| 摘要 |
Novel means are disclosed for conditioning a standard color-television composite signal, such as the NTSC composite, so that pictorial information is represented according to Nyquist samples which are very coarsely quantized and therefore regenerable. This conditioning does not affect compatibility with a standard receiver or perceptibly reduce the quality of a picture displayed thereon. Carefully designed dither, such as 3-dimensional nasik dither, is employed to preserve picture information and quality despite coarse quantization. An improved receiver also regenerates the received signal so that unwanted noise, distortion and interference are removed. The disclosure exemplifies the teachings of the invention in terms of broadcast and cable television systems and video recording systems. An improved videodisk record is disclosed and means whereby, in a pay-television system, the picture incorporated into a standard composite signal may be key-encrypted according to a private cryptographic key.
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