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 parameter interpolator (140; 260) is configured to monotonically time-interpolate between the magnitude value (254) of the first complex-valued upmix parameter (142) and the magnitude value (254) of the second complex-valued upmix parameter (144), to obtain magnitude values (274) of the one or more temporally interpolated upmix parameters (150; 262),

to linearly time-interpolate between the phase value (256) of the first complex-valued upmix parameter (142) and the phase value (256) of the second complex-valued upmix parameter (144), to obtain phase values (276) of the one or more temporally interpolated upmix parameters, and

to combine the one or more interpolated magnitude values (274) with one or more corresponding interpolated phase values (276), to obtain the one or more complex-valued temporally interpolated upmix parameters (150; 262).

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 monotonically time-interpolating between the magnitude value (254) of the first complex-valued upmix parameter (142) and the magnitude value (254) of the second complex-valued upmix parameter (144), to obtain magnitude values (274) of the one or more temporally interpolated upmix parameters (150; 262),

linearly time-interpolating between the phase value (256) of the first complex-valued upmix parameter (142) and the phase value (256) of the second complex-valued upmix parameter (144), to obtain phase values (276) of the one or more temporally interpolated upmix parameters, and

combining the one or more interpolated magnitude values (274) with one or more corresponding interpolated phase values (276), to obtain the one or more complex-valued temporally interpolated upmix parameters (150; 262).

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 interpolator (140; 260) is configured to monotonically time-interpolate between the magnitude value (254) of the first complex-valued upmix parameter (142) and the magnitude value (254) of the second complex-valued upmix parameter (144), to obtain magnitude values (274) of the one or more temporally interpolated upmix parameters (150; 262),

to linearly time-interpolate between the phase value (256) of the first complex-valued upmix parameter (142) and the phase value (256) of the second complex-valued upmix parameter (144), to obtain phase values (276) of the one or more temporally interpolated upmix parameters, and

to combine the one or more interpolated magnitude values (274) with one or more corresponding interpolated phase values (276), to obtain the one or more complex-valued temporally interpolated upmix parameters (150; 262).
, Description:Attached herewith