Combined video AGC and digitizing circuit
First Claim
1. A circuit, having an automatic gain control (AGC), for providing a digital output signal having digital values representing analog picture information in an incoming video signal, said incoming video signal also having vertical and horizontal synchronization pulses, said circuit comprising:
- an analog-to-digital converter, having a dynamic range and a certain gain and operative in response to an analog input signal, for producing the digital output signal,means, connected to said converter and operative in response to said incoming video signal and to at least one feedback signal, for producing the analog input signal and for ensuring that picture information contained in said analog input signal consumes substantially all of the dynamic range of the converter,means, operative in response to the occurrence of said synchronization pulses for providing an enable signal and for selectively varying the starting time and duration of the enable signal so as to selectively define an active window, within a video image, on which the AGC is to operate; and
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Abstract
An automatic gain control (AGC) and digitizing circuit, particularly suitable for use in digital video image processing and/or display systems, is disclosed. This circuit advantageously defines an active window within an image area and operates the AGC only on the active window in order to ensure that the active window is always displayed, on a remote monitor, with proper brightness and contrast. The active window can be located anywhere within the image area and can be set to encompass an area extending from only a single picture element to the entire image area.
58 Citations
17 Claims
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1. A circuit, having an automatic gain control (AGC), for providing a digital output signal having digital values representing analog picture information in an incoming video signal, said incoming video signal also having vertical and horizontal synchronization pulses, said circuit comprising:
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an analog-to-digital converter, having a dynamic range and a certain gain and operative in response to an analog input signal, for producing the digital output signal, means, connected to said converter and operative in response to said incoming video signal and to at least one feedback signal, for producing the analog input signal and for ensuring that picture information contained in said analog input signal consumes substantially all of the dynamic range of the converter, means, operative in response to the occurrence of said synchronization pulses for providing an enable signal and for selectively varying the starting time and duration of the enable signal so as to selectively define an active window, within a video image, on which the AGC is to operate; and - View Dependent Claims (3, 5, 7, 9, 11, 17)
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- 2. means, responsive to said digital output signal and to the enable signal, for comparing the digital values against pre-defined minimum and maximum values and, in response thereto, generating said feedback signal.
Specification