docs/man3/SDL_ConvertAudio.3
author Aaron Wishnick <schnarf@gmail.com>
Wed, 18 Jun 2008 04:51:10 +0000
branchgsoc2008_audio_resampling
changeset 2655 b8e736c8a5a8
parent 2283 546f7c1eb755
child 4311 1238da4a7112
permissions -rw-r--r--
Added beginnings of resampling code.
     1 .TH "SDL_ConvertAudio" "3" "Tue 11 Sep 2001, 22:58" "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, Tue 11 Sep 2001, 22:58