Apparatus and Method for Stereo Filling in Multichannel Coding

Apparatus for decoding a previous encoded multichannel signal of a previous frame to obtain three or more previous audio output channels, and for decoding a current encoded multichannel signal of a current frame to obtain three or more current audio output channels,

• wherein the apparatus comprises a channel decoder, a multichannel processor for generating the three or more current audio output channels, and a noise filling module,
• wherein the channel decoder is adapted to decode the current encoded multichannel signal of the current frame to obtain a set of three or more decoded channels of the current frame,
• wherein the multichannel processor is adapted to select a first selected pair of two decoded channels from the set of three or more decoded channels identified by first multichannel parameters,
• wherein the multichannel processor is adapted to generate a first group of two or more processed channels based on said first selected pair of two decoded channels to obtain an updated set of three or more decoded channels,
• wherein, before the multichannel processor generates the first group of two or more processed channels based on said first selected pair of two decoded channels, the noise filling module is adapted to identify for at least one of the two channels of said first selected pair of two decoded channels, one or more frequency bands, within which all spectral lines are quantized to zero, and to generate a mixing channel using two or more, but not all of the three or more previous audio output channels, and to fill the spectral lines of the one or more frequency bands, within which all spectral lines are quantized to zero, with noise generated using spectral lines of the mixing channel, wherein the noise filling module is adapted to select the two or more previous audio output channels that are used for generating the mixing channel from the three or more previous audio output channels depending on the first multichannel parameters,
• characterized in that,
• the noise filling module is configured to determine if stereo filling is not used depending on an indicator, and, if stereo filling is used, the noise filling module is configured to undo scale factor application, if it was previously applied to a channel spectrum of said at least one of the two channels of said first pair.