Encoding system and encoding method for encoding a digital signal having at least a first and a second digital component

An encoding system for encoding a digital signal having at least a first and a second digital signal component, the signal components having a specific sampling frequency and bandwidth, comprising

• splitter means for dividing the bandwidth of the digital signal components into M successive frequency bands, and generating in response to the digital signal components M sub signals for each digital signal component, each sub signal of a signal component being associated with one of the frequency bands,
• bit need determining means for determining bit needs for time equivalent signal blocks of the sub signals, the signal blocks each containing q samples of a sub signal, a bit need b.sub.mi for a signal block of a sub signal SB.sub.mi of a signal component i in frequency band m corresponding to the number of bits by which the q samples in that signal block should be represented, where b.sub.mi may vary for different signal blocks and different sub signals,
• signal combination means for combining, in a number of at least one frequency bands, time equivalent signal blocks of corresponding sub signals of the at least first and second signal component so as to obtain a time equivalent signal block of a composite sub signal in each said at least one frequency bands,
• quantizing means for quantizing time equivalent signal blocks of the sub signals in those frequency bands in which no composite sub signal is available and for quantizing the corresponding time equivalent signal blocks of the composite sub signal in said at least one frequency band in which a composite sub signal is available, each sample of the signal block of a sub signal SB.sub.mi being quantized by n.sub.mi bits, where m denotes a frequency band in which no composite sub signal is available, and each sample of the composite sub signal SB.sub.mc being quantized by n.sub.mc bits, where m denotes a frequency band in which a composite sub signal is available,
• bit allocation means for deriving the variables n.sub.mi and n.sub.mc from bit needs obtained in the bit need determining means and from a value B, where B corresponds to a number of bits in an available bitpool, and wherein q is an integer larger than zero, n.sub.mi, n.sub.mc, b.sub.mi, b.sub.mc are variables where n.sub.mi and n.sub.mc are greater than or equal to zero, M is a constant greater than zero, B is an integer, and m is an integer such that 1.ltoreq.m.ltoreq.M, characterized in that the bit need determining means is adapted to determine a common bit need b.sub.mc for a time equivalent signal block of a composite sub signal SB.sub.mc in a frequency band m from the bit needs b.sub.mi of the time equivalent signal blocks of the corresponding sub signals of the at least two signal components in that frequency band from which the time equivalent signal block of the composite sub signal has been derived, such that common bit need b.sub.mc is equal to the sum of the bit needs b.sub.mi, multiplied by a corresponding weighting factor, the bit allocation means being adapted to derive the variables n.sub.mi for the time equivalent signal blocks of the sub signals in those frequency bands in which no composite sub signal is available and the at least one variable n.sub.mc for the time equivalent signal block of the sub signal in those at least one frequency band for which a composite sub signal is available, from the bit needs b.sub.mi available for those frequency bands for which no composite sub signal is available and the at least one common bit need b.sub.mc.