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The addition of high-definition video technology to mobile devices such as smartphones, personal digital assistants (PDAs), gaming consoles, camcorders, and digital cameras is transforming the way consumers capture and share the world around them. These devices include their own OSs, wireless protocols, and I/O points, making it even more challenging for engineers to develop comprehensive test suites for mobile devices while maintaining the test speeds required for profit goals.
This tutorial explores how you can take advantage of high-performance PXI-based modular instruments to drastically reduce the cost of testing mobile devices. The tutorial focuses on testing the audio and video interfaces of the products, but with the PXI platform, you can easily customize your solution to also test the wireless standards, digital signal processors (DSPs), or power consumption. To learn more about testing these aspects, visit ni.com/semiconductor or ni.com/rf.
Table of Contents
Physical Layer versus Functional Test
Test strategies for mobile devices such as cell phones or camcorders are different in design than in production test. In design, physical layer testing of the bit error rate (BER), jitter, and eye diagram of the video signal ensures the video chip implementation is working to specification. During validation and production test, the focus is on the functional test of the system. Is each of the video interfaces working properly? Did the encoder/decoder cause lossy data? Is the HDMI output really generating 1080p/60 Hz video? Is the screen resolution correct when connecting the camcorder to a 1920 x 1080 LCD? What about a 1400 x 1080 LCD? Throughout validation and production, you must answer these questions and more not only in detail but also as fast as possible to get the product to market quickly.
Physical layer tests such as BER or eye diagram evaluation do not ensure that the resulting video contains the correct timing parameters, color levels, and gain parameters that are essential to providing the highest-quality product to customers. For this reason, it is important to perform a functional evaluation of the mobile device.
Functional Video Test for Validation and Production
To better understand the different functional tests required, consider the different audio and video interfaces on a common mobile device.
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Figure 1. Mobile devices such as cell phones and camcorders often have multiple audio and video interfaces that must be tested. Exhaustive testing of these interfaces is a key challenge when trying to get the device into customers’ hands as quickly as possible. |
Testing the LCD display typically requires a video generator to generate a known video source through the internal video circuit and pixel driver as well as an image acquisition device for automated inspection. Testing the various analog video interfaces requires a digitizer or waveform analyzer with >100 MHz clock speeds and more than 12 bits of resolution because most component video is eight to 10 bits. Testing the digital video interfaces requires a high-speed digital analyzer with up to 150 MHz clock speeds to capture 1080p/60 Hz, Full HD video signals. A high-resolution (more than 18 bits) audio analyzer is also required to test any analog audio interface as well as the microphone and amplifier properties.
It is clear that the complexity of a mobile device video test system requires a platform that is powerful, flexible, and scalable for product changes.
Choosing a Test Platform
You must consider several factors when selecting a test platform for mobile devices such as investment cost, development cost, future upgrade costs, throughput, and footprints. Purchasing several boxed instruments for video generation, analog video analysis, digital video analysis, and audio analysis is not a cost-effective approach for testing mobile devices because each instrument costs $20,000 to $40,000 USD and has fixed functionality that could easily be obsolete within one to two years. Another major challenge is that automating boxed instruments requires heavy software development resources. Considering the risks associated with a boxed instrument test platform, it simply is not a feasible solution.
Because of these limitations, many manufacturers such as Sony, Samsung, and Panasonic have moved to a more flexible test platform, PCI eXtensions for Instrumentation (PXI). Within video test applications, throughput is a key challenge due to large amounts of data in a video frame. With higher bandwidth pushing 4 Gbits/s and lower latency at submicrosecond levels, PXI technology provides a faster test platform than traditional boxed instruments.
The PXI system contains three components: the chassis, controller, and modular instruments. The chassis offers a high-throughput PCI bus as well as timing and synchronization buses. The controller, which can be a remote controller from a standard desktop or laptop PC, or an embedded controller within the chassis, runs standard OSs such as Windows XP and common applications such as Microsoft Excel. The third part of a PXI system is the modular instrumentation. There are more than 1,000 modular instruments available from more than 70 vendors that range in functionality from GPIB control to digital multimeters (DMMs) and switches to audio/video analyzers to RF generators and analyzers.
By selecting the modular instruments required for a given application, you can build a complete test solution within a single, low-footprint system that is optimized for automated test.
Another important factor in choosing a test system is selecting the best test framework. Developing code modules to test a variety of audio, video, and LCD components of a mobile device is a difficult task, but maintaining a test framework that scales as new versions of a cell phone come to production or new revisions of a camcorder are released is an even more challenging task. You need a test framework that is flexible enough to scale with your production needs and modular enough to adapt to new revisions, product lines, and technologies. With NI TestStand test management software, you can develop, manage, and execute your test sequences and code modules.
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Figure 2. The PXI platform is ideal for automated test applications that require several instruments, high throughput, and flexibility for future updates. Combining PXI-based instruments with NI TestStand test management software creates a powerful and flexible test architecture. |
NI VideoMASTER and NI AudioMASTER for Mobile Device Testing
NI Video Measurement Suite and AudioMASTER compose a suite of products for analog and digital audio and video testing. They combine modular instruments with a configuration-based development environment that helps you quickly perform hundreds of audio and video measurements to test cell phones, camcorders, and digital cameras. NI Video Measurement Suite and AudioMASTER software offer configurable test steps in NI TestStand that you can easily interchange when new products are released or a new product revision needs new test requirements. Using the PXI platform and high-performance digitizers, high-speed digital I/O modules, and custom video processing modules, NI Video Measurement Suite helps you take hundreds of video measurements, compare them to internal or industry standards, and generate a pass/fail report for the system in just a few seconds. This helps you achieve throughput levels that traditional boxed instruments simply cannot provide.
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Figure 3. With NI Video Measurement Suite and AudioMASTER, you can test analog and digital video as well as analog and digital audio, all within a single, high-performance, automated solution based on the PXI platform. |
By taking common audio measurements such as THD+N, SNR, SINAD, and single-tone amplitude and frequency measurements, you can identify most audio processing errors that result in a poor customer experience. If an application requires more extensive audio measurements, AudioMASTER provides a complete set of tools for frequency sweep, amplitude sweep, Bluetooth, single-tone and multitone, and custom audio processing test. By combining these capabilities with a built-in calibration manager for difficult testing environments such as manufacturing facilities and custom limits editors for monitoring passes and fails, you can develop even the most complex audio testing application.
Using NI Video Measurement Suite, you can test for video defects that cause motion blur, compression distortion, color saturation, or inaccurate resolution changes. By generating known, high-quality analog or digital video into the LCD display of a mobile device, you can watch for any of these errors in the display. By monitoring video outputs (composite, S-video, component, mini-HDMI), you can ensure the camcorder meets consumer expectations for video quality. You can identify and eliminate video defects by performing measurements on the timing signals, blanking intervals, color levels, noise, and frequency response of analog and digital video signals.
A Complete Automated Test Solution
Video and audio testing is only a subset of the tests performed throughout production. Wireless protocols, power management, memory, and other components must be tested often to ensure customers are receiving the highest-quality product. You can customize any application built on the PXI platform by adding modular instruments for RF technologies, power supplies, source measure units (SMUs), switches, or other instrumentation. By architecting a mobile device test system correctly, you can more efficiently scale as production needs increase or new products and design changes force quick modifications in production test.
Additional Resources
View Preconfigured Cell Phone and Digital Camera Test Solutions
Learn more about the NI Video Measurement Suite
Learn about AudioMASTER
View a Case Study for Mobile Device Testing with PXI
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