i'd like to build a "digital audio player", because i have an external disk with thousands of music materials, APE, FLAC, WAV, ... i don't want to take to trouble to open the computer everytime i want to listen to my music.

so my player is gonna be like, everything i do is to plug in my disk (via a usb cable or something), then i can choose to play any one of the musics i'd like to hear.

but i've got no idea of how to make such thing. surely there must a decoder, but how should i deal with the input and the output part?

hope someone experienced could help me :-)

I think you're going to be hard pressed to find a readily available DIY chip that decodes APE and FLAC.

There are, however, MP3 decoders available. DIY MP3 Player

One possible alternative would be to find a commercial player that supports flac and ape, find a broken one on ebay or somewhere, and then fix it and hack in your larger hard drive. No easy task...

Maybe this might be the ticket?