PURPOSE: To realize a small sized and inexpensive picture processing unit by implementing expansion and time base error correction to a picture signal with a different aspect ratio.

CONSTITUTION: This processing unit uses an A/D converter 32, a buffer memory 33, a D/A converter 34, a synchronizing separator circuit 36, a PLL circuit 37, a write address generator 38 and a read address generator 39 in common and a clock from a clock generating circuit 41 is inputted to a frequency divider 40. A frequency division ratio (1/N) of the frequency divider 40 is set by a command discrimination circuit 42 based on an input command so as to be equivalent that an output signal from the buffer memory 33 is subject to horizontal time direction expansion processing and segmentation processing for a horizontal valid period simultaneously. Since the clock generating circuit 41 does not include any time base error, an output picture signal from the buffer memory 33 includes no time base error.