Video Gateways And Servers Matter, Too
When it comes to delivering video content via IP over farflung networks, video compression or encoding solutions represent just one part of the equation. Video gateways complement encoders by preserving the quality of compressed video during end-to-end transmissions. All the efficiencies gained during the compression process are of little value if the IP video or content arrives at its destination in anything less than the highest possible broadcast quality.
According to Dan Album, spokesman for Path 1 Network Technologies Inc., gateways such as Path 1's Vx8000 video gateway are used in numerous satellite-related deployments, primarily by broadcasters who move video over terrestrial IP networks (such as among their various studios) and then send post-production video content to their satellite uplink facilities for worldwide distribution. CBS and Fox Broadcasting, for example, used Path 1's equipment as both the primary and backup technologies for their respective 2004 and 2005 Super Bowl broadcasts in HD, according to Album. "In many ways, long-haul video transport is the most critical link in the video distribution chain. Video sent over IP networks is subject to many errors -- delays in the packet stream, lost packets, packets arriving out of sequence, image jitter, etc. Path 1's gateways corrects these transport errors and ensures that whether you are sending video across the street or across the world, it will maintain broadcast quality when it arrives at the uplink facility," he says.
"Compression removes information and bits, so any problems or hiccups during transmission are amplified accordingly. Macroblocking, dropped frames, etc. are more likely to be enhanced (in a negative way) if the transport is not perfect. This is especially problematic in cases where video needs to move over long distances, Album adds. "Gateways are the best way to maximize the investment in these expensive encoders -- particularly the HD-AVC encoders."
SD and HDTV delivery aside, Alcatel Alenia Space announced in early 2005 that it had installed DVB-RCS gateways provided by Quebec-based Xiplink Networking, a subsidiary of Xiphos Technologies Inc., in the Middle East and will soon install them in Northern Africa Among other things, the Xiplink Hub Optimized Gateway compresses HyperText Transport Protocol (HTTP) data more efficiently and automatically, says Alcatel Alenia Space spokesman Laurent Zimmerman. "Satellite user customers get a better web browsing experience," he says. "A Performance Enhancing Proxy (PEP) at the hub isolates the service from any weak behavior of the Internet or any servers behind or, more precisely, from servers that do not support TCP-sat options such as extended window or selective acknowledgements. In brief, it helps the satellite access provider to commit on service delivery relatively independently of the internet network or service providers."
Xiplink focuses on a hub-only solution aimed at optimizing interactions at the Transmission Control Protocol (TCP) and HTTP layers in DVB-RCS environments, and this enables users to shape network traffic to match network bandwidth without displacing Quality of Service parameters. The Xiplink Hub Optimized Gateway offers a forward channel of 45 Mbps and a return channel of up to 20 Mbps. Optional client browser tuning can further enhance performance. "The Xiplink Hub Optimized Gateway is a solution for improving the efficiency and performance of broadband IP access systems. Installed at the hub, the system optimizes the TCP flow while allowing the independent enforcement of QoS and service level agreements," says Charlie Younghusband, Xiplink's product manager. "The HTTP compression alone provides a reduction of approximately 15 percent in bandwidth utilization, permitting more users on less bandwidth."
While Xiplink is not unique in this respect, Alcatel selected Xiplink because of a requirement by some customers that mandated PEP transparency to IP addressing. "The hub only solution is not more difficult to implement than PEP with clients on remote sites. In any case, you have to integrate and tune the PEP product to the dynamic behavior of the hub and satellite terminal in terms of available memory and resource allocation," says Zimmerman.
"Satellite streaming is basically used in a multicast streaming environment. Multicasting is more difficult to do and more expensive to set-up. Multicasting is mainly geared towards Intranets. Among the benefits, it allows multiple viewers of one video stream which saves cost on bandwidth and a video stream can bypass the Internet and be placed directly in an Intranet," says Derrick Freeman, video streaming and compression specialist at GeniusDV. "However, most networks are not multicast-enabled and the Internet is geared for unicasting, rather than multicasting. And there is need for IP/DVB PC cards -- a card to view any satellite streaming is a hindrance for larger audiences especially -- and for satellite receivers as well."
As Zimmerman mentioned, servers can present problems. Envivio has developed a server designed specifically to support the streaming of AVC in IPTV, enterprise and broadcast deployments via its ability to handle MPEG-4 systems content, which is known as Binary Format for Scenes (BIFS).
"The BIFS capabilities within MPEG-4 allow the delivery of complex interactive multimedia scenarios. The key advantage of BIFS is that individual objects within a multimedia scene are encoded and transmitted separately," says Trow. "A server that can process BIFS has two key benefits: increased workflow since complex scenes comprising of multiple objects can keep the objects as separate entities right up to the STB, and the inclusion of mixed graphic and pictures in a scene. Among other things, this dedicated server approach also allows middleware to be based around standard network infrastructure, greatly reducing the cost of system implementation," adds Trow.
"Along with the enhancing video compression technology, strong management capabilities of the available network bandwidth capacity, as well as the flexibility of the satellite network topology for video contribution and distribution is key. This will enable service providers to offer attractive services with competitive commercial conditions to their customers," says Neu.
Conclusion: Juggling Costs And Bandwidth Resources
While delivering highly compressed digital video as IP may be the ultimate destination for the global television sector, the timetable is open to question. Issues such as overall network security and reliability and where exactly television is heading in terms of its future menu need to be resolved before the conventional broadcast world gives way to a fully enabled interactive, pulled content or on-demand model.
"The technological and business shifts required for that are too significant to be able to do it in the short or medium term. Eventually though, it would appear to be the best option for the consumer and we have now developed the technology to enable it," says Aditya Kishore, director, media & entertainment strategies at Boston-based Yankee Group. "From here on it is more a question of technology evolution to support the scale and bandwidth required, and the development of new business models to support it economically -- new advertising formats, audience measurement solutions, metrics, etc.
"The problem is that there is a very significant investment that has already been made in existing equipment. So it is a question of managing the transition in a cost-effective manner. On the one hand, for cable, IPTV, and DBS service providers, there is a need to manage limited bandwidth resources with the growth of HD, VOD and increasing broadband connection speeds. On the other hand is the cost of replacing equipment," adds Kishore.
Long term goals aside, a migration to advanced compression schemes like MPEG-4 AVC appeals to everyone. However, like anything else, is a matter of resources and budgets. Coming up with a cost-effective transition strategy and then implementing it in a measured manner is what counts.
"All of the bits and pieces are there. We see the market looking for more turnkey and outsourced solutions. Customers are looking to work with service providers who will provide a comprehensive solution, including compression and satellite equipment as well as space segment. The video owners simply want to hand off their video signal and know that it will arrive at the other end," says Semperbon.
Peter Brown is Via Satellites's Senior Multimedia & Homeland Security Editor.
Email
Comments
Print
Reuse
