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Exploring and Exploiting Subchannels in the NTSC Spectrum

1988; Society of Motion Picture and Television Engineers; Volume: 97; Issue: 7 Linguagem: Inglês

10.5594/j02918

0036-1682

Michael Isnardi,

Color Science and Applications

When the NTSC spectrum is analyzed in three dimensions, regions of high spatiotemporal frequencies that have several important properties can be identified. First, these regions contain little energy for scenes of normal picture content. Second, they contain frequencies, such as those corresponding to moving diagonals, that are largely ignored by the human visual system. Third, they are not interpreted as normal color by most NTSC receivers. These properties allow the insertion of additional, possibly uncorrelated, video information into prefiltered "holes" or "subchannels" in the multidimensional spectrum. Ignored by the circuits of standard NTSC receivers and the eyes of their viewers, this extra information can be detected, removed, and displayed by special receivers. Exploiting subchannels in the NTSC spectrum can increase the amount of transmitted video information in a fully compatible manner. This article describes the location of the NTSC subchannels, and illustrates how they can be used in a typical application.