Abstract: In the process of generating a compatible 4:3 letterbox format television signal, a wide aspect ration 16:9 progressive scan television signal is vertically transcoded from 575 to 431 image lines, converted to line interlaced form and horizontally compressed. A vertically transcoded interlaced luminance component is converted back to progressive scan form via interpolation, and subtracted from a vertically transcoded original progressive scan luminance component to produce a difference (helper) signal. The difference signal is time compressed and multiplexed into upper and lower edge bar regions of the letterbox format. The compatible letterbox signal also is encoded with additional information including vertical high frequency information and horizontal high frequency information separated during the transcoding and compression processes, respectively. The encoding includes modulating the color subcarrier frequency with luminance information, and intraframe averaging.

Abstract: Video signal information derived from a high definition source is conveyed via two channels. A first channel conveys relatively low spatial resolution, high temporal resolution video information compatible with a standard television receiver. An auxiliary second channel conveys relatively high spatial resolution, low temporal resolution video information. A high definition television receiver reconstructs original high definition information from the first and second channel information.