Abstract: Method of adaptive differential pulse code modulation, ADPCM, which fundamentally satisfies the recommendations G.726 or G.727 of the CCITT, being implemented in an ADPCM encoder whereby, given an input sample, a quantified difference signal (DQ) is obtained by subtracting from the input sample an estimated value of this sample, the estimated signal (SE), whereby a feedback loop is formed which includes a prediction module (27). The prediction module (27) calculates, in the preceding frame, the estimated signal (SE) and a partial estimated signal of the sixth order prediction for the current frame sample. Consequently these operations are carried out in parallel with other of the algorithm, resulting in an overall speeding up of the encoding process.

Abstract: The present invention relates to a frequency synthesizer for generating an output signal (So) the frequency of which has a non-integer, fractional relationship of value Nn/Nd, where Nn and Nd are integer numbers, with respect to a frequency (fr) of an input signal (Sr). The synthesizer is characterized in that it comprises a device for multiplying by M, where M is an integer number, the frequency of the input signal in order to produce a high frequency intermediate signal (Si), and a device for dividing the frequency of this intermediate signal by (M×Nd)/Nn in order to generate the output signal (So).