Patent ID: 8179443

Claim:
A waveform display apparatus for receiving an external reference video signal and a video signal under test and displaying the video signal under test as a waveform on a display in both an internal reference mode and an external reference mode comprising: means for selecting between the internal reference mode and the external reference mode; means for adjusting a phase relationship by adding a phase offset to one of the external reference video signal and the video signal under test; a memory for storing the phase offset; a controller reading the phase offset for controlling the adjusting means to adjust the phase relationship between the external reference video signal and the video signal under test; and means for detecting the format of the video signal under test, wherein the memory stores the phase offset based upon the format of the video signal under test and the controller reads out the phase offset according to the detected format of the video signal under test and controls the means for adjusting the phase relationship to adjust the phase relationship between the external reference video signal and the video signal under test.