| 摘要 |
In a known copy protection process for preventing recording of video signals, pseudo sync and AGC pulses (Fig. 2) are present on predetermined lines within the blanking intervals of the video signal so that any subsequent video signal shows a picture of very low entertainment quality. The location of the video lines containing the copy protection is determined by using the color burst signal or chroma in the horizontal blanking interval. Then some or all of the lines including copy protection signals may be modified so as to render the overall video signal recordable. The modification is accomplished in a number of ways, including gain shifting portions of the video signal, level shifting portions of the video signal, bandwidth limiting certain portions of the video signal or replacing certain portions of the video signal with other video elements.
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