Accelerate Equipment Development and Debugging by Using the Capturevu Function of Wfm7100

Users can manually capture video data through menu options, or let the instrument automatically capture a video frame when any video error listed in Table 1 is found. The trigger conditions in Table 1 cover a series of errors in SDI signal format or video signal level.

The user can use the "trigger type" menu to select any of the trigger types supported by the instrument. After configuring the trigger menu, you can set the instrument to the operation mode and wait for any error matching the trigger mode selected by the user for the first time. When an error is found, the waveform monitor will capture the video frame containing the error and store it in the internal memory of the instrument.

Capture of reference samples

The waveform monitor can display the captured data in the waveform window, vector window, color gamut window or image window. In the waveform window (vector window, color window and image window), the captured signal is displayed in yellow trace. The user can observe the captured signal trace alone or compare it with the trace of the current video signal. This is similar to the well-known "freeze" mode used for screen capture. The difference is that after "freezing" the trace or image by screen capture, the instrument cannot create a new display window different from the captured screen image at the same time.

A complete video frame is stored by capturevu technology, so the instrument can reconstruct any display image it supports according to the captured data. For example, suppose that the instrument captures a video frame containing an RGB gamut error, and the instrument initially displays the captured data in the waveform window configured as YPbPr display mode. In order to see the signal components containing color gamut errors, the user may want to view the data in the display window configured for yrgb display mode. At this time, simply change the waveform display mode to yrgb display, and the instrument can automatically create a new waveform display window to display the captured data in yrgb mode. The user can compare it with the current signal in yrgb mode displayed in another window. In addition, the user can also choose to use Tektronix's diamond display to analyze the color gamut error in the captured signal. At this point, the instrument will create a new display for the captured data.

Figure 1 captures an image with RGB gamut error by using the capturevu function of wfm7100.

The user can also use the USB interface on the instrument panel to store the captured video frame data into the USB memory stick. After that, you can also import the data back to this instrument or other instruments from the USB memory stick. For example, after the engineer captures a frame of video data containing errors on site, he can take the data back to the test center to study with his colleagues, while the engineer of the test center can recover the data on another waveform monitor and find problems.

Video format error, manual capture, "gold reference" calibration

As another example, suppose the staff wants to calibrate the camera for the next production. Usually, camera calibration is realized by using a set of camera test charts and measuring the captured signals on the waveform monitor. If a Tektronix monitor with capturevu function is used, after a camera is calibrated, the operator can manually capture a set of video signals with capturevu, and then use the saved data as a "gold reference". The calibration of other cameras can be realized by comparing the display of their shooting signal with the display of the previously saved reference camera shooting signal. Since capturevu uses the original video data to create a display image, the operator can compare the output of the calibrated camera with that of the reference camera through various waveform display, vector display, color gamut display and image display. Moreover, by saving data to the USB memory stick, the operator can also compare the calibration of the camera at different times to check whether the camera performance deteriorates after the use time increases or the conditions in the studio change.

In the design and debugging of video equipment, engineers can use this capture function to diagnose errors in video format. Usually, these error types occur intermittently and may be difficult to separate from the video signal. However, with capturevu, engineers only need to configure the waveform monitor, use the instrument to monitor the video signal and capture the video frame containing errors. After the instrument detects and captures an error frame, the capture time will be recorded in the error log. In this way, engineers can determine whether these errors occur at a fixed time interval when some equipment or other systems in the video signal path change, resulting in changes in the video signal source.

The complete video frame captured by capturevu contains both valid image data and auxiliary data, and these data are stored in a proprietary format on a USB memory stick. Tektronix has developed a set of utilities for this purpose, which can read and format the captured data in the following ways:

• a simple CSV file containing the original CB, y, Cr, y * samples in the captured data. The file cannot be exported directly to spreadsheet software, but it can be used as the input of original text file by user-developed application.

• CSV file optimized for Excel, which can be exported to excel and contains separate samples and line serial numbers.

• *. Pic files that can be used by Tektronix tg700 test signal generator. The data stored in this format can be directly sent to tg700 as a complete image. The file only contains the effective image data required by tg700, and the auxiliary data and blank data are inserted by tg700 module. The utility can be downloaded from the Tektronix website.

When using Excel spreadsheet format, the data appears in the order of CB, y, Cr, y *. Each hexadecimal value is preceded by an "X" prefix, and a header as shown in Table 2 appears at the top of the spreadsheet.

The information provided by the header includes the occurrence time of the captured data, the trigger error type existing in the captured data, and the video signal format. In the example shown in Table 2, the signal is a 1080i59.94 signal containing 1920x1080 effective image area.

In the spreadsheet program, engineers can use various means to classify and search data, or develop visual basic programs to search and format data in a variety of ways. For example, they can find the start point and end point of a valid video in all data (the sequence number is x3ff, x000, x000). Similarly, the engineer can also classify the auxiliary data by finding the data with data patterns of x000, x3ff and x3ff, or finding the data mark (did) specified in the corresponding video standard. Using these tools, engineers can determine whether the auxiliary data sequence output by a specific video device contains errors caused by device code or operation errors.

Observe the artifact noise and test the signal

Usually, engineers test the device under test by measuring the output signal obtained after a test signal passes through the device under test (DUT). With capturevu, you can first capture the video frame of a test signal in the waveform monitor, and then compare it with the field output of the test signal after passing through the DUT to find the difference between the two. The test signals before and after the tested device can be stored in USB memory after being captured. Therefore, engineers can also compare the two files by various means to find the difference between the test signal and the output signal of the tested device.

In the design stage of video equipment, engineers may find it difficult to process a special video sequence or a certain type of image. At this time, they can use capturevu to capture a frame of such video signal, store it in USB memory, and then convert the stored files (*. Cap files) into images (*. Pic files) that can be downloaded to Tektronix tg700. By configuring the test signal generator, the frame image can also be moved horizontally or vertically, so as to generate a moving test image, so as to facilitate the engineer to observe any artifact noise of the equipment product. Since the test signal is converted from the captured video frame at this time, the engineer can still let this known video data source pass through the DUT to compare the difference between the DUT output signal and the original test signal.

Because capturevu has video data capture function, which allows engineers to quickly compare various video signals, it can reduce the time and effort required for video equipment development, installation and maintenance. The ability to reconstruct video data in multiple waveform display windows provides engineers with richer processing means than simple waveform image freezing. At the same time, it also makes it easier for users to determine various problems in video signals. In short, the advantage of capturevu is that it allows engineers to quickly find errors in video signals with simple technical means, so as to help them identify and isolate problems in their equipment or video signal path.