A method and a circuit for deriving a synchronisation signal from a video signal

A technology of video signal and synchronous signal, which is applied in parts of color TV, parts of TV system, TV, etc.

Inactive Publication Date: 2010-12-08
ANALOG DEVICES INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, Bohm's method requires that the sync spike level of the horizontal sync signal of the input video signal should be within a relatively narrow range
Therefore, Bohm's method is not suitable for situations where the amplitude of the horizontal synchronization signal varies greatly

Method used

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  • A method and a circuit for deriving a synchronisation signal from a video signal
  • A method and a circuit for deriving a synchronisation signal from a video signal
  • A method and a circuit for deriving a synchronisation signal from a video signal

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Embodiment Construction

[0092] Figures 10A-10C is a flowchart representing method steps performed by a method for deriving a synchronization signal from a video signal according to another embodiment of the present invention.

[0093] Figure 10D show how to combine Figures 10A-10C process.

[0094] See attached drawings, see first Figures 1 to 4 , represents a decoder for decoding video signals according to the present invention, the whole of which is indicated by index number 1 . The decoder 1 comprises an effective signal processing and decoding circuit, generally indicated by index number 2, and a sync pulse signal recovery circuit, also in accordance with the invention, generally indicated by index number 3, for implementing a A method for deriving a synchronization signal from a video signal from which a horizontal synchronization signal of the video signal and, in turn, a vertical synchronization signal and a field signal are also recoverable. A synchronous signal recovery circuit 3 is...

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Abstract

A method for deriving a synchronisation signal (35) from a video signal comprises tracking the blanking level (107) of the video signal with first and second slice level signals (26, 27) and tracking the sync tip level (110) of the horizontal sync signal (109) of the video signal with third and fourth slice level signals (28, 29) for determining the blanking level (107) and the sync tip level (110). A value for an intermediate slice level signal (30) is computed from the first, second, third and fourth slice level signals (26, 27, 28, 29) so that the value of the intermediate slice level signal (30) lies approximately halfway between the blanking level (107) and the sync tip level (110). The video signal is compared with the intermediate slice level signal (30), and the synchronisation signal (35) is prepared from a logic signal by transitioning the logic signal from one of the logic high and logic low levels to the other of the logic high and logic low levels, each time the video signal transitions across the intermediate slice level signal (30).

Description

technical field [0001] The present invention relates to a method and a circuit for deriving a synchronization signal from a video signal and, in particular, to a method and a circuit for deriving a synchronization signal from a video signal allowing the horizontal synchronization signal to be recovered from the video signal. Background technique [0002] Methods and circuits for recovering synchronization signals from video signals are known. This method and circuit can be modified to recover the synchronization signal sequentially or simultaneously with efficient processing and decoding of the video signal. However, the complete recovery of the sync signal sequentially with efficient processing and decoding of the video signal generally prevents fast synchronization of the video signal. Therefore, in order to minimize synchronization time, it is known to pass the video signal in parallel through two circuits, one of which performs efficient signal processing and decoding o...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04N5/08H04N5/10H04N5/16
CPCH04N5/10H04N5/08H04N5/16
Inventor 尼尔·D.·奥康奈尔
Owner ANALOG DEVICES INC
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