Digital transmission system using subband coding of a digital signal

Abstract

A digital transmission system is disclosed having a transmitter (3,6,9) and a receiver (13,16,19) for transmitting a digital signal, such as a digital audio signal, having a given sampling rate F.sub.S. The digital signal is subband coded into M subbands with sampling rate reduction. To that purpose the transmitter includes a first unit (3) for splitting up the digital signal into M signals having a sampling rate F.sub.S /M. These signals are available at the outputs (4.1 to 4.M) of the first unit (3), and are applied to M analysis filters (6.1 to 6.M), each filter (6.m) having one input (5.m) and two outputs (7.ma and 7.mb). The 2M filter outputs are coupled to 2M inputs (8.1 to 8.2M) of a signal processing unit 9 which has M outputs (10.1 to 10M) for supplying the M subband signals (S.sub.1 to S.sub.M). Each filter (6.m) is adapted to apply two different filterings on the signal applied to its input and to supply the two different filtered versions of the input signal to its two outputs. The signal processing unit 9 is adapted to supply output signals on each of the M outputs, an output signal being a combination of at least a number of input signals applied to its 2M inputs. On the receiver side a signal processing is carried out which is largely inverse to the signal processing on the transmitter side, in order to realize a signal at the output (21) that is a nearly perfect reconstruction of the input signal.