RIFF-WAV means a MP3 or MP2 file with the RIFF-WAV header which makes MP3 or MP2 looks like a WAV file and the extension is .wav. If you have installed a Windows Codec to decompress MP3 Files, this function might be useful. Since Windows takes care of the decompression, even applications that are not aware of the MP3 format can handle this file format via the Windows Codec.