Encoding system comprising a subband coder for subband coding of a wideband digital signal constituted by first and second signal components

An encoding system comprising a subband coder for subband digital coding of an information signal constituted by at least first and second signal components, said subband coder including:

• signal splitting means, responsive to said information signal, for splitting said information signal into M successive subbands and generating digital subband signals comprising a succession of signal blocks, in a subband SB.sub.m a succession of first and second corresponding time-equivalent signal blocks respectively containing samples of first and second subband signal components related to said first and second signal components, and
• quantizing means for quantizing block-by-block said samples of first and second subband signal components in the subband SB.sub.m to form quantized signal blocks, said samples in one pair of corresponding quantized signal blocks in said subband SB.sub.m being represented by n.sub.m1 and n.sub.m2 bits respectively,
• said quantizing means comprising:
• bit need means for determining a respective bit need b for respective signal blocks in the M subbands, said respective bit need being related to the number of bits by which said samples in said signal blocks in respective ones of the M subbands should be represented,
• bit allocation means, responsive to the bit needs determined in the bit need means, for allocating an available quantity of bits to respective samples in the different signal blocks in the M subbands,
• determining means for determining, for one signal block of said pair, whether an initial allocation of bits to the samples in said one signal block is to be performed in the bit allocation means irrespective of the bit need of said one signal block determined by said bit need means;
• and
• means for producing a first SB.sub.m control signal responsive to the determination by said determining means,
• said bit allocation means being responsive to said first SB.sub.m control signal, for initially allocating a first number of bits to the samples of said one signal block, and for initially allocating a second number of bits to the samples of the other block of said pair irrespective of the bit need of said other block determined by said bit need means.

An encoding system comprising a subband coder for subband digital coding, including coding in an intensity mode, of an information signal constituted by at least first and second signal components, including:

• signal splitting means, responsive to said information signal, for splitting said information signal into M successive subbands and generating digital subband signals comprising a succession of signal blocks, in a subband SB.sub.m a succession of first and second corresponding time-equivalent signal blocks respectively containing samples of first and second subband signal components related to said first and second signal components,
• means for combining corresponding samples of the first and second subband signal components of a subband SB.sub.p, where p.noteq.m, to obtain a combined subband signal, and quantizing the combined subband signal to provide a quantized combined subband signal constituted by combined signal blocks each containing q samples, the q samples in a combined signal block of the quantized combined subband signal each being represented by n.sub.pc bits, and
• quantizing means for quantizing block-by-block the samples of first and second subband signal components in the subband SB.sub.m to form component signal blocks, the samples in a pair of corresponding component signal blocks of the first and second quantized subband signal components in said subband SB.sub.m being represented by n.sub.m1 and n.sub.m2 bits respectively,
• wherein said quantizing means comprises:
• bit need means for determining a respective bit need b for respective signal blocks in the subbands, said bit need being related to the number of bits by which the samples in a signal block in a respective subband should be represented,
• bit allocation means, responsive to the bit needs determined in the bit need determining means, for allocating an available quantity of bits to respective samples in the different signal blocks in the M subbands, and
• determining means for determining, for a particular signal block of the first subband signal component in the subband SB.sub.m, whether an initial allocation of a number of bits to the samples in said particular signal block is to be performed in the bit allocation means irrespective of the bit need b of particular signal block determined by said bit need means,
• and wherein:
• for the subband SB.sub.p, said determining means evaluates each signal block of an SB.sub.p pair of corresponding time-equivalent signal blocks prior to combining of the corresponding samples, and said means for producing produces a first SB.sub.p control signal if said initial allocation is to be performed for one signal block of said SB.sub.p pair,
• said means for combining and quantizing then combines corresponding samples of the first and second subband signal components in the subband SB.sub.p to obtain said combined subband signal which is then quantized, and
• said bit allocation means, responsive to said first SB.sub.p control signal, initially allocates a third number of bits to the samples of said combined subband signal.