NI TestStand is a test management software designed for the development of automated test applications. Using NI TestStand, you can develop test sequences that integrate code modules written in any test programming language. These sequences also specify execution flow, reporting, database logging, and connectivity to other enterprise systems. You can deploy test programs with user defined operator interfaces. Using the VMS steps for NI TestStand, you can interactively configure your measurements and define pass/fail limit criteria in order to perform various tests on video signals.
To start a video test application in NI TestStand launch the NI TestStand Sequence Editor (Start»All Programs»National Instruments»TestStand»Sequence Editor) and find the NI VMS folder in the Insertion Palette on the left side of the screen. Figure 1 below shows the folder structure for legacy versions of the software. Depending on what is installed, you will see a variety of subfolders for VideoMASTER, VideoMASTER Generation, Digital VideoMASTER, and Digital VideoMASTER Generation. For modern versions of the software, you may see folders for NI PQA, NI AudioMASTER, NI VMS, Analog Video Generator, and Digital Video Generator.
Figure 1. Left - The VideoMASTER Setup step in TestStand can be found in the microLEX folder of the Insertion Palette. Drag and drop the VideoMASTER Setup step into your program to start configuring video tests
Figure 2. Easily change the name of the VMS/VideoMASTER Setup step to fit the measurement
We will now configure our system to acquire the analog video signal we want to test. To start an application, simply right click on the <Insert Steps Here> message in the sequence editor and go to Insert Step»NI VMS»NI VMS Analyzer»NI VMS Analyzer Setup (or Insert Step»microLEX»VideoMASTER»VM Action»VideoMASTER Setup). Another option is to drag a VMS/VideoMASTER Setup step from the Insertion Palette onto the sequence editor. You will insert a new step for every measurement (e.g., colorbar, frequency sweep, multiburst).
The VMS Setup step can be renamed to match the measurement it will make by left clicking the title. To launch the VMS User Interface, right click the step and go to Edit Analyzer. This may take a few moments to load the first time. The VMS Setup step is now ready to be configured for acquisition and performing measurements of the video signal. Tip: If taking several measurements using similar configurations, you can also copy and paste steps within TestStand. By copying and pasting a previously configured NI VMS step, you will reduce the number of configuration changes that need to be made.
Figure 3. The VMS User Interface is where the video signal can be acquired and measurements on the signal can be taken.
The left side of the user interface contains five different tab controls that allow you to configure various parts of your automated test application. These tabs include: File, Analysis, Filter, Sequencer, and Acquisition. The tabs will appear slightly different depending on your version of VMS/VideoMASTER, but their functionality is the same.
Figure 4. The Controls section of the VMS/VideoMASTER User Interface consists of five controls: File Control, Analysis Control, Filter Control, Sequencer Control, and Acquisition Control. These five controls contain all the necessary features to manually test the video signal and take measurements, and also to configure the steps for an automated application.
File Control – The File tab gives you the ability to load previously acquired waveforms and also allows you to save the current waveform to file for offline analysis.
Analysis Control – The Analysis tab is used to configure settings for the measurement to be made (colorbar, multiburst, etc.). The Analysis will be covered extensively in the Performing Measurements section below. This section will be uniquely configured for the given measurement desired in each VMS Setup step.
Filter Control – The Filter tab provides the ability to set software filters on the video signal. Filter classes include: Butterworth, Chebyshev, Inverted Chebyshev, Bessel, Elliptic and FIR. Filtering is activated by selecting a Filter Type different than None on the Filter Control.
Sequencer Control – The Sequencer Control tab defines what information flows between NI TestStand and the VMS Setup step. Depending on your measurement, you may want to send different information to NI TestStand. For example, one test may require the whole waveform to be sent to NI TestStand for reporting purposes, but for most you will probably only pass the specific measurement values.
Another component of the Sequencer tab is the ability to force initialization, acquisition, and closing the hardware connections. For an application that performs multiple measurements, you will only need to initialize your hardware on the first measurement, rather than on each measurement. The Sequencer tab allows you to Force Initialization, Force Acquisition, and Force Close the connection to the hardware in each VMS Setup step. More information on the Sequencer Control will be covered in the Setting Up an Acquisition section below.
