PBS Makes Progress onFile-Based Delivery

Non-real-time program distribution may begin this year
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Pbs' multi-year effort to create a new transmission system that delivers programming to public TV stations as compressed digital files may finally be coming to fruition, after delays due to lapses in federal funding, management changes and technology hurdles. PBS has already installed "catch servers" for its Next Generation Interconnection System-Non-Real-Time Program File Delivery Project (NGIS-NRT) at 15 stations for "alpha" testing, and if beta testing is successful this fall, it could begin a phased rollout to some 180 licensees by year-end.

The NRT system is the second phase of NGIS, a federally funded, 10-year, $120 million initiative to overhaul the transmission infrastructure that PBS, along with American Public Television (APT) and the National Educational Telecommunications Association (NETA), uses to deliver about 200 hours of programming each week to public TV stations. The first phase of NGIS, which replaced satellite receivers at stations and shifted linear feeds to a new SES satellite (AMC-21), was completed through 2007 and 2008.

Since only about 25% of PBS programming consists of live feeds that are "passed through" and broadcast locally at the same time, PBS is seeking a more efficient way to deliver content that will be recorded, stored and played at a later date. It initially issued an RFP (request for proposal) in 2005 for an Internet Protocol (IP)-based system that would transmit programs to "catch servers" at stations, instead of sending them as real-time program feeds via satellite that need to be physically recorded by a video server or tape deck. The catch servers would then communicate with stations' traffic systems and playout servers to push content to air.

When Congress held back some $35 million in funding in 2006, the NRT project was put on hold, and a new RFP was issued in May 2007. The departure of top PBS engineer Ed Caleca in fall 2006 (subsequently replaced by current CTO John McCoskey) and the lengthy process of ratifying AS-03, PBS' implementation of the Material Exchange Format (MXF) networking specification that would be used in the NRT system, also helped to delay the project, say executives from PBS member stations.

But PBS has now identified key vendors for the catch servers, which will transfer the program files to playout servers and perform any transcoding necessary to make them work with different vendors' servers. There is also a software module, called the Station Services Platform (SSP), which links directly to the station's traffic system (in most PBS stations, that is Myers ProTrack) to automate the process.

Like existing file-based commercial and syndicated program delivery systems from DG FastChannel and others, the catch servers will use a broadband connection to communicate back to PBS to confirm receipt of the files and notify it of any missing bits that need to be resent. The broadband connection will also allow PBS to remotely purge content after its rights window has elapsed.

10 days' worth of storage

The catch server will have 12 terabytes of storage, enough for 10 days of content, according to Jerry Butler, senior director of the Interconnection Replacement Office for PBS. The files will be encoded using MPEG-2 at high-quality mezzanine compression rates-33 megabits per second (Mbps) for HD video and associated audio, and 13 Mbps for standard-def video and audio.

The devices are based on an HP DL380 G6 computer platform, with International Datacasting Corp. providing the satellite receiver and file transfer system. Encoding and transcoding for NRT is being supplied by RadiantGrid Technologies, which PBS already uses at its Virginia headquarters to prepare content for new-media platforms. PBS has tapped Communications Engineering Inc. (CEI) to help stations install the rack-mounted catch servers, and has contracted with Hughes Network Systems to install dedicated broadband links to the devices at each station. While these DSL-quality links are known as Terrestrial Data Paths (TDPs), they may in fact be VSAT links at some rural outlets.

Engineers at PBS stations say there is still some significant software development that needs to be done this summer for the NRT project to enter beta testing this fall. But Butler is optimistic that the project will stay on schedule and that PBS can begin the rollout late this year or in early 2011. As he puts it: "I would love to be finished with this project by the end of next year."

Since PBS' goal is to be able to deliver some 40 hours of content daily to the catch servers, providing faster-than-real-time transcoding between the catch and playout servers is key to making the investment in NRT pay off. RadiantGrid will be preparing the files using the aforementioned AS-03 spec, which server manufacturer Omneon has already agreed to support. But it may need to transcode the files to make them compatible with other servers. Individual PBS stations also handle audio differently, and while PBS currently distributes PCM audio, it wants to move to AC-3, which would also require transcoding at the catch server at many stations.

More important, PBS eventually wants to take advantage of MPEG-4 compression to significantly cut down on its satellite bandwidth, and the catch servers would need to transcode MPEG-4 files to MPEG-2 to work with legacy servers.

Kirk Marple, president and chief software architect for RadiantGrid, says his company's company's CPU (central processing unit)-based grid transcoding technology can deliver faster-than-real transcodes while retaining and managing important metadata, such as closed-captioning information. He says his company is also considering a partnership with a GPU (graphical processing unit)-based transcoding vendor, such as Elemental Technologies, to improve the overall transcoding performance of the NRT system.

"We've always looked at transcoding as part of the long-term plan," says Butler. "It puts us in the right position to implement MPEG-4 down the road, and it also covers us for variables in the servers that are out there. Most of the big names have signed on [to support] AS-03, but some smaller ones may not make the move."

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