The Fraunhofer Institute, the folks behind the MP3 audio format, have unveiled MP3 surround sound technology. MP3 Surround enables high-quality surround sound at bit rates comparable to those currently used to encode stereo MP3 material. It is backwards compatible to stereo MP3; a legacy MP3 device plays back MP3 Surround as high quality stereo.
According to them, Surround MP3 files are approximately the same size as current 2-channel stereo files.
Before you worry about having to re-rip all your files, note that your audio player will need to have an MP3 Surround v2 decoder for you to enjoy multi-channel playback.
Source: TG Daily