DENVER
Although perhaps only the most discerning NFL viewer at home was aware of it, brief portions of the regionally televised Broncos-Browns game earlier this season offered a rarity—and perhaps a glimpse of the future—in these early stages of the digital age: uncompressed HD-SDI video backhauled via fiber optics for end-to-end delivery from Denver to CBS studios in New York.
The brief informal sampling of uncompressed imaging captured at Invesco Field for CBS Sports will be among several opportunities that various broadcast networks will be afforded at various NFL games in Denver this season to backhaul uncompressed HD content all the way back to their CRs back home (which, in the case of Denver to New York, is about halfway across the continental United States).
A MORE DIRECT PATH
The uncompressed content is being delivered by Level 3 Communications, leveraging its Denver-based IP network and Vyvx fiber-optic scheme first used more than a year ago when the firm provided an uncompressed 1.5 Gbps feed from Denver for coverage of the 2008 Democratic National Convention. (In typical scenarios, a broadcaster's live video is fed to a production truck adjacent to the stadium and compressed before being sent on to studios back home—a mode that Level 3 will continue to keep during the current shakeout period.)
Level 3 ops center Bob Mincieli, director of broadcast operations at CBS Sports, likes what he sees. "It takes our encoders out of the equation. It's more of a direct path. There's less levels of things that might fail or cause issues. And the video is pretty good-looking, too. From my vantage point looking at a 10-inch monitor [in the truck], the uncompressed looked a bit crisper. It's certainly as good as the 270 [Mbps], and arguably a little bit better."
Mincieli said the brief Denver sampling in the Cleveland game worked fine, "Although it was a little bit unheralded because we sort of began that day considering the [uncompressed] video as a test line," he said. "And then as that day progressed, and we were pleased with how it looked because we conducted some end-to-end with some stations, we decided to use the video for a time in the final quarter. I wasn't privy to any specific station feedback from it, if there was any, but everyone was pleased within with the CBS sports division. We continue to talk about it and will likely see more [uncompressed usage] as the NFL season progresses."
Driving Level 3's uncompressed video relies on HBRAV-IP—the high bit-rate audio visual-over-IP system being molded into a standard for the encapsulation of signals up to 3 Gbps, (see sidebar). Level 3, based in Broomfield, Colo., said the adoption of a standards-based solution will allow tech vendors to focus on various management and control systems which it believes are critical to building large-scale networks and driving costs down.
Derek Anderson, senior product director for Level 3's Content Markets Group, said there are three distinct advantages to using uncompressed HD-SDI for backhaul transporting—quality, latency, and less complexity.
"Quality, of course, because the signal is never compressed throughout the transmission path and is never degraded," he said. "This also allows archive copies to be a perfect representation of the camera signals, and it allows for a higher quality signal as the input to the distribution encoders."
Also, Anderson said removing compression hardware reduces the latency of backhaul transmission, which is one of the biggest delays in the transmission path when using compression. That, in turn, "eliminates additional points of failure and complexity within the signal path. Providing a service which allows the broadcaster to hand off the uncompressed HD-SDI signal means there are now two things it doesn't have to worry about—the encode at the [remote site], and the decode back in master control."
THE 'COMPRESSION PARADOX'
For Level 3 right now, the biggest challenge is local access. "Where you have end-to-end fiber connectivity that you own and control—as we have at Invesco Field in Denver back to the broadcast studios—we've demonstrated it can be done. And although the flows are bigger and there's different equipment, the underlying service we're providing is basically the same as we've been doing for years," Anderson said. "The current challenge is having HD-SDI video-loop access across a national footprint. As we see HD-SDI availability increase—just as we saw 270 SD-SDI availability grow during the transition away from analog local-loop access—we can expect adoption of uncompressed HD services to grow."
Historically, and for mostly economic reasons, the cost of buying and running encoders/decoders for SD video had always been less than the cost of consuming more network capacity to carry the same signals in their native uncompressed forms. But now Anderson sees a "crossover point" where Level 3 has become "indifferent" between encoding SD video and carrying it uncompressed across its Vyvx network. "We've labeled this the 'Compression Paradox.' In other words, why compress [SD] video if there are no underlying economic or service reasons to [continue to] do so?" Anderson said. "As the economics of running fiber networks continue to evolve, we believe at some point a similar crossover point will be inevitable for moving HD video."
Yet even if HD content is fed uncompressed all the way back to networks' main CRs, what about that often-cited "last mile" to the home where tens of millions of pay-TV viewers likely would still be receiving cable-compressed HD? Lynn Claudy, senior vice president for Science & Technology at NAB believes from an industry point of view, "The long tradition of 'broadcast quality' implies that image quality will be maximized to the highest extent possible for the services being supplied—based on the capacity limits of the transmission medium."
While Claudy acknowledges the "last mile" transmission to the home is typically compressed due to the limits of 6 MHz of bandwidth for over-the-air transmissions, he believes increased upstream bandwidth may allow for much higher quality to be maintained all the way from production to just prior to OTA transmission. "The increased availability of uncompressed HD during the acquisition, distribution, backhauling and other portions of the broadcast chain is an option that will no doubt please the quality-conscious professional broadcast community," Claudy said.
Adds Level 3's Anderson, "Providing an uncompressed signal—even if it's only for the initial backhaul transmission in the end-to-end chain—still provides a better quality end-signal into the home."
What is HBRAV-IP?
Level 3's uncompressed HD feeds use High Bit Rate Audio Video over Internet Protocol. Initial work on HBRAV-IP was conducted in the Video Services Forum as a follow-up to previous efforts the forum had assumed from the ProMPEG Forum, which involved the transport of MPEG2TS-over-IP.
John Dale, vice president at Media Links, Inc., in Milford, Conn., and co-chair of the HBRAV-IP Group, also serves as technical editor for HBRAV-related documents now passing through a SMPTE 32NF Video-over-IP ad hoc group for eventual standardization. He said HBRAV-IP has its roots in ProMPEG Forum COP4 and IETF 3497, and was improved by manufacturers, service providers and end users who participated in the HBRAV group within the forum.
Dale's group focused on uncompressed native HD/SD content, as well as light compression using JPEG2000 over IP. (The priority of previous work had been on lower bit-rate, more highly compressed signals.) "The vision of the team was that legacy dark fiber or SONET/SDH video implementations will give way to Ethernet/IP implementations," Dale said. "The thinking is this new approach will ultimately provide more ubiquitous, higher-quality, lower-cost services." (HBRAV applications, despite using IP technology, are intended to be used on robust QoS private networks.)
Dale uses the example of a long distance video signal transport path: A signal must traverse a dark-fiber local loop on both the send- and receive-side with compression codecs and the SONET network in the middle. Crosspoint video routing switchers at each network intersection must be configured. However, with an IP network, video is adapted to Ethernet/IP only once, on the access side, and then traverses the network from end to end as IP packets—and is only transitioned back to video at the receive site. This latter scenario is simpler and provides fewer potential stumbling blocks, Dale said.
Since the HBRAV-IP initiative recently moved on to SMPTE for standardization, a work statement has been approved by the SMPTE 32NF Video-over-IP Ad Hoc Group.
