Claims:We Claim

1. An apparatus (100; 200) for upmixing a downmix audio signal (110; 210) describing one or more downmix audio channels into an upmixed audio signal (120; 214) describing a plurality of upmixed audio channels, the apparatus comprising:

an upmixer (130; 230) configured to apply temporally variable upmix parameters (150; 262; Hij) to upmix the downmix audio signal (110; 210) in order to obtain the upmixed audio signal (120; 214); and

a parameter interpolator (140; 260), wherein the parameter interpolator is configured to obtain one or more temporally interpolated upmix parameters (150; 262) to be used by the upmixer (130; 230) on the basis of an information describing a first complex-valued upmix parameter (142) and a subsequent second complex-valued upmix parameter (144),

wherein the parameter interpolator (140; 260) is configured to separately interpolate

(a) between a magnitude value (254) of the first complex- valued upmix parameter (142) and a magnitude value (254) of the second complex-valued upmix parameter (144), and

(b) between a phase value (256) of the first complex- valued upmix parameter (142) and a phase value (256) of the second complex-valued upmix parameter (144),

to obtain the one or more temporally interpolated complex-valued upmix parameters (150; 262);

wherein the apparatus is configured to receive spatial cues (ILD, ICC, ITD, IPD) describing the upmix parameters.

2. A method for upmixing a downmix audio signal (110; 210) describing one or more downmix audio channels into an upmixed audio signal (120; 214) describing a plurality of upmixed audio channels, the method comprising:

applying temporally variable upmix parameters (150; 262; Hij) to upmix the downmix audio signal (110; 210) in order to obtain the upmixed audio signal (120; 214); and

obtaining one or more temporally interpolated upmix parameters (150; 262) to be used by the upmixer (130; 230) on the basis of an information describing a first complex-valued upmix parameter (142) and a subsequent second complex-valued upmix parameter (144),

wherein the method comprises separately interpolating

(a) between a magnitude value (254) of the first complex- valued upmix parameter (142) and a magnitude value (254) of the second complex-valued upmix parameter (144), and

(b) between a phase value (256) of the first complex- valued upmix parameter (142) and a phase value (256) of the second complex-valued upmix parameter (144),

to obtain the one or more temporally interpolated complex-valued upmix parameters (150; 262);

wherein the method comprises receiving spatial cues (ILD, ICC, ITD, IPD) describing the upmix parameters.

3. A parameter determinator (140; 260) for determining temporally variable upmix parameters for upmixing a downmix audio signal (110; 210) describing one or more downmix audio channels into an upmixed audio signal (120; 214) describing a plurality of upmixed audio channels,

wherein the parameter determinator comprises a parameter interpolator,

wherein the parameter interpolator is configured to obtain one or more temporally interpolated upmix parameters (150; 262) to be used by an upmixer (130; 230) on the basis of an information describing a first complex-valued upmix parameter (142) and a subsequent second complex-valued upmix parameter (144),

wherein the parameter interpolator (140; 260) is configured to separately interpolate

(a) between a magnitude value (254) of the first complex- valued upmix parameter (142) and a magnitude value (254) of the second complex-valued upmix parameter (144), and

(b) between a phase value (256) of the first complex- valued upmix parameter (142) and a phase value (256) of the second complex-valued upmix parameter (144),

to obtain the one or more temporally interpolated complex-valued upmix parameters (150; 262);

wherein the parameter determinator is configured to receive spatial cues (ILD, ICC, ITD, IPD) describing the upmix parameters.

, Description:As Attached