Updated documentation, you don't need to initialize the audio subsystem to do in-place format conversion. (Thanks Simon Hug!)
1.1 --- a/include/SDL_audio.h Tue Aug 29 08:27:23 2017 -0700
1.2 +++ b/include/SDL_audio.h Tue Aug 29 09:02:04 2017 -0700
1.3 @@ -451,7 +451,6 @@
1.4 * and rate, and initializes the \c cvt structure with information needed
1.5 * by SDL_ConvertAudio() to convert a buffer of audio data from one format
1.6 * to the other. An unsupported format causes an error and -1 will be returned.
1.7 - * The audio subsystem must be initialized before calling this function.
1.8 *
1.9 * \return 0 if no conversion is needed, 1 if the audio filter is set up,
1.10 * or -1 on error.