ConvertAudio,  which  will  convert  the  audio  data pointer to by
25       cvt->buf. If SDL_ConvertAudio returned 0 then the conversion  was  com‐
26       pleted successfully, otherwise -1 is returned.
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28       If  the conversion completed successfully then the converted audio data
29       can be read from cvt->buf. The amount of valid, converted,  audio  data
30       in the buffer is equal to cvt->len*cvt->len_ratio.
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EXAMPLES

33       /* Converting some WAV data to hardware format */
34       void my_audio_callback(void *userdata, Uint8 *stream, int len);
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36       SDL_AudioSpec *desired, *obtained;
37       SDL_AudioSpec wav_spec;
38       SDL_AudioCVT  wav_cvt;
39       Uint32 wav_len;
40       Uint8 *wav_buf;
41       int ret;
42
43       /* Allocated audio specs */
44       desired=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
45       obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
46
47       /* Set desired format */
48       desired->freq=22050;
49       desired->format=AUDIO_S16LSB;
50       desired->samples=8192;
51       desired->callback=my_audio_callback;
52       desired->userdata=NULL;
53
54       /* Open the audio device */
55       if ( SDL_OpenAudio(desired, obtained) < 0 ){
56         fprintf(stderr, "Couldn't open audio: %s
57       ", SDL_GetError());
58         exit(-1);
59       }
60
61       free(desired);
62
63       /* Load the test.wav */
64       if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){
65         fprintf(stderr, "Could not open test.wav: %s
66       ", SDL_GetError());
67         SDL_CloseAudio();
68         free(obtained);
69         exit(-1);
70       }
71
72       /* Build AudioCVT */
73       ret = SDL_BuildAudioCVT(&wav_cvt,
74                               wav_spec.format, wav_spec.channels, wav_spec.freq,
75                               obtained->format, obtained->channels, obtained->freq);
76
77       /* Check that the convert was built */
78       if(ret==-1){
79         fprintf(stderr, "Couldn't build converter!
80       ");
81         SDL_CloseAudio();
82         free(obtained);
83         SDL_FreeWAV(wav_buf);
84       }
85
86       /* Setup for conversion */
87       wav_cvt.buf=(Uint8 *)malloc(wav_len*wav_cvt.len_mult);
88       wav_cvt.len=wav_len;
89       memcpy(wav_cvt.buf, wav_buf, wav_len);
90
91       /* We can delete to original WAV data now */
92       SDL_FreeWAV(wav_buf);
93
94       /* And now we're ready to convert */
95       SDL_ConvertAudio(&wav_cvt);
96
97       /* do whatever */
98       .
99       .
100       .
101       .
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NAME

SYNOPSIS

DESCRIPTION

EXAMPLES

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