determining, by a modulator, positions of samples to be discarded from a first memory bank that comprises modulated QMF sub-band samples by performing a first modulo operation based on sample recording positions in a previous time slot;

recording, by the modulator, at the determined positions, samples corresponding to a current time slot by replacing the samples recorded at the determined positions in the previous time slot with the samples corresponding to the current time slot;

extracting, by a synthesis filter comprising at least one processor, samples from the first memory bank, wherein positions of the samples to be extracted are determined according to whether the current time slot is an even number or an odd number;

determining, by the synthesis filter, filter coefficients corresponding to the extracted samples by performing a second modulo operation, according to the current time slot; and

obtaining, by the synthesis filter, a time domain sample by accumulating results of multiplications of the extracted samples and the determined filter coefficients.