Abstract

The decoder of this invention decodes at least two channel signals in a directional information system where at least four input signals containing directional information have been encoded into the two or more channel signals. The decoder generates a first control signal substantially proportional to the logarithm of the ratio of the amplitudes of two of the channel signals to detect, as between two of the channel signals, whether the amplitude of one signal dominates that of the other. The decoder also generates a second control signal substantially proportional to the logarithm of the ratio of the amplitudes of the sum and the difference between two of the channel signals to detect the dominant signal in terms of amplitude. The decoder includes a matrix means responsive to the two or more channel signals and the two control signals for generating a number of output signals according to an algorithm. The control signals generated are used to steer the directional information systems in such manner through the matrix means that the directional effects of the output signals are enhanced. Two decoders of the type described above may be used to decode the high frequency and low frequency portions of the channel signals where the high and low frequency portions are separated by means of two crossover filters. The crossover frequency of the two crossover filters is controlled so that it is approximately at the top end of the signal frequencies intended for the center loudspeaker. Very low frequency signal components are separately processed and evenly distributed among the left, center and right channels.

Other References

• "Four Channels and Compatibility" by Peter Scheiber, Journal of the Audio Engineering Society, Apr. 1971, vol. 19, No. 4, pp. 267-279
• "Surround Sound in the Eighties--Advances in Decoder Technology" by Martin E. G. Willcocks presented at the 74th Convention of the Audio Engineering Society, Oct. 1983, N.Y