Acquisition Control – When preparing an application to acquire the video signal, the hardware settings need to be configured for acquiring the video signal. Settings such as sample rate, video signal type (NTSC, PAL, etc.), input channels, number of lines to read are configured in the Acquisition Control. These settings ensure the VMS Setup step configures the hardware correctly. The Acquisition Control tab will be covered more extensively in the next section.
Figure 5. The Configure button launches a window (right) that shows how the hardware is configured for the acquisition and which channels have an active signal connected.
On the Acquisition tab you will find the Configure and Initialise buttons. Click the Configure button to launch the Hardware Configurator window so you can choose the hardware used for the acquisition. It also indicates which channels have active video signals connected. Clicking the Initialise button launches a window that allows you to initialize the Analog and/or Digital VMS hardware. After the OK button is pressed, the Hardware Initialisation window opens and explains how all the hardware is initialized. Once the hardware is initialized, the Acquire Once and Acquire Continuously buttons will no longer be grayed out in the Acquisition tab.
The Acquire Once button will take a single acquisition of the video signal and update the Waveform graph in the VMS Setup User Interface. Go to the Picture tab and click Refresh and the video display that was captured will be displayed. The Results tab will contain the results of the measurement taken. Taking measurements will be covered in the next section so this tab will be empty until a measurement is configured.
Figure 6. The Waveform and Picture tabs display the video signal acquired.
Automating the Initialization and Acquisition Steps
The configuration and initialization steps can be run manually by pressing the buttons, which is ideal during development and debug of the application to ensure that the VMS Setup step is configured properly. During the automated test this is done programmatically through the Sequencer tab when running the TestStand sequence. Initialization should be configured for the first VMS Setup step in an application and also for any steps that require a change to the signal types (NTSC, PAL, YUV (Component), etc.). By default, the driver will execute an acquisition for each VMS Setup step, but if the acquired video signal from the previous step is valid for the current measurement step, the Force Acquisition should be unchecked to improve test execution time. By initializing and acquiring only when needed, you will significantly reduce the test execution time of your application. For more information on when to force actions, see the NI VMS Help by clicking the ? on the top right hand side of the screen.
Figure 7. The Sequencer tab provides the ability to Force Acquisition, Force Initialization, and Force Closing of the hardware connections. This is extremely beneficial for automated test sequences that contain tens or hundreds of measurements. Tens or hundreds of measurements can be performed in a matter of a seconds, making VMS an ideal solution for automated video test applications.
In order to configure a measurement, there must be a video signal acquired or loaded from file. The measurements are configured in the Analysis tab. The two main parts of the Analysis tab are the Locations File and the Measurement Group.
The Locations File contains information on where in the signal, in time, the measurement should be taken. A Locations File is created for each different video standard (NTSC, PAL, YUV (Component), etc.). For example, the location in the signal that a color bar measurement will be performed on an NTSC signal will be different than the location of the measurement on a PAL signal, so these would have different Locations Files. Several Locations Files are included with VMS for common test patterns and video standards, but you can create user defined Location Files for custom test patterns that fit your specific test requirements.
First select the Locations File to be used by pressing the Select Locations button and choosing the Locations File corresponding to the video standard to be measured. Next, ensure that the Locations File configuration complies with the video waveform being measured. Click the Edit Locations button to launch the Measurement Locations Editor window. If the Edit Locations button is disabled, it means no signal has been acquired yet and an acquisition is needed.
Figure 8. For the ColorBar Measurement, the three locations that must be set are the where the white starts, where the color starts, and where the color ends. These can be chosen by moving the cursor on the graph to that location of the signal.
At the bottom of the Measurement Locations Editor there is a tab for each measured test element in the video signal (Color Bars, Color Multiburst, Bar, etc.). Information on making edits to each of these locations can be found in the NI VMS Help under NI VMS Interfaces»Measurement Locations Editor. Once the locations have been verified, press the Close button to exit the Edit Locations window.
The measurement can be tested manually by clicking the Measure Once button on the Analysis tab. The Results tab will then populate for the measurement specified. The information from the Measurement Results section of the Results tab is also passed to TestStand where it can then be evaluated to see if the system meets requirements.
