---
name: "SDL_ConvertAudio"
section: "3"
platform: "linux"
package: "libsdl1.2-dev"
version: "1.2.15+dfsg2-8"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/SDL_ConvertAudio"
---

# SDL\_ConvertAudio(3)

Convert audio data to a desired audio format.

## 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 initilized. 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\_AudioCVT**structure 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 completed 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**