Testing Analog and Digital Video with LabVIEW and PXI
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Figure 1. PXI provides a modular, mixed-signal platform for testing both analog and digital video signals in a single system.
There seems to be no end to the list of video technologies that are constantly emerging for the latest consumer electronic devices – Blu-ray Disc, HD DVD, 1080p, High-Definition Multimedia Interface (HDMI), Digital Visual Interface (DVI), S-Video, and component video to name a few. The explosion in video standards over the last few years has left manufacturers struggling to find end-of-line functional video test solutions that can keep up with new video standards while meeting aggressive time-to-market and price targets.
In addition to basic compliance testing, manufacturers use functional video testing to verify the quality of video signals displayed or generated by a device following assembly. The modular nature of PXI, combined with mixed-signal instrumentation, makes it an ideal platform for testing both analog and digital video in a single system, capable of expanding channel count or adapting as standards evolve. Engineers can quickly take custom measurements on video signals using NI LabVIEW software or manipulate data through the NI Vision Development Module and other LabVIEW toolkits.
Analog video standards include composite and RGB component video in both standard and high-definition formats. Acquiring these signals with PXI requires high-resolution digitizers to accurately capture the analog signal. With up to 14 bits of resolution and advanced video triggering to detect valid signals, a digitizer can analyze color burst or measure chrominance and luminance values. The analysis is typically performed on a single frame from a known test image, such as a color bar or other predefined pattern.
Digital video offers a cleaner signal with less noise and higher bandwidth through compression algorithms. DVI and HDMI are the two dominant digital video standards, which can be captured or generated with PXI digital instrumentation up to 100 MHz for resolutions as high as 1080i. Digital video test measures similar parameters to analog test, and it may also include bit error rate (BER) testing to compare individual bits, pixel by pixel, against a known good template.
Manufacturers often want to stream multiple frames of video to look for other imperfections such as MPEG compression artifacts or other bit errors introduced by processing from DSPs. PXI Express digitizers, arbitrary waveform generators, and high-speed digital instruments offer increased bandwidth to record or play back high-resolution video to or from external RAID storage solutions.
Developing algorithms to analyze analog and digital video is not a trivial task. National Instruments Alliance Partner microLEX Systems A/S offers VideoMASTER, a functional video test suite based on LabVIEW that uses PXI to test analog and digital video resolutions up to 1080i. VideoMASTER tests a variety of functional video measurements on a product to determine whether it passes or fails signal quality. DAQTron, another NI Alliance Partner, also offers a video test suite for high-definition broadcast video signals including DVB, ATSC, and ISDB-T. The solutions from microLEX and DAQTron for acquiring or generating video test patterns are based on PXI modular instruments from NI and offer connectivity options for any video standard including composite, component, S-Video, and HDMI.
Table 2. NI offers a variety of PXI products for acquiring and generating video signals with resolutions of up to 1080i.
Learn more about analog and digital video testing with PXI instruments.
This article first appeared in the Q1 2008 issue of Instrumentation Newsletter.
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