Multiplexed video signal interface signal, system and method

• US 6,650,371 B1
• Filed: 06/22/2000
• Issued: 11/18/2003
• Est. Priority Date: 09/09/1999
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Hojabri, Peyman, Morrish, Andrew
• Primary Examiner(s): LEE, MICHAEL
• Application Number:
  US09/602,175
• Time in Patent Office: 1,244 Days
• Field of Search: H04/N.550, H04/N.5202, 348/569, 348/564, 348/565, 348/678, 348/679, 348/680, 348/687, 348/563, 348/467, 348/468, 348/473, 348/474, 348/476, 348/477, 348/588, 348/589, 348/379, 345/2.1, 345/2.2, 315/383
• US Class Current: 348/569
• CPC Class Codes: H04N 5/57 Control of contrast or brightness

Abstract

A multiplexed video signal interface in accordance with the present invention provides a multiplexed component video signal in which, in addition to the component video signals with OSD data and user-controllable contrast and video gain, includes control signal components for image brightness and CRT bias along with the ability to individually control such control signal components. This advantageously minimizes the complexity of the necessary signal interfaces and allows for greater integration of circuit functions, thereby significantly reducing circuit complexity, size and costs.

Claims

1. An apparatus including a signal multiplexor for multiplexing video image, on-screen-display (OSD) and display control signals, comprising:

a first control circuit that upon receiving a reference signal, a contrast control signal and a clamped video signal provides a first controlled signal with a contrast-controlled video component;

a first signal combining circuit, coupled to said first control circuit, that in response to a first combining control signal receives and selectively combines an OSD signal and said first controlled signal to thereby provide a first combination signal with said contrast-controlled video component and an OSD component;

a second control circuit, coupled to said first signal combining circuit, that upon receiving said first combination signal, said reference signal and a gain control signal provides a second controlled signal with a contrast-controlled and gain-controlled video component and a gain controlled OSD component;

a third control circuit that upon receiving and combining a brightness control signal and a bias control signal and receiving said gain control signal provides a third controlled signal with a gain-controlled brightness control component and a bias control component; and

a second signal combining circuit, coupled to said second control circuit and said third control circuit, that in response to a second combining control signal receives and selectively combines said second and third controlled signals to thereby provide a multiplexed signal with said contrast-controlled and gain-controlled video component, said gain-controlled OSD component, said gain-controlled brightness control component and said bias control component.

2. The apparatus of claim 1, further comprising a clamp circuit, coupled to said first control circuit, that upon receiving said reference signal, a clamp control signal, said first controlled signal and an input video signal provides said clamped video signal.

3. The apparatus of claim 2, wherein said clamp circuit comprises:

an input stage that upon receiving and combining a switched clamp signal and said input video signal provides said clamped video signal;

a comparator circuit, coupled to said first control circuit, that upon receiving and comparing said reference signal and said first controlled signal provides a clamp signal; and

a switch circuit, coupled between said comparator circuit and said input stage, that in response to said clamp control signal receives and switches said clamp signal to thereby provide said switched clamp signal.

4. The apparatus of claim 1, wherein said first signal combining circuit comprises a multiplexor circuit that multiplexes said OSD signal and said first controlled signal in response to said first combining control signal to thereby provide said first combination signal.

5. The apparatus of claim 1, wherein said third control circuit comprises:

a first conversion circuit that upon receiving and converting said brightness control signal provides a first analog signal;

a second conversion circuit that upon receiving and converting said bias control signal provides a second analog signal; and

a controllable gain circuit, coupled between said fast and second conversion circuits and said second signal combining circuit, that in response to said gain control signal receives and combines said first and second analog signals to thereby provide said third controlled signal.

6. The apparatus of claim 5, wherein said first and second conversion circuits comprise first and second digital-to-analog conversion circuits.

7. The apparatus of claim 1, wherein said third control circuit comprises:

a first conversion circuit that upon receiving and converting said brightness control signal provides a first analog signal;

a second conversion circuit that upon receiving and converting said bias control signal provides a second analog signal;

a third signal combining circuit, coupled between said first and second conversion circuits, that upon receiving and combining said first and second analog signals provides a third analog signal; and

a controllable gain circuit, coupled between said third signal combining circuit, said second conversion circuit and said second signal combining circuit, that in response to said gain control signal receives and combines said third and second analog signals to thereby provide said third controlled signal.

8. The apparatus of claim 7, wherein:

said first and second conversion circuits comprise first and second digital-to-analog conversion circuits; and

said third signal combining circuit comprises a signal summing circuit.

9. The apparatus of claim 1, wherein said second signal combining circuit comprises a multiplexor circuit that multiplexes said second and third controlled signals in response to said second combining control signal to thereby provide said multiplexed signal.

10. A method of multiplexing video image, on-screen-display (OSD) and display control signals, comprising the steps of:

receiving a reference signal, a contrast control signal and a clamped video signal and in response thereto generating a first controlled signal with a contrast-controlled video component;

receiving a fat combining control signal and in response thereto receiving and selectively combining an OSD signal and said first controlled signal and thereby generating a first combination signal with said contrast-controlled video component and an OSD component;

receiving said first combination signal, said reference signal and a gain control signal and in response thereto generating a second controlled signal with a contrast-controlled and gain-controlled video component and a gain-controlled OSD component;

receiving and combining a brightness control signal and a bias control signal and receiving said gain control signal and in response thereto generating a third controlled signal with a gain-controlled brightness control component and a bias control component; and

receiving a second combining control signal and in response thereto receiving and selectively combining said second and third controlled signals and thereby generating a multiplexed signal with said contrast-controlled and gain-controlled video component, said gain-controlled OSD component, said gain-controlled brightness control component and said bias control component.