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This tutorial is part of the NI Analog Resource Center. Each tutorial will teach you a specific topic by explaining the theory and giving practical examples. This tutorial quickly introduces the basics of video testing and provides an example solution.
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Table of Contents
Understanding Composite Video Signals
A composite video signal is a signal in which all the components required to generate a video signal are embedded in a single signal. The three main components that together form a composite signal are as follows:
- The luma signal (or luminance)-Contains the intensity (brightness or darkness) information of the video image
- The chroma signal-Contains the color information of the video image
- The synchronization signal-Controls the scanning of the signal on a display such as the TV screen
The monochrome composite signal is built of two components: luma (or luminance) and synchronization. This signal, which is usually called the Y signal, is shown in Figure 1.
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Figure 1. Monochrome Composite Video Signal (Luma Steps from White to Black)
The chroma signal by itself, which is usually called the C signal, is shown in Figure 2.
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Figure 2. Color Information Signal for a Color Bar Line (Including the Color Burst)
The composite color video signal, often called the Color Video, Blank, and Sync (CVBS) signal, is the sum of Y and C , is shown in Figure 3.
CVBS = Y + C
The two components Y and C can also be distributed separately as two independent signals. These two signals together are called either Y/C or S-video.
Example Test System Configuration
A common device under test (DUT) is a video switch. To test this type of DUT, you need to generate a color bar pattern and pass it through the video switch. Then the test system will acquire the signal from switch and perform numerous video signal measurements and compare it to the standard limits. An example of the test system is shown in figure 4.
Figure 4. Example Test Configuration
The measurements can be made with the following hardware and software products, as shown in figure 5:
- NI PXI-5421 100MS/s 16-bit Arb
- NI PXI-5122 100MS/s, 100MHz 14-bit Digitizer
- VideoMASTER Product from microLEX
- NI TestStand Test Management Software
Figure 5. Example PXI System
MicroLex VideoMASTER Solution
The MicroLEX VideoMaster is a video analyzer tool suite for analog video signals, Composite video, S- Video and Component video (HDTV and SDTV). VideoMASTER employs a digitizer, the National instruments PXI-5122, a 14-bit, 100 MS/s, two channel with built in triggering for Composite and S-video. Combined with highly efficient software tools, a range of scalable solutions for analog video analysis and production test of analog video signals is available:
- Composite video
- S-Video & Composite video
- Component video (HDTV, SDTV), S-video & Composite video
The top-end version of the analog VideoMASTER range of solutions (Component, S-video and Composite) requires additional RF switching, HDTV triggering and control, cable breakout box, etc. in addition to the PXI-5122 digitizer. All of this is included in the solution for the top-end model. The two other models only require the digitizer and some cable accessories, all of which is included in the bundled solution. The VideoMASTER consists of scalable solutions that can be upgraded. A user, which may have started with a Composite video testing solution, can upgrade the system, if needs are changing at a later point in time. That reduces risks and keeps the investment budget at a minimum but still retaining the flexible of advancing the test solution at a later stage.
Figure 6. Example of MicroLEX VideoMaster Solution
The high accuracy of the digitizer, combined with advanced software measurement algorithms ensures an easy-to-use and highly flexible approach to video-testing at a very competitive cost. The VideoMASTER software is based on LabVIEW. These LabVIEW toolsets can be integrated into test sequencers like TestStand. VideoMASTER also available as high level LabVIEW Express VIs.
Figure 7. Tight Integration of VideoMASTER and NI TestStand
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