The traditional testing of new audio/video (A/V) standards or device involves creating a customized test system with various box instruments to suit the specific test requirements of the DUT. This method is tedious, time-consuming and a very expensive proposition.
Typically, such a customized test system (Figure 1, below ) is very rigid and a whole new test system has to be recreated again whenever another standard or device comes about.
|Figure 1: Here's an illustration of a hybrid test architecture comprising instruments across a variety of communication buses, which is controlled by the main controller (e.g. a PC or PXI System|
Many manufacturers are now beginning to realize the detrimental consequences of the traditional approach and the limitations of these test systems when challenged by the converging complexity inherent in modern devices. Thus, it is imminent that manufacturers will adopt the new method for A/V test known as the software-defined approach.
A/V devices are now cramped full with modern technologies and multiple functional abilities to support various industry-defined standards to meet the customers' demanding needs.
To stay ahead of competition, manufacturers have to innovate to cut down their development and test time, shorten time-to-market, and come up with a flexible test system capable of testing a broad spectrum of products that will pare down test and development costs as well.
A software-defined approach to A/V testing (Figure 2, below ) is the new and innovative approach, providing A/V manufacturers the edge needed to push their new products to market faster. This concept to A/V testing will be the definitive approach for the future.
|Figure 2: Shown is the software-defined approach towards test adopting a hybrid test architecture. The main controller will control all the test instruments, and handle the testing processes and programs required for each DUT.|
In short, there is only a set of physical test instruments connected to a main controller where the software program will determine the test required depending on the DUT. Let's look in more detail on how this can be achieved.
Remember the main objective for a software-defined approach in A/V testing is to reduce expenses and time during test and development stages.
Note that there is no “one size fits all” methodology. To create a cost-effective and flexible test system, the utopian approach is to build a hybrid system that combines test instruments from various platforms such as PXI, GPIB, VXI and LXI that allows engineers to choose the best approach for each test application in software.
With a variety of communication buses available, each with its own strengths, hybrid systems are a good option for test systems since they provide greater system flexibility. When you choose only one bus or platform for a system, you are limited to the instrumentation available for that bus.
This limitation prevents you from adopting another instrument that might be better suited for your system needs. When selecting instruments, you want to choose instruments based on specifications like performance, accuracy and measurement availability.
By removing the restriction of using only one bus for the system, you open up the possibilities for instrumentation. Some buses and platforms provide highly specialized instrumentation, while others provide instruments at a better price and performance combination.
Test instrument makers acknowledge that no single instrument architecture is superior in every aspect. A hybrid test system allows A/V test developers to shop around the market for a wider range of test instrumentation.
From traditional test-specific box-instruments using GPIB or LAN/LXI communication buses to modular instruments using the high-bandwidth PXI/PXI Express or VXI bus, developers can merge the best of each heterogeneous buses and platforms to suit their testing requirements.
Such systems are long-term cost-effective solutions to achieve test system longevity by selecting appropriate test instruments for a wider range of DUT.
The design flexibility of a hybrid architecture lets test developers strike a balance between the optimized functionality of dedicated instruments and the ability of virtual instruments to quickly address new test requirements.
For instance, high power or extreme precision measurement or generation may require a GPIB or LXI instrument, while high-speed digitization may need PXI or PXI Express.
On top of this, upgrading and expanding the capabilities of a hybrid test system is made simple with the support of multiple communication buses—from daisy-chaining GPIB box-instruments to additional PXI/ PXI Express modular instruments into the PXI chassis.
In the heart of the hybrid test system, there will be a main controller, which controls all the test instruments via a central operating system. This holds key to be the centerfold of a software-de- fined approach towards test.
This concept allows test developers to control all the connecting test instruments, synchronize the test process, optimize the test program and modify the existing test codes for testing of another product using the same instruments. In short, within the same controller, there can be various test programs and parameters to perform tests for various DUTs.
Only the testing parameters of each product will differ from the next, but the testing methodology of A/V standards or functions remains the same. This statement holds especially true in the A/V testing context where a number of test requirements are similar among various products. Suffice to say, having the ability to re-use existing software test programs is a very favorable advantage to test developers.
With the hybrid test system approach, test developers are able to use their preferred software development environment where they are proficient in to reduce test development time.
Compatibility issues between test instruments and operating systems are the major concerns for any test developer, especially when mixing different test instruments old and new. Instrument makers used to design custom software that can only work with their own instruments.
Fortunately for us, these practices are now things of the past. Today, test instrument providers are making their instruments “plug-and-play-friendly” by creating drivers following industrial software standards, e.g. Interchangeable Virtual Instrument (IVI) drivers and Virtual Instrumentation System Architecture (VISA), helping to simplify software development for test developers. Data analysis is increasingly playing an important role in determining whether products PASS or FAIL in modern test systems.
The traditional approach towards test had always made data analysis for test systems an expensive and drudging process. Additional test instruments and customized hardware were required to be built on the existing test system to provide data analysis capabilities.
Today, with the improvements of computing technologies in multicore CPUs and high-bandwidth memory, we are seeing unprecedented levels of power to process data faster than before.
And by using the software-defined approach on a hybrid test set-up, measurements can be recorded and controlled directly from the various test instruments via the software through the main controller. It also allows the data analysis for test systems to be performed directly during testing.
The beneficial results can be seen immediately—the testing software applications are optimized and the handling processes of test data are streamlined. It is truly a vast difference from the conventional test instrumentation that will create a bottleneck in data analysis and slow test systems down.
Compared with the conventional test architecture, the hybrid test architecture allows for new test instruments to be added or removed from existing hybrid test systems much easier than before. With more and more test instrument makers adopting the VISA and creating IVI drivers for their new products, it also creates the modularity that give test developers the flexibility to enhance their test system capabilities in the software realm. The hybrid test system can therefore stretch its capabilities based on the specific requirements of each test set-up.
Preserving investments In the ever changing landscape of A/V technologies and standards, it is a constant challenge for manufacturers to come up with new products that keep up with or exceed customers' expectations.
For example, a manufacturer decides to produce a device based on a certain technology, but the market demand for products with this technology diminishes; the manufacturer that adopted the traditional test system approach for this product will suffer a heavy investment loss.
With the software- defined approach using the hybrid test system, manufacturers will be able to preserve their investment outlays as their hybrid test systems can be easily redeployed with minimal hardware changes and software development to suit the new project requirements.
Imagine this scenario: One manufacturer may have a team of engineers working to develop product tests such as digital video quality, digital audio, analog video and analog audio testing for a new high-definition (HD) TV STB. By adopting the software-defined approach, the same hybrid test system hardware set-up can be ported easily to test another product with minor modifications. Another team of test developers could be tasked in creating tests for a high-power audio amplifier.
By omitting the digital and analog video tests programs and modifying the digital and analog audio test programs created for the HDTV STB slightly, the test developers will be able to port the hybrid test system over to test the high-power audio amplifier. Hence, the test development cycle time and test systems costs will be dramatically reduced.
The competitive advantages of software-defined methodology do not end here. Manufacturers can also use the same approach on hybrid test architecture to determine the suitability of constantly evolving standards to be adopted in their upcoming products by doing a rapid prototyping and testing evaluation.
In conclusion, A/V developers will reap benefits if they can adopt the software-defined approach on hybrid test architecture during the design and prototyping phases of the product development stage. Having a standardized platform from development test to production test will greatly diminish the test and development time and therefore lead to cost savings. As the saying goes, time is money.
Ken Ng is a Marketing Engineer at National Instruments Corp.