The description relates to a process for reducing data in the transmission and/or storage of digital signals from several dependent channels. The dependence of the signals in a channel, e.g. in a left and right-hand stereo channel, can be used for further data reduction. Prior art processes like central/side-band coding or the intensity stereo process result in detectable interference with an unfavourable signal composition. The process of the invention avoids such interference in that the channels are jointly coded only if the signals in both channels have similar enough spectra. In addition, it is possible with the process of the invention to attain further data reduction in that in frequency ranges in which the energy spectrum of a channel does not exceed a predeterminable fraction of the total energy spectrum, the relevant spectrum values are zeroed. As the process is independent of the specific inner structure of the coding process, it is highly versatile.