This paper describes a time-domain algorithm to upmix stereo recordings for an enhanced playback on a surround sound loudspeaker setup. It is mainly the simplified version of a previously published frequency-domain algorithm where the standard shorttime Fourier transform is now replaced by an IIR filter bank. The design of complementary filter blocks and their arrangement in a tree structure to form a filter bank are derived. The arithmetic complexity of the filter bank itself and of the complete upmix algorithm is analysed and compared to the frequency-domain approach. The time-domain upmix is less flexible in its configuration but achieves an audio quality comparable to the frequency-domain implementation at a fraction of its computational cost.

Download