Patent ID: 7564978

Claim:
An apparatus for encoding a stereo signal to obtain a mono output signal and a stereo parameter set, comprising: a means for calculating the mono signal by combining a left and a right channel of the stereo signals; a means for generating a first stereo parameter set using a portion of the left channel and a portion of the right channel, the portion starting at a first time border; a means for determining a validity of the first stereo parameter set for subsequent portions of the left channel and the right channel, wherein the determiner for determining is operative to: generate second time border, and activate the generator for generating, when it is determined that the stereo parameter set is not valid anymore so that a second stereo parameter set for portions of the left and right signals starting at the second time border is generated; and a means for outputting the mono signal and the first stereo parameter set and the first time border associated with the first parameter set, and the second stereo parameter set and the second time border associated with the second stereo parameter set.