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 upmixer (130; 230) is configured to apply the temporarily variable upmixing parameters (150; 262) to combine one or more downmix audio signals (x(k)) with one or more de-correlated versions (q(k)) of the one or more downmix audio signals.

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 applying the temporarily variable upmixing parameters (150; 262) to combine one or more downmix audio signals (x(k)) with one or more de-correlated versions (q(k)) of the one or more downmix audio signals.

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 provide the temporarily variable upmixing parameters (150; 262) to allow for a combination of one or more downmix audio signals (x(k)) with one or more de-correlated versions (q(k)) of the one or more downmix audio signals.
, Description:Attached herewith