Figure 9. The Results tab contains all the relevant results from the measurement performed on the video signal.
In order for a video test system to pass the automated test sequence, the individual tests must be compared to company or industry standards and requirements. This is accomplished for each measurement using the Limit Editor.
To launch the Limit Editor, click on the VMS Setup step in the sequence editor of TestStand. At the bottom of the screen you will see an Edit Limits button. This will launch the Limits Editor and allow you to change limits for that test. Another option is to right click on the VMS Setup step and go to Edit Limits.
Figure 10. The Limits Editor is launched from the TestStand sequence editor and is used to compare the VMS measurement results with internal requirements or industry standards.
The scroll bar on the left side of the window scrolls through all the measurement results that can be evaluated. The Minimum Limit and Maximum Limit columns can be edited to ensure the measurements meet requirements.
The defined set of limits will be saved with the NI TestStand sequence file. However, the limits can also be saved to file and then reused in other test applications. For example a company may define its limits for general types of products. When developing a new test application, you can load the limits from a file that already exists. The Limit Editor also has the ability to dynamically load limits, allowing you to dynamically load limits from file.
Developing an automated video test application combines the previous sections into a single application. For this example, an application will be set up to automate the testing of an NTSC signal that has a test matrix that consists of a colorbar (test lines 0-130) and a multiburst signal (test lines 131-261).
Figure 11. The test matrix being generated can contain several patterns that need to be measured against internal and industry standards
In this example, there are two test patterns that will be measured and tested. The first part is to insert two VMS Setup steps into the TestStand Sequence Editor. These can renamed to Colorbar and Multiburst to fit the measurement they will perform.
Next, the first VMS Setup step (Colorbar) User Interface should be opened and configured for the measurement and the hardware should be initialized. Open the VMS User interface for the first measurement and go to the Acquisition tab. Choose NTSC for the signal type and Port 1 for the signal (the signal is connected to Channel 0 of the digitizer), then click the Initialise button and choose ANALOGUE – including Digitiser… Since this is the first measurement being made, the hardware must be programmatically initialized, so the Force Initialise and Force Acquire boxes on the Sequencer tab must now be checked.
Now that the hardware is configured and a signal has been acquired the measurement can be configured. Note, you must manually acquire the signal once to set up the Analysis tab. Go to the Analysis tab and select the NTSC –TPG Locations File, since this is an NTSC signal. Enter the line number that will be measured below the Waveform Graph (any line from 21-131 will work). Choose the Color Bar measurement, and click Edit Locations to verify the locations file is configured correctly. Click the Colour Bars tab and go through the Update from Curser list to ensure that the locations for start white, start of color, and end of color are correct. When finished, click Close. Click OK to exit the Colorbar measurement step.
The next step is to configure the Multiburst measurement step. Open the VMS User Interface for the Multiburst measurement step. Since the hardware was initialized in the first step, you can uncheck the Force Initialise and Force Acquire boxes on the Sequencer tab. Go to the Analysis tab to choose the Multiburst measurement setting and choose the measurement line (any line 131-262 will work). After taking another manual acquisition of the signal go to click on Edit Locations and ensure that each section of the Update from Curser list is correctly configured. When finished, click Close. Click OK to exit the Multiburst measurement step.
In TestStand, open the Limits Editor for Colorbar measurement step and make the lower limit for the White Luminance Amplitude 700 mV and the upper amplitude 800 mV. Click OK to exit the Limits Editor. Open the Limits Editor for the Multiburst measurement step and change the Burst 1 Amplitude lower limit to 400 mV and the upper limit to 420 mV. Click OK to exit the Limits Editor.
Figure 12. The Run UUTs button will run the automated video test application.
Click on Run UUTs in the TestStand menu and the automated test will run and show whether the system passed or failed within seconds. A report is also generated of all the measurements taken and which tests passed or failed.
The ability to quickly configure a set of tests to evaluate the quality of a video signal combined with the ease of automation of NI VMS is making video test much easier for engineers throughout the industry. The combination of faster test times with faster development times makes NI VMS a powerful solution for video test.
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