Creating a Wireless HDMI MIMO Digital Video Test System Using NI Video Measurement Suite and PXI

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"Using a common software platform based on NI TestStand allows Benetel to radically cut development time on new projects by up to 75 percent and facilitates delivery of a high-quality, proven end product."

- Darragh McShane, Benetel

The Challenge:
Developing a manufacturing test system (MTS) capable of testing a wireless HDMI multiple input, multiple output (MIMO) product to current industry standards, and removing the requirement for human intervention in determining video transmission quality.

The Solution:
Using an NI PXI solution in tandem with NI Video Measurement Suite, LabVIEW, and NI TestStand to develop an automated system to verify digital video signal parameters ranging from channel delay measurements and colour verification to synchronisation pulse timing, noise spectrum, and nonlinearity measurements.

Author(s):
Darragh McShane - Benetel

Benetel has extensive experience in RF and wireless design and test system design and we focus on delivering quality, high-performance products to a global customer base across a range of industries and applications. Digital video testing represents a growing area of our business that demands a flexible, adaptable, and fully upgradable test system to support a range of wireless digital video streaming products.

Our application required an MTS to test a transmission unit and receive unit. The transmission unit modulates and transmits downstream HD video and audio content over a wireless medium using a MIMO configuration of multiple wireless output channels and a low-rate data input wireless channel.

The receive unit receives the wireless HD content, demodulates it, and regenerates the video, audio, and control content using a MIMO configuration of multiple wireless data channels and a low-rate control channel, which generates an upstream channel for data content transmissions. The receiver unit outputs are digital uncompressed video and digital audio and control, all output via an HDMI connector.

We based the MTS software on Benetel’s Common Test Platform, which is a powerful, flexible software core based on NI TestStand and LabVIEW software with active support for applications requiring multithreading, database connectivity, and test fixture control.

We based the MTS hardware around an NI PXI system using NI Video Measurement Suite hardware, which consists of NI PXI-6542 digital video generator and analyzer modules, as well as support modules such as the NI PXI-5122 high-speed digitizer, an NI PXI RF signal generator, and a NI PXI-8430 serial interface module. We routed the signals via premium-quality HDMI cables to a pair of TX (transmit) and RX (receive) shielded fixture enclosures, which are necessary to facilitate over-the-air testing of the unit under test (UUT).

We can independently test TX and RX UUTs with the MTS. This parallel test approach, which forms a core part of Benetel’s production test strategy, greatly increases overall throughput. Using NI TestStand autoscheduling also increases testing operations efficiency by automatically scheduling parallel test execution order, minimising test time and maximising resource usage.

We used the MTS to analyse a range of wireless video signals including 720i/p and 1080i/p resolutions at any RF frequency, including 5.8  and 60 GHz. We configured the test system for many functions, from recording serial numbers, configuration, and software versions to video and audio tests such as horizontal timing, channel delay, colour bars, k factor, noise spectrum, distortion, and multiburst testing. It also contains a high-speed automated implementation of the peak signal-to-noise ratio (PSNR) algorithm, which we used as an approximation of human perception of image reconstruction quality to verify the video image quality following transmission.

The main production testing requirement for wireless and other video signals is transmitted video and audio signal quality verification. Historically, video quality verification has been a subjective science. Previous attempts to automate this particular test requirement continued to rely on human intervention to maintain an acceptable level of quality with an obvious detrimental effect on throughput. Using NI Video Measurement Suite to objectively quantify and measure a range of digital signal parameters in tandem with PSNR, we achieved a significantly increased level of confidence in the video signal quality while maintaining high throughput.

In addition to video quality, the MTS measures parameters such as audio quality, received signal strength, and upstream messaging. These test requirements take advantage of LabVIEW and NI TestStand serial interfacing tools and string processing functions to parse data to and from the UUT quickly and reliably.

Benefits of Using NI Tools

We used a PXI-based system to incorporate all of our diverse modular system requirements in one rack-mountable package. The relatively low development overhead associated with PXI drivers coupled with the widespread availability of LabVIEW built-in tools and toolkits led to a highly cost-effective system when compared to any alternative method. We also benefited from effective after-sales support from NI. Furthermore, the NI Video Measurement Suite PXI-6542 digital video generator easily interfaces with Benetel’s Common Test Platform and introduces the possibility of using proprietary test patterns, which we could use to develop a single pattern incorporating all the components necessary for any particular video or image testing application. By reducing the need to switch between test patterns, and hence reducing the number of acquisitions required, the NI Video Measurement Suite generator offers significant savings in terms of overall test time.

Author Information:
Darragh McShane
Benetel
Ireland
darraghmcshane@benetel.com

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