The Decoder~ Module

This module can be used to apply spectral and temporal corrections to the output signals of the Pan~ module, before sending these signals to the loudspeakers. Each channel undergoes an adjustable time delay and a double shelving filter of the type described in section.

The filters can be used to equalize the frequency response of each loudspeaker separately (note that more elaborate equalizers could be used, as mentionned in section). The delays can be used to make the signal propagation delays of all channels identical. Differences between these propagation delays can be introduced both by the geometry of the loudspeaker setup and the hardware configuration of the host computer.

Nota Bene: These corrections should be made so that all loudspeakers should be perceived, from the reference listening position, as being situated at the same distance and having approximately the same frequency response. The necessary delay and filter adjustments can be automatically derived from impulse response measurements made at the reference position for each loudspeaker (a software allowing to do this exists at Ircam but has not yet been implemented in the Spat~ library).