| 摘要 |
A clock range setting device including a horizontal counter, a filter unit, a clock detecting unit, a first infinite impulse filter (IIR filter), and a clock range modulator is provided. The horizontal counter counts a horizontal counter value. The filter unit obtains a lead clock of each teletext video signal according to a lead clock range, and generates a corresponding clock intermediate value. The clock detecting unit detects level changes of the lead clock of each teletext video signal according to the clock intermediate value, so as to generate a corresponding current clock cycle number. The first IIR filter generates corresponding number mean value according to the current clock cycle numbers sequentially received by the first IIR filter. The clock range modulator sets the lead clock range corresponding to each teletext video signal according to the current clock cycle number, the number mean value, and the horizontal counter value.
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