A STUDY ON 3-DIMENSIONAL (SPATIOTEMPORAL) NOISE CHARACTERISTICS OF LETTERBOX EDTV

TheF difference between the three-dimensional noise characteristics of the current NTSC and that of the letterbox EDTV has been studied. Her eafter, we use ''three-dimensional'' for spatio-temporal. We have show n that when the letterbox EDTV pictures (main panel) are displayed in the 16:9 aspect area with the same picture height as that of NTSC pict ures (4:3), and when the signal levels are the same, the three-dimensi onal noise power spectrum of the main panel of letterbox EDTV is trans formed into a low spatial frequency region with high density, and the total noise power remains unchanged both in NTSC and EDTV. The helper signals which are multiplexed onto the black bands in the top and bott om portions of the screen, generally, increase the total noise power o f decoded EDTV signals even if the amplitude of the helper signals is large enough. By applying a three-dimensional weighting function, it i s shown that; the weighted noise power of the letterbox EDTV becomes l arger than that of NTSC. Hence, in order to retain the existing servic e area after introducing the EDTV broadcasting service, it will be nec essary to install noise suppressing measures in the EDTV system.