A multichannel audio format provides a truly discrete as well as a backward compatible mix for surround-sound, front or other discrete audio channels in cinema, home theater, or music environments. The additional discrete audio signals are mixed with the existing discrete audio channels into a predetermined...http://www.google.co.uk/patents/US7212872?utm_source=gb-gplus-sharePatent US7212872 - Discrete multichannel audio with a backward compatible mix
