Whatever the combination of digital video technologies, quality of experience (QoE) seems to be the word of the day. With competition and expectations both on the rise, ensuring that consumer QoE is high has become increasingly more important, even as it has become more difficult to achieve.
In fact, the Comcast Media Center (CMC) has identified eight touch points where video quality should be measured, including:

  • content source
  • master control facility
  • MPEG encoders and multiplexors
  • point of entry into CMC facilities where MPEG is encapsulated onto IP
  • interface with the IP delivery system
  • QAM devices
  • set-top box
  • consumer video display

According to CMC VP Quality Assurance Dave Higgins, there are a lot of testing tools available today. Some measure delivery of content, whether the pipe is working, what types of impairments could be impacting video. The CMC also has a video processing grading system to determine HD delivery performance.
But he’d like it to do more.
“What that system doesn’t do is measure impacts downstream,” Higgins said. “There is not a device out there per se that would allow us to plug video into it and give you a numerical rating or some kind of rating to tell you how good the video looks.”
The CMC is looking for a device that would give it a real-time assessment of the impairments, by way of what Higgins termed a video mean opinion score (MOS).
Vendors are working towards this Holy Grail.
“I see an evolution where probes look at content, look at the TV set like a subscriber,” Rob Flask, product line manager, JDSU communications T&M business segment, said. “Right now (they) are looking at things like frozen black screen, low and high audio, for gross errors.”
Flask said that one goal is for the technology to evolve to the point where the testing equipment says, ‘the picture doesn’t look good.’
Still looking toward the future, Eric Conley, CEO, Mixed Signals, said MSOs also are asking for real-time 24/7 monitoring further out in their networks. “Pretty soon, we will be monitoring out to the customer premise and it will all be tied together in a unified view of the health of the entire network.”

T&M tools, today

Testing tools are using MPEG transport stream standards (ETSI 101 290) and measurements to check metrics on pixelization, tiling, frozen video and missing audio tracks, beginning at the content source.
“If there is a problem, which does happen from time to time whether it be a faulty camera or compression equipment, (the MSO) would want to know before it gets to millions of customers,” Frances Edgington, vice president HEYS Professional Services, said. (For more from Edgington, click here.)
An MPEG transport stream analyzer can be used at several points throughout the transmission network, including at the headend and wherever there is a switch or edge router.
“You want to test (content) before it is turned back into an ASI stream and sent to the edge QAM,” Trilithic Product Manager Thomas Powell said. “You want to verify content before it is sent to customers to know it is good. (An MPEG transport stream) product will help them at least at hubs, to identify whether or not the content is a problem or if it is a true RF issue,” Powell said.
Whereas older tools dealt with things like packet loss and jitter, those may not be the biggest problems in the network. “It is the manipulation of video at the MPEG layer at the edge,” Ron Shanks, director of marketing, JDSU communications T&M business segment, said.

Over the edge

Operators today must aggregate and transcode video close to where they distribute it via QAM streams into neighborhoods or nodes. All of which adds up to a challenge.
“Different formats, different compression techniques, different issues…make testing at the edge more difficult to monitor and troubleshoot,” Flask said.
Problems stem from program clock reference (PCR) timing issues and multiplexing. “It is a challenge for us, how to do those types of measurements on a broad scale and measure all programs at all times for these parameters,” JDSU’s Shanks said, adding that flexibility matters.
Shanks said JDSU’s MVP-200 MPEG Video Probe is a “hybrid network analyzer in probe form” that can monitor 24/7 or troubleshoot.
Likewise, Trilithic’s Faultline MPEG Analysis Suite, is software based.
“If (it) is on a server class machine and you need to go to a hub site, you can install it on a laptop and use the security dongle,” Powell said. The analyzer can monitor 1024 streams per second and costs less than $6000 per software license.


Testing and monitoring have also advanced in the realm of SDV and VOD, which bring their own challenges.
With the former, each individual makes a request for a channel. “ESPN doesn’t stay on the same RF frequency. It is dynamic,” Calvin Harrison, IneoQuest VP business development, said, noting that VOD offers similar circumstances.
“MSOs haven’t had a good way of tracking when the request was made, did it play,” Harrison said. His company’s IQ Dialogue SDV server probes monitor transactions between set-top box, SDV server, edge resource manager and edge QAM.
“We sit in the middle of that watching, storing, and capturing all communications,” he said.

Audio angst

On the audio side, the U.S. House of Representatives passed the Commercial Advertisement Loudness Mitigation (CALM) Act in the fall and referred it to the Senate Committee on Commerce, Science and Transportation in December.
The legislation calls for service providers to be fined for loud audio, a common problem as volume levels can vary depending on the channel, program and particularly commercial.
“Companies are trying to get ahead of this. If they know they have to find a solution, they figure they better do it on their own terms,” Mixed Signals’ Conley said.
The idea is to measure and monitor volume against the dial norm, and send an alarm if something crosses the threshold for more than a certain period of time, Conley said.
Mixed Signals has a software upgrade that will support the ITU-R BS.1770 audio specification. “The end fix is to re-encode,”Conley said.

–Monta Hernon

The Daily


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