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(This is the legacy documentation for stable SDL2, the current stable version; SDL3 is the current development version.)


Convert audio data to a desired audio format.


int SDL_ConvertAudio(SDL_AudioCVT * cvt);

Function Parameters

cvt an SDL_AudioCVT structure that was previously set up by SDL_BuildAudioCVT().

Return Value

Returns 0 if the conversion was completed successfully or a negative error code on failure; call SDL_GetError() for more information.


This function does the actual audio data conversion, after the application has called SDL_BuildAudioCVT() to prepare the conversion information and then filled in the buffer details.

Once the application has initialized the cvt structure using SDL_BuildAudioCVT(), allocated an audio buffer and filled it with audio data in the source format, this function will convert the buffer, in-place, to the desired format.

The data conversion may go through several passes; any given pass may possibly temporarily increase the size of the data. For example, SDL might expand 16-bit data to 32 bits before resampling to a lower frequency, shrinking the data size after having grown it briefly. Since the supplied buffer will be both the source and destination, converting as necessary in-place, the application must allocate a buffer that will fully contain the data during its largest conversion pass. After SDL_BuildAudioCVT() returns, the application should set the cvt->len field to the size, in bytes, of the source data, and allocate a buffer that is cvt->len * cvt->len_mult bytes long for the buf field.

The source data should be copied into this buffer before the call to SDL_ConvertAudio(). Upon successful return, this buffer will contain the converted audio, and cvt->len_cvt will be the size of the converted data, in bytes. Any bytes in the buffer past cvt->len_cvt are undefined once this function returns.


This function is available since SDL 2.0.0.


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