The disclosure relates to an apparatus for encoding an input audio signal, wherein the input audio signal comprises a plurality of input audio channels. The apparatus comprises a KLT-based pre-processor configured to transform the plurality of input audio channels into a plurality of eigenchannels and to provide metadata in the form of a plurality of metadata elements, wherein the metadata allows reconstructing the plurality of input audio channels on the basis of the plurality of eigenchannels, a metadata re-arrangement unit configured to re-arrange the plurality of metadata elements on the basis of a re-arrangement scheme into one or more metadata blocks, wherein each of the one or more metadata blocks is a multi-dimensional array, and a metadata encoder configured to encode each of the one or more metadata blocks.