Compatible matrix-encoded surround-sound channels in a discrete digital sound format

This invention relates to the field of multichannel audio. More particularly the invention relates to matrix-encoded surround-sound channels in a discrete typically digital sound format for motion picture soundtracks. Three surround sound channels are provided within the current formats of the Dolby Digital, Sony SDDS and DTS digital soundtrack systems in a manner that provides compatibility with conventional two surround channel playback in standard 5.1 channel and 7.1 channel systems while allowing the soundtrack preparer to send the same signal to all surround sound channels and preserving the ability to pan among the three matrix decoded surround sound channels in an arrangement that employs an active matrix decoder to provide the three surround sound channels.