| 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 tape recording of the video signal shows a picture of very low entertainment quality. This copy protection process is defeated first by determining the location of the video lines containing the copy protection using the color burst signal or chroma in the horizontal blanking interval to determine online detection (Fig. 4). Then some or all of the lines including copy protection signals are 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 (Fig. 5).
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