The paper presents a very simple enhancement of joint coding
of stereo and surround channels within a perceptual
audio codec. Moreover, the paper proposes two improvements
to standard parametric stereo and spatial audio compression
in order to avoid the smearing of transients in the
process of channel downmixing. The improvements consist
in compensating of inter-channel delays prior to mixdown,
as well as additional encoding of the room response for realistic
reconstruction of the stereo ambience.