Time multiplexed compression - New dimensions in satellite TV

With all National Television Standard Code (NTSC) FM transmissions, a residual low frequency beat noise remains between synchronous detectors and the 3.579545 MHz chroma subcarrier used for color sync, phase and even amplitude control. Because of this, 17% of each NTSC line scan must be blank. The video compression method outlined here makes possible a reduction in the width of the horizontal sync pulse, the removal of the chroma subcarrier (also called the 'burst'), and its reinsertion in compressed form in blank space. The multiplexed component format can be derived from a standard NTSC signal using digital processing. The NTSC signal enters an eight-bit parallel A/D converter that is clocked at a multiple of the 3.58 MHz color subcarrier. Luminance and chrominance are then separated using comb filter techniques similar to those used in present-day television receivers. The comb filter employs a digital 1-h delay line and the sum and difference processing and required filtering are all done digitally.