Apparatus and method for detecting vertical blanking interval signals
View Patent ↗An apparatus for detecting vertical blanking interval (VBI) signals and an associated detecting method are disclosed. The apparatus can reduce the probability of false alarm by dynamically adjusting the range of a detection window within the VBI interval, thereby enhancing the detection accuracy. The apparatus includes a detection unit and a window-adjusting unit. The detection unit detects whether a television signal contains a clock run-in signal within the detection window to generate a detection signal. The window-adjusting unit dynamically adjusts the range of the detection window according to the detection signal.
1. An apparatus for detecting a vertical blanking interval (VBI) signal comprising:
a detection unit for detecting whether a TV signal contains a clock run-in signal within a detection window and generating a detection signal; and
a window-adjusting unit, coupled to the detection unit, for dynamically adjusting a range of the detection window according to the detection signal; wherein the window-adjusting unit comprises:
an acquisition window for indicating a first range of the detection window;
a tracking window for indicating a second range of the detection window; and
a multiplexer for selecting one of the first range and the second range and outputting the selected range to the detection unit; wherein the second range is substantially smaller than the first range.
2. The apparatus of claim 1 , wherein the detection unit determines whether the clock run-in signal is detected according to a level value of the TV signal within the detection window.
3. The apparatus of claim 2 , further comprising:
a signal conversion unit for sampling the TV signal to generate a plurality of sampled values to the detection unit;
wherein the detection unit compares the sampled values in the detection window with a threshold to determine whether the clock run-in signal is detected.
4. The apparatus of claim 3 , wherein the threshold is determined according to a reference level and the reference level is determined according to a plurality of level values of the TV signal in a reference window.
5. The apparatus of claim 3 , wherein the detection signal indicates a current position information of the clock run-in signal, and the window-adjusting unit dynamically determines a positioning point of the detection window according to the current position information.
6. The apparatus of claim 5 , wherein the positioning point represents a center point of the detection window.
7. The apparatus of claim 5 , wherein the window-adjusting unit performs an alpha blending operation on the current position information to determine the positioning point.
8. The apparatus of claim 1 , wherein the window-adjusting unit dynamically adjusts the range of the detection window according to a detection rate of the clock run-in signal.
9. The apparatus of claim 1 , wherein the tracking window dynamically adjusts the second range according to the detection signal.
10. The apparatus of claim 1 , wherein the multiplexer selects one of the first range and the second range according to a detection rate of the clock run-in signal, and outputs the selected range to the detection unit.
11. The apparatus of claim 10 , wherein the multiplexer selects the second range when the detection rate of the clock run-in signal is higher than a first predetermined value.
12. The apparatus of claim 10 , wherein the multiplexer selects the first range when the detection rate of the clock run-in signal is lower than a second predetermined value.
13. The apparatus of claim 1 , wherein the VBI signal conforms to one of the following specifications: Closed Caption (CC), Copy Generation Management System (CGMS), Wildscreen Signaling (WSS), Video Programming System (VPS), and Teletext.