A study on three-dimensional (spatio-temporal) noise characteristics of letterbox EDTV

The difference between the three-dimensional noise characteristics of the current NTSC and that of the letterbox EDTV has been studied. We have shown 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 pictures (4:3), and when the signal levels are the same, the three-dimensional noise power spectrum of the main panel of letterbox EDTV is transformed 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 bottom portions of the screen, generally, increase the total noise power of decoded EDTV signals even if the amplitude of the helper signals is large enough. By applying a three-dimensional weighting function, it is shown that the weighted noise power of the letterbox EDTV becomes larger than that of NTSC. Hence, in order to retain the existing service area after introducing the EDTV broadcasting service, it will be necessary to install noise suppressing measures in the EDTV system