Band compressing/restoring apparatus

摘要

In a band compression apparatus, an input signal is separated into high- and low-frequency components H and L by an LPF and an adder. The component H is in-frame-averaged by an in-frame average circuit. The component L is output as a signal S3 having a large energy via a field delay circuit and a switch circuit. An in-frame difference of the low-frequency component L is obtained by a field delay circuit and an adder. This in-frame differential signal S2 is added to an in-frame average signal S1 by an adder. A signal S4 having a small energy is obtained by this addition. In a band restoration apparatus the signals S3 and S4 are separated into signals of two fields by an adder and a switch circuit. A signal S5 consisting of the components L and H is obtained in one field. A signal S2 consisting of only the component L is obtained in the other field. The signal S5 is output via a switch circuit. The signal S2 is added to the signal S5 in an immediately preceding field by an adder. A signal S6 consisting of the components L and H is obtained by this addition. The signal S6 is output via the switch circuit at a timing delayed by one field with respect to the signal S5.