An automated system for verifying digital video signal parameters based on NIPXI

challenge:

Develop a Manufacturing Test System (MTS) that can test wireless HDMI multiple-input multiple-output (MIMO) products according to current industry standards and eliminate the need for human intervention in determining the quality of video transmissions.

Solution:

Using NIPXI, NIVideoMASTER, NILabVIEW, and NITestStand management software, develop an automated system for validating digital video signal parameters, ranging from channel delay measurements and color verification to sync pulse timing, noise spectrum, and nonlinear measurements.

"Using a common software platform based on NI TestStand software, Benetel has essentially cut new project development time by 75 percent and is making it easier to produce high-quality, high-reliability end products."

Benetel has extensive experience in RF and wireless design and test systems. We are committed to providing high-quality, high-performance products to customers from all walks of life around the world. Digital video testing occupies a large part of our business scope, and we need a flexible, adaptable, and fully upgraded test system to support some wireless digital video streaming products.

Our application requires a manufacturing test system (MTS) to test the transmission unit and the receiving unit. The transmission unit is based on wireless media and modulates and transmits downstream high-definition video and audio content through a multiple-input and multiple-output configuration of multiple wireless output channels and low-rate data output wireless channels.

The receiving unit receives wireless high-definition video content and demodulates the video content using a multiple-input multiple-output configuration of multiple wireless data channels and low-rate channels that generate uplink channels for data content transmission, reproducing video, audio and control information. The output of the receiving unit is digital uncompressed video, digital audio and control information, all of which are output through the HDMI connector.

We will build the test system software based on Benetel's Universal Test Platform, a powerful, flexible software core based on NI TestStand software and LabVIEW software that actively supports applications requiring multithreading, database connectivity, and test fixture control.

We will build the test system hardware based on the NIPXI system of NIVideoMASTER hardware, which consists of the NIPXI-6542 digital video generator and logic analyzer module, and also supports various modules such as the NIPXI-5122 high-speed digital analyzer, NIPXI RF signal generator and NIPXI-8430 serial interface module. We route the signals through high-quality cables and connect them to a pair of TX (transmit) and RX (receive) protective shields, which is very necessary for over-the-air testing based on unit testing.

We can use the manufacturing test system to test the UUTs in TX and RX independently. This parallel testing approach forms a core part of Benetel's production test strategy and greatly improves overall throughput. The use of the automatic scheduling function in NI's TestStand software also improves the efficiency of test operations by automatically scheduling the execution order of parallel tests, reducing test consumption time and increasing resource utilization.

We use manufacturing test systems to analyze a wide range of wireless video signals at 720i/p and 1080i/p resolutions at any RF frequency, including 5.8 and 60GHz. We configure the test system with many features, from logging serial numbers, configurations, and software versions to video and audio tests such as horizontal timing, channel delay, color bars, K-factor, noise spectrum, distortion, and multiburst testing. The system also includes a high-rate automated implementation of a peak signal-to-noise ratio (PSNR) algorithm, which we also use as an approximation of human perception of image reconstruction quality to verify the quality of transmitted video images.

A major production requirement for testing wireless and other video signals is verification of the quality of transmitted video and audio. Historically, video quality verification has been a subjective science. Efforts to automate this particular test requirement have continued to rely on manual intervention with a noticeable effect on throughput to maintain quality at an acceptable level. Using NIVideoMASTER to objectively quantify and measure a large number of peak signal-to-noise ratio digital signal parameters, we have greatly increased our confidence in achieving video signal quality while maintaining high throughput.

In addition to video quality, manufacturing test systems also measure parameters such as audio quality, receive signal strength, and upstream information. These test requirements take advantage of the serial interface tools and string processing capabilities of LabVIEW and NI TestStand software to quickly and reliably parse data to and from the UUT.

Benefits of Using NI Tools

We use a PXI-based system that integrates all modular system requirements into a single installation package. The combination of PXI drivers with a relatively low development budget and widely available LabVIEW built-in tools and toolboxes creates a cost-effective system compared to other approaches. We can also benefit from effective after-sales support from NI. In addition, the NI VideoMASTER PXI-6542 digital video generator can easily interact with the Benetel universal test platform, allowing the use of dedicated test modes, so that we can develop a single mode to combine all components together, which is very necessary for any video or image test application. By reducing the need to switch between test modes, thereby reducing the number of samples required, the NI VideoMASTER generator can save a lot of test time from the overall test time. [page]

Figure 1: Benetel console

Figure 2: Wireless HDMI digital video test system block diagram

Figure 3: Test pattern used in peak signal-to-noise ratio testing