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Effective Quality Testing for 4K

What’s the Next Big Thing in the ever-changing world of video formats and resolutions? By now, the answer is clear:  4K resolution and its delivery on Ultra HD (UHD) televisions, digital cinema platforms, and a wide and growing range of streaming video devices. With the emergence of new compression standards such as High-Efficiency Video Compression (HEVC), which offers a potential bit rate reduction of up to 50 percent over H.264, 4K services are looming ever brighter on the horizon.

Therefore, broadcasters and service providers are now gearing up to deliver 4K content to a wide range of services such as real-time TV channels delivered through cable IPTV or satellite, file-based delivery of VOD content, and streaming content over the Internet. Just as with the transition to HD broadcasting, operators have to figure out how to record 4K content, how to edit and package it, and how to display it. But all will be for naught if they overlook one critical element – quality testing.

Video quality testing requirements

In the near future, a critical success factor for broadcasters will be testing and analysis tools that can support any current and emerging formats including 4K. Although there is still a certain amount of SD content in the broadcast chain, the most practical testing tools focus on prevailing HD formats while also including support for SD, with the ability to test content from any compressed or uncompressed video source using today’s SDI-type interfaces.

Testing and analysis should focus on key resolution levels. At the bottom tier are the streaming formats for handheld devices and PCs, and directly above are today’s most active broadcast-level HD formats including 720p or 1080i. The next resolution tier is 1080p 50- or 60-frame rate, a format that’s often required for transmission of a live event over a dedicated network, in-production dailies, or an HD camera feed that needs to be transmitted for production purposes. The final tier, of course, is 4K resolution.

For 4K broadcasting, the most important capability will be the ability to ingest from any source, record it in 4K resolution, and then play it back in every resolution for delivery to every screen. This includes signals from an IP network, an uncompressed video infrastructure feed, or a file from the editing suite. A secondary requirement is the ability to decode any encoded file in the current MPEG or JPEG standards as well as emerging encoding standards such as HEVC. Finally, the system must be able to play back the content in every resolution required for delivery to every screen, from UHDTV and HDTV to mobile device resolutions.

What about audio?

Adam Schadle

In general, operators require three key audio quality measurements. The first is perceptual quality, which simulates a human perception test and creates a measurement that is as close as possible to an actual subjective study done in a standardized environment. An important benchmark for this is Perceptual Evaluation of Audio Quality (PEAQ). 

Next are audio performance measurements that identify performance issues with audio devices or audio in the network chain. These tests enable operators to find audio faults such as silences, glitches, and audio/video offset (lip-sync inaccuracies). The testing system logs the failure and simultaneously records the offending video in a real-time test session.

Finally, testing for audio loudness has become extremely important with the adoption of global loudness standards. This involves applying loudness standards to every individual audio channel and reporting a measurement for a program as a group, as well as true-peak audio measurement.

4K quality correlates to success

As competition heats up in today’s multiscreen media landscape, the winners will be operators that can produce the most reliable, pristine signals and the best possible 4K viewing experience in every format and on every screen. Failure to do so can affect every aspect of a broadcasting operation: viewer satisfaction and loyalty, ad revenue, service level agreements, and compliance. Therefore, the right tools and approaches for analyzing 4K video quality will be essential for success in the coming world of 4K content delivery.

Adam Schadle is Vice President at Video Clarity.