$cvt = SDL::AudioCVT->build( $src_format, $src_channels, $src_rate
$dst_format, $dst_channels, $dst_rate );
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,
Currently (SDL-1.2.11) only rate conversions of 2x and (1/2)x with x > 0 are done, nearing the requested rate conversion.