A double-rate signal achieved by subjecting a video signal to double-rate conversion
is supplied to a scan line number converter, wherein the portion of the effective
scan lines of the double-rate signal is written into a frame memory based on a
signal achieved by multiplying horizontal and vertical synchronous signals of the
double-rate signal. In the effective scan line section of an HDTV signal, the video
signal written in the frame memory is read out based on horizontal and vertical
reference signals of the HDTV signal. Out of the effective scan line section of
the HDTV signal, a pedestal level signal written in a memory is read out based
on the horizontal and vertical reference signals of the HDTV signal, thereby achieving
an HDTV signal whose vertical scan line number is equal to 1125 lines. Accordingly,
the HDTV signal suffers no degradation because the video signal in the section
of 960 effective scan lines of the double-rate signal is not interpolated
