NORMAL SYSTEM CONVERTING DEVICE

PURPOSE:To prevent the turbulence of a screen image accompanying the up-and- down inversion of a scanning line by deciding the point of time when the odd and the even fields of a video signal read out from a memory change places with each other, and shifting the phase of a vertical synchronizing signal by one horizontal scanning period. CONSTITUTION:Means 21, 22 to decide the point of time when the odd end the even fields of the video signal read out from the memory 9 change places with each other, and the means 23 to shift the vertical synchronizing signal to be added to the video signal read out from the memory 9 or the read-out timing of the memory 9 by one horizontal scanning period on the basis of this decision are provided. Then, the point of time when the odd and the even fields of the video signal read out from the memory 9 change places with each other is decided, and the field in which the scanning lines of the odd and the even fields are inverted up and down by the video signal is detected, and the scanning line of the even field is shifted by a one horizontal scanning period portion on the basis of this detected result. Thus, the up-and-down inversion of the scanning line can be canceled.