WAV is uncompressed. MP3 is highly compressed, but lossy. FLAC is compressed and lossless. If you wanted to store lots of master copies of audio, you could use WAV or you could reduce storage space by using FLAC instead.
MP3 is more like an edited version of the original where "extra fluff" is removed from the audio in a way that you can still hear the important bits. And then compressed for further space savings.
Obviously, there is no point in converting MP3 to FLAC since when the original lossless audio track was MP3'd , it lost some of the audio information, so you'd only be changing the compression algorithm, I imagine.
I'm really confused by what you're talking about lol... especially "up"convert...??? WAV is the ultimate lossless audio on PC. It really doesn't get any better than WAV. There is no "up" from WAV. FLAC is a compression format for WAV, that does not lose any data. The output of FLAC will be identical to the WAV file, even though its compressed. MP3 is a compression format for WAV that loses data, and will not be identical to the original WAV file.
In 1988, Apple developed the Audio Interchange File Format (AIFF), which is uncompressed pulse code modulation (PCM). PCM is what is stored on CDs, so any Mac with a CD-ROM drive attached will recognize the PCM information on Red Book audio CD's as AIFF files.
Inexplicably, 3 years later, Microsoft and IBM developed the Resource Interchange File Format (RIFF) in 1991, of which the WAV format is one implementation. RIFF doesn't store PCM. Instead it stores various formats of data in 4 byte "chunks."
Depending on the audio file format specified, one can always distinguish a Windows user from an audio professional (or a Mac user), because since about 1990, the vast majority of professional audio recording (tracking, mixing and mastering) studios have been exclusively Mac shops, including such greats as Skywalker Sound and Abbey Road Studios.
All these formats, IFF, AIFF, and RIFF, use named chunks for organization, and store PCM basically the same way, though there are other payloads possible.
https://xiph.org/flac/documentation_tools_flac.html#flac_opt...