An extended definition TV (EDTV) system which is fully compatible with the existing standards is proposed. Full compatibility implies receiver and transmission compatibility: both existing and EDTV receivers can receive existing and EDTV signals which have the same bandwidth, without adaptors. In order to insert high resolution information, vacant frequency bands are found in those areas in the first and third quadrants that conjugate with the modulated color components in the second and fourth quadrants when the signal is analyzed in the temporal-vertical frequency domain. Resolution can be improved both horizontally, by inserted high resolution information, and vertically, by progressive scanning and line interpolation. An alternate scheme is also proposed. These schemes are applicable to CATV, CCTV, video storages, broadcasting, and direct broadcasting satellites, without any modification of existing facilities.

A new run-length decoding method for facsimile signal transmission is described. In this method, if an error code is detected in a received signal, the effect is localized in the runs corresponding to the error instead of the whole line to obtain better picture quality. The error immunity in this method can be used to shorten the transmission time.