Nero just released a free MPEG-4/3GPP encoder/decoder software package for Windows.

• Compression Ratios ranging from ultra high (58 CDs fit on one!) to High-End Audio (2.5:1), for absolutely perfect audiophile encodings
• Crystal Clear, Award Winning Sound Quality at every compression ratio and bit rate!
• Support for Embedded Album Art (Covers, Booklets, Lyrics!)
• Store Entire Audio Album in a Single .mp4 File with all the Features of an Audio CD embedded inside, but at a fraction of the space!
• Reference Quality MPEG-4 Audio Codec
• Fully Compatible with the Latest Version of the State-of-the-art MPEG-4 Audio Standard (LC-AAC, HE-AAC and HE-AAC v2)

Source: Nero Digital Audio