Video Signal Processing ( 39 ) :

Video mixers and effects

• Video Effects Unit - unit provides various wipe patterns for use when video dubbing, wipes one signal to black, it does not provide mixing between two separate input signals   

Computer video generation circuits

• A Simple VGA Controller for the ALTERA UP1 Board - VGA signal generation using FPGA   
• Generator of videosignal for VGA monitor on PIC16x84 - This is an adaptation of a scheme, designed by Eric Schlaepfer, widespreads in the Internet. This scheme is very simple also contains a minimum of units, is hooked up directly to VGA to the videoconnector. Will be used PIC16x84 with a crystal frequency 4Mhz.   
• SVGA Generator - circuit to generate SVGA mode video 640x480..1024x768, based on Altera CPLD, text in German   
• VGA Generato - VGA 640x480 test picture generator based on PIC12C509A   
• VGA Signal Generation with the XS Board - How to generate simple VGA monitor signals using Xilinx FPGA   

Video overlay

• Video Clock Superimposer - This circuit superimposes the time of day in the bottom right-hand corner of an existing video signal, based on PIC16C711   

Digital video technology

• 24-bit RGB Video Digitizer - designed for use as the front end of a digital video processor   
• Amiga Frame Grabber Documentation - This document describes the hardware and software for an Amiga based video digitizing system.   
• Closed-Caption Decoder with serial output - based on a PIC16C71, an �lantec EL4581C sync separator, and an LM393 dual comparator   
• Dirt Cheap Frame Grabber V2.02 - This is a very cheap and simple but bad quality video digitizer for PC. The purpose of the DCFG is to simply provide a very simple method to grab video pictures and display them on a computer monitor. The DCFG requires at least a 80286 or better and a VGA display to run.   
• Homebuilt Video digitiser Mk1 - A "video-digitiser" captures television pictures from a TV set, camera, or video recorder, etc., and forwards them to a computer for display, storage, or general manipulation. This document describes a home-built digitiser which interfaces to an EPP (or bi-directional) parallel port on IBM PCs.   
• Homebuilt Video digitiser Mk2 - A "video-digitiser" captures still frames from a TV set, video camera, or video recorder, etc., and forwards them to a computer for display, storage, or general manipulation. This document describes the MarkII version of a home-built digitiser which interfaces to an EPP parallel port on IBM PCs. MkII supports colour captures (PAL/NTSC decoding in software).   
• Homebuilt digital video TBC/standards converter - This project is a timebase corrector/standards converter. There is only a partial projecgt description available.   
• Software-based PAL colour decoding - This page explains the issues concerning the decoding of colour from broadcast-standard television pictures, and presents software algorithms and a Windows-based application capable of colourising digitized PAL-encoded still-frame images with very high quality. This is an interesting project in practical image-processing!   

Video measurements

• Trigger circuit locks onto one horizontal line - produces an oscilloscope trigger that synchronizes the horizontal sweep to a video signal that allows you to view any horizontal line by adjusting a potentiometer   
• Video Line Sync Trigger Generator - trigger your oscilloscope on specific lines in a video signal   

Video circuit design tips

• Active filters for video meet antialiasing and reconstruction requirements - Original video filters were passive L-C circuits surrounded by amplifiers. Today, you can achieve smaller and more efficient designs by combining the amplifier with an R-C filter. Moreover, sensitivity analysis and predistortion methods have overcome the poor performance that gave early video filters a bad reputation.   
• Black Level Clamp for video signals - proper video signal clamping is very interesting subject   
• Composite Video (NTSC/PAL) to RGB   
• Inverting an Analog Video Signal - it is not totally trivial   
• S-Video to Composite    Rate this link
• Sync Generators and Separators   
• Video Cables   
• Video: Selecting Filter Transfer Functions - to design a superior video processing system, you must choose the right type of filter transfer function for the application   

Combining many signals to one cable

• Camera power and video use same coax cable - It is convenient to run both the power and the video signal through one coax cable but it needs some extra electronics on both ends of the coaxial cable. The circuitry at the monitor end of the coax cable supplies all the power to the coaxial cable with 24V through a gyrator circuit. The camera end uses a 12V fixed-voltage regulator to supply 12V to a CCD video camera. A driving transistor on camera end modulates the video on the 20V-dc line.   
• Single Coax Carries Video, Power, and Channel-Select Signals - This is and interresting application note in pdf format.   

TV antenna circuits

• TV antenna amplifier - covers the frequencies from 40 to 900 MHz, suitable frequency rage for FM or TV antenna amplifier   
• UHF-TV Booster - This is a UHF-band TV pre-amplifier which uses special HF transistors , BFQ85 or BFR90.   

Misc circuits

• Adjustable LNB Power Supply Is DiSEqC Compatible - This circuit provides a digitally switchable 13V or 17V for the low-noise block (LNB) typically found in satellite receivers at the antenna feedhorn. This variation of supply voltage "tells" the remotely located LNB electronics whether it should set the antenna polarization clockwise or counterclockwise, which thereby eliminates the need for an interface and cable connection to the antenna. The circuit shown also supports an emerging and more sophisticated communications bus called the DiSEqC standard (for Digital Satellite Equipment Control).   
• Closed-Caption Decoder - This is a closed-caption decoder with serial output, based on a PIC16C71, an �lantec EL4581C sync separator, and an LM393 dual comparator (for data slicing with automatic threshold).   
• High Gain Video Amplifier - This circuit from Maxim application note provides 40 dB amplification with 10 MHz bandwidth.   
• Maxim Video Circuits application notes   
• Old LCD projector To LCD Display - The old LCD projectors were made to work with overhead displays. Basically, they were clear panels and you would have to provide some bright source of light behind them, so they would "project" their image on a wall.
• PI6ATV circuits - video switchers, modulators and signal generators for amateur TV   
• Single Coax Carries Video, Power, and Channel-Select Signals - This is and interresting application note in pdf format.   
• The KD2BD Video Operated Relay - turns on relay if there is video signal present in the input   
• TV-Out Connection with CRT Discharge Protection - how to protect video outputs of sensitive ICs, pdf file   
• Applying the ML6431 Video Genlock Using the ML6430/ML6431 Evaluation Kit - The ML6430/6431 Evaluation Board contains a single package IC Genlock capable of correcting for VCR glitches and head switching, tape dropouts, missing sync pulses, freeze frames, high speed playback, and camcorder gyro errors. It also generates sampling frequencies for video and audio along with signals for both horizontal and vertical signal processing. All of this is available in PAL, NTSC, and some VGA formats. The ML6431 differs from the ML6430 in its internal register structures. This is really for VCRs with "dropped" syncs. The colour subcarrier is defined by a crystal.

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