Adaptive predicting circuit using a lattice filter and a corresponding differential PCM coding or decoding apparatus

An adaptive predicting circuit comprising:

• (A) a lattice filter with N identical cells (C) each having a first access port (A.sub.1), a second access port (A.sub.2), a third access port (A.sub.3) and a fourth access port (A.sub.4), the first and second access ports (A.sub.1 /m, A.sub.2 /m) of a cell (C/m) of rank m being respectively connected to the third and fourth access ports (A.sub.3 /m-1, A.sub.4 /m-1) of the preceding cell (C/m-1) of rank m-1, each cell comprising a circuit (14/m) for delaying sampling time connected to the second access port and circuits of linear combinations of signals appearing at the access ports of the cell, including first and second multipliers each having first and second inputs, one of said inputs receiving one of the signals and the other of said inputs receiving a multiplication coefficient k.sub.m (t) dependent on the sampling time t, means being provided for supplying said coefficient k.sub.m (t) to the multipliers;
• and
• (B) an adder (16) having N inputs respectively connected to the N cells and an output supplying a prediction signal;
• wherein the means for supplying the coefficient k.sub.m (t) comprise in each cell a circuit (15/m) for the sequential adaptation of the coefficient k.sub.m (t) inherent to each cell, said adaptation circuit having a first input (151/m), a second input (152/m), a third input (153/m), and a fourth input (154/m), said inputs being respectively connected to the first access port (A.sub.1 /m) of the cell, to the output of the delay circuit (14/m) and to the third and fourth access ports (A.sub.3 /m, A.sub.4 /m) of the cell, said adaptation circuit also having an output (155/m) which supplies the coefficient k.sub.m (t), the N coefficients of the lattice filter being readjusted by the N adaptation circuits for each sampling time from the signals present at this time in the filter, and the coefficients being used immediately after readjustment.