| 摘要 |
Subcarrier is regenerated digitally from a video signal which has a line frequency that cannot be assumed to be constant. Subcarrier samples at the line-locked frequency are compared, using digital or analogue means, with a reference subcarrier derived from a crystal locked oscillator. The frequency of the subcarrier samples is controlled in feedback to produce subcarrier of accurate frequency in the line-locked digital environment. |
