KLCS shifts to DTV

When KLCS-TV, a non-commercial educational television station licensed to the Los Angeles Unified School District (LAUSD), made the shift to DTV in April 2003, the station achieved a great deal more than meeting an FCC mandate. With the support of the Board of Education, the Superintendent of Schools and the station general manager, KLCS took the first step in realizing its goal of providing a broad variety of educational content directly to the desktops of nearly one million students and teachers in the LAUSD.

The digital infrastructure offered more than just the opportunity to go tapeless; it gave the station a chance to leverage some of the inherent advantages of digital transmission for innovative applications — especially in the classroom.

The start of simultaneous broadcasts of a digital signal on channel 41 DT and analog on channel 58 provided a foundation for new services including NVOD, multichannel broadcasts, HD and datacasting.

The first step was to subdivide the digital bandwidth into concurrent subchannels. This multicasting plan allowed the station to deliver content to classrooms by broadcasting video and data over 10 streaming channels.

This strategy for changing the way digital content can be used within the classroom is called daypart bandwidth management. The station broadcasts the main OTA DTV channel from 8 a.m. until 4 p.m. while simultaneously delivering four to 10 high-resolution (WM9 @ 1Mb/s) streaming specialty channels directly to students’ and teachers’ desktops.

At the close of the school day, the DTV channel shifts from streaming channels to four traditional broadcast channels delivered OTA and through cable systems. At 8 p.m., the station broadcasts a traditional SD channel plus an HD channel. Then, from 11 p.m. to 8 a.m., it broadcasts an SD channel with a heavy data push for delivery of NVOD to the LAUSD campuses.

To handle these complex tasks, the station chose the 28-channel Omneon SPECTRUM media server system, along with Sundance Digital’s Titan automation software. Datacasting is accomplished with the Triveni Digital Skyscraper system, coupled with Sundance’s Seeker asset-management system, which provides the VOD interface and ordering system.

Teachers can now browse the digital repository of the KLCS and LAUSD media libraries. These include not only video and audio, but also PowerPoint presentations, lesson plans and other resources. Low-res thumbnails of available content are available for preview over the internal network or a dial-up modem. Once a teacher selects and requests digital content, the high-resolution version is datacast to the school’s edge server for future playout.

The Omneon server enables the implementation of a unique file and codec structure that allows all content to be treated as data within a fully digital environment. What makes the system unusual is the way it allows engineers to separate studio and edit content, play-to-air material, streaming channels and other assets into different volumes on the same server. The server acts as a hub for I/O devices, with different codecs pointed directly at specific folders. The facility’s automation system only sees the material relevant to it.

Media assets are recorded directly to the server and, depending on where the content needs to go, the codec is pointed at the appropriate folder. For editing, the codec points to a specific folder that is automatically swept into the edit SAN. If it is a live-to-server show, the codec is pointed to a folder that is swept into the ingest server for play to air. Multiple encoding formats (MPEG, DV, etc.) are supported by matching the most efficient encoding scheme to the content. For the reverse path, files are loaded directly from the edit bays to a play-to-studio folder for integration into a show. A DNF controller operates the server as if it were a tape deck.

The station’s choice of editing systems, Pinnacle’s Liquid Edition and Liquid blue NLEs, was influenced by several factors. First, due to the nature of the facility and its mission, the NLEs had to be able to mix different compression formats on a single timeline. Second, they had to be compatible with the firewire drives deployed in the field cameras. Last of all, the station wanted easy-to-use solutions with enough horsepower to accomplish higher-end effects in real time. The editing systems met those goals.

The automation system that controls content flow, Sundance Digital’s Titan, features an automation architecture that enables GUI-based, dynamic reassignment of playlist control. It performs station asset management and also serves as the teachers’ interface for ordering NVOD assets. The automation oversees near-line archiving for play-to-air material with an Avalon archive, and an Intelli-Sat recording manager handles the recording of incoming satellite feeds.

The Avalon archive folder system features direct API control by the automation and a data-management hierarchy using XDSM folders. Assets from the edit bays, studio and VOD system are auto-archived with this.

The near-line archive supplied by Grande Vitesse Systems (GVS) consists of 22TB of Nomadic storage and is expandable to more than 100TB without downtime. An LTO2 tape system is available for long-term archiving. The system provides a maximum level of fault tolerance and redundancy without sacrificing a lot of storage. Running on the GVS (multi-CPU routing), the system can dynamically reallocate volumes without interruption. The storage system has the bandwidth to handle SD and data, plus HD material.

Master control is primarily a Leitch facility. The equipment includes a Leitch NEO SuiteView multi-source display processor, an Integrator GOLD SDI router, an Opus master-control switcher, a DPS-575AV digital processing synchronizer, a 6800+ video and audio conversion system, 880 series stereo audio DAs, and digital clocks. A NEO modular infrastructure platform routes, controls and monitors the entire infrastructure. Leitch’s CCS Pilot and CCS Navigator allow engineering to troubleshoot problems, remotely if necessary, and quickly bypass the problem until repairs can be made.

The DTV transmission system uses a Dielectric 888 antenna for both NTSC and ATSC channels, an Axcera solid-state transmitter, TANDBERG encoding, MRC digital microwave and the Triveni datacast system. The Axcera transmitter provides signal stability as well as good SNR to the station’s coverage area. The Dielectric dual antenna eliminated the need for a separate tower for the DTV system.

The TANDBERG encoder is designed as a VBR system with N+1 automatic failover. It is used to encode the