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1 .TH "SDL_ConvertAudio" "3" "Mon 12 Mar 2001, 01:02" "SDL" "SDL API Reference"
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2 .SH "NAME"
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3 SDL_ConvertAudio\- Convert audio data to a desired audio format\&.
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4 .SH "SYNOPSIS"
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5 .PP
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6 \fB#include "SDL\&.h"
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7 .sp
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8 \fBint \fBSDL_ConvertAudio\fP\fR(\fBSDL_AudioCVT *cvt\fR);
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9 .SH "DESCRIPTION"
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10 .PP
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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\&.
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12 .PP
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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\&.
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14 .PP
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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\&.
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16 .SH "EXAMPLES"
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17 .PP
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18 .nf
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19 \f(CW/* Converting some WAV data to hardware format */
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20 void my_audio_callback(void *userdata, Uint8 *stream, int len);
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21
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22 SDL_AudioSpec *desired, *obtained;
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23 SDL_AudioSpec wav_spec;
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24 SDL_AudioCVT wav_cvt;
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25 Uint32 wav_len;
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26 Uint8 *wav_buf;
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27 int ret;
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28
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29 /* Allocated audio specs */
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30 desired=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
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31 obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
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32
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33 /* Set desired format */
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34 desired->freq=22050;
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35 desired->format=AUDIO_S16LSB;
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36 desired->samples=8192;
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37 desired->callback=my_audio_callback;
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38 desired->userdata=NULL;
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39
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40 /* Open the audio device */
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41 if ( SDL_OpenAudio(desired, obtained) < 0 ){
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42 fprintf(stderr, "Couldn\&'t open audio: %s
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43 ", SDL_GetError());
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44 exit(-1);
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45 }
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46
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47 free(desired);
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48
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49 /* Load the test\&.wav */
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50 if( SDL_LoadWAV("test\&.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){
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51 fprintf(stderr, "Could not open test\&.wav: %s
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52 ", SDL_GetError());
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53 SDL_CloseAudio();
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54 free(obtained);
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55 exit(-1);
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56 }
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57
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58 /* Build AudioCVT */
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59 ret = SDL_BuildAudioCVT(&wav_cvt,
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60 wav_spec\&.format, wav_spec\&.channels, wav_spec\&.freq,
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61 obtained->format, obtained->channels, obtained->freq);
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62
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63 /* Check that the convert was built */
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64 if(ret==-1){
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65 fprintf(stderr, "Couldn\&'t build converter!
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66 ");
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67 SDL_CloseAudio();
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68 free(obtained);
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69 SDL_FreeWAV(wav_buf);
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70 }
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71
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72 /* Setup for conversion */
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73 wav_cvt\&.buf=(Uint8 *)malloc(wav_len*wav_cvt\&.len_mult);
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74 wav_cvt\&.len=wav_len;
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75 memcpy(wav_cvt\&.buf, wav_buf, wav_len);
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76
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77 /* We can delete to original WAV data now */
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78 SDL_FreeWAV(wav_buf);
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79
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80 /* And now we\&'re ready to convert */
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81 SDL_ConvertAudio(&wav_cvt);
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82
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83 /* do whatever */
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84 \&.
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85 \&.
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86 \&.
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87 \&.
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88
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89 \fR
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90 .fi
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91 .PP
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92 .SH "SEE ALSO"
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93 .PP
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94 \fI\fBSDL_BuildAudioCVT\fP\fR, \fI\fBSDL_AudioCVT\fP\fR
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95 ...\" created by instant / docbook-to-man, Mon 12 Mar 2001, 01:02
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