Before an SDL_AudioCVT structure can be used to convert audio data it must be initialized with source and destination information.
src_format and dst_format are the source and destination format of the conversion. (For information on audio formats see SDL_AudioSpec). src_channels and dst_channels are the number of channels in the source and destination formats. Finally, src_rate and dst_rate are the frequency or samples-per-second of the source and destination formats. Once again, see SDL_AudioSpec.