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SDL_ConvertAudio(3)	       SDL API Reference	   SDL_ConvertAudio(3)

NAME
       SDL_ConvertAudio - Convert audio data to a desired audio format.

SYNOPSIS
       #include "SDL.h"

       int SDL_ConvertAudio(SDL_AudioCVT *cvt);

DESCRIPTION
       SDL_ConvertAudio  takes	one  parameter, cvt, which was previously ini-
       tilized. Initilizing a SDL_AudioCVT is a two  step  process.  First  of
       all,  the  structure  must  be  passed  to SDL_BuildAudioCVT along with
       source and destination format parameters. Secondly,  the  cvt->buf  and
       cvt->len  fields must be setup. cvt->buf should point to the audio data
       and cvt->len should be set to the length of the audio  data  in	bytes.
       Remember,  the  length  of  the	buffer	pointed  to  by  buf  show  be
       len*len_mult bytes in length.

       Once the SDL_AudioCVTstructure is initilized then we  can  pass	it  to
       SDL_ConvertAudio,  which  will  convert	the  audio  data pointer to by
       cvt->buf. If SDL_ConvertAudio returned 0 then the conversion  was  com-
       pleted successfully, otherwise -1 is returned.

       If  the conversion completed successfully then the converted audio data
       can be read from cvt->buf. The amount of valid, converted,  audio  data
       in the buffer is equal to cvt->len*cvt->len_ratio.

EXAMPLES
       /* 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=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
       obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));

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

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

       free(desired);

       /* Load the test.wav */
       if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){
	 fprintf(stderr, "Could not open test.wav: %s
       ", SDL_GetError());
	 SDL_CloseAudio();
	 free(obtained);
	 exit(-1);
       }

       /* Build AudioCVT */
       ret = SDL_BuildAudioCVT(&wav_cvt,
			       wav_spec.format, wav_spec.channels, wav_spec.freq,
			       obtained->format, obtained->channels, obtained->freq);

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

       /* Setup for conversion */
       wav_cvt.buf=(Uint8 *)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(&wav_cvt);

       /* do whatever */
       .
       .
       .
       .

SEE ALSO
       SDL_BuildAudioCVT, SDL_AudioCVT

SDL			    Tue 11 Sep 2001, 22:58	   SDL_ConvertAudio(3)