A method for parametric encoding of a multi-channel digital audio signal. The method includes encoding a mono signal from channel-reduction processing applied to the multi-channel signal and encoding spatialisation information of the multi-channel signal. The channel-reduction processing includes the following steps, implemented for each spectral unit of the multi-channel signal: extracting at least one indicator characterizing the channels of the multi-channel digital audio signal; selecting, from a set of channel-reduction processing modes, a channel-reduction processing mode in accordance with the value of the at least one indicator characterizing the channels of the multi-channel audio signal. Also provides are a corresponding encoding device and a processing method which includes the channel-reduction processing.