Field Report: Video Clarity’s RTM—Reference-Based QC Testing in Real Time

Broadcasters have always checked their networks for performance. There now is a process that enables the testing to include a true QC measurement of the content as it passes through the entire broadcast chain.

In order to retain — and gain — viewers, subscribers, and advertisers, program originators and distributors must be able to deliver a consistently high-quality product. And the only way to know they’re succeeding is to measure their audiovisual content and determine if it meets standards — whether those standards are self-imposed, set by the customer or compliance regulators, or some combination thereof.

That’s why conscientious broadcasters and others make a point of monitoring and testing the quality of their video signals in real time. The testing process has traditionally existed to check network performance and delivered programming after it has gone to air — the basic definition of QC. Now this process is evolving to include quality measurement as well. That is, measuring the true quality of any given content throughout the entire processing chain.

Video Clarity’s Real Time Monitor (RTM) allows content distributors to make continuous quality measurements during actual broadcasts on all types of video delivery systems, including broadcast, satellite, cable TV, and Internet streaming. This technology provides a way to detect and measure many different kinds of errors that can affect video signals. The resulting measurements are compiled into a score using a mathematical formula based on accepted studies of human visual perception. The score indicates how much video signal quality degradation a typical viewer would notice. From there operators can make adjustments as needed.

This example shows long-duration monitoring. With a return link for data, Video Clarity's RTM measures multiple QC parameters including; A/V quality, lip-sync (offset), audio loudness and VANC data lines.

This example shows long-duration monitoring. With a return link for data, Video Clarity's RTM measures multiple QC parameters including; A/V quality, lip-sync (offset), audio loudness and VANC data lines.

Reference-Based Testing: The Key to Accuracy

RTM relies on reference-based video quality testing — specifically full-reference testing — whereby the quality of the output is measured against the source content. With this method, the equipment performing the test receives two copies of the content: a source (or reference) version, and a version that has been processed through some type of network or equipment. Full-reference testing is the most accurate way to arrive at an idea of human-perceived video quality because there is a frame-by-frame comparison between the original and the processed content, with standards-based, repeatable calculations being made between the two. This powerful technique allows measurements to be made in-service, so that normal video delivery can continue uninterrupted while tests are underway.

The Big Benefit: Objective Numbers to Back Up the Eyeball Test

A full-reference solution eliminates the need to rely on visual comparison alone when making quality decisions. While the QC and measurement process will always require experienced engineers to “eyeball” the content, full-reference testing gives them an objective, highly accurate, numbers-based method and scoring system for quality that correlates to the subjective score they would assign during visual evaluation. Having a highly accurate quality-measurement method to match their perceptions is critical, especially given today’s complex and dynamic content delivery environment. This reliable scoring system can be used throughout the delivery chain and applied consistently to all types of content no matter what the delivery method.

Broadcast, Cable and/or IPTV Head End Operational Diagram

Broadcast, Cable and/or IPTV Head End Operational Diagram

Reference-Based Testing During Broadcast

As video is being transmitted, operators can deploy reference-based testing at any point or points along the transmission path to compare two video streams. Monitoring throughout a distribution network can give operators a deeper understanding of the effect of errors at each stage along the overall path. RTM notes any differences in the streams and calculates a score. The system provides alerts whenever an error causes visual, audio, and ancillary data glitches; reports if lip-sync problems occur; and saves the exact error frames surrounding the event for immediate or later analysis.

Reference-Based Testing in the Lab

Real-time monitoring and measurement is not just for testing during playout. With the relentless march toward IP delivery and the rapidly expanding range of Internet delivery requirements, methods, and devices, operators have to ensure the quality of the viewing experience well beyond the TV set. Shrewd content distributors are using real-time reference-based testing in their labs to test processing equipment and sample network paths thoroughly for quality of adaptive-bit-rate audio and video streams, with the aim of perfecting their Internet program delivery.

Whether it’s used for broadcast quality-monitoring and error-recording, automatic analysis of IP streams, or product and process testing, real-time, reference-based quality testing with RTM will cut costs, reduce customer churn, and provide a visually appealing product for viewers. As more and more revenue comes from adaptive-bit-rate OTT content, the ability to measure video quality in a highly accurate way is critically important to ensuring that viewers get the best experience, advertisers are satisfied, and regulations are met.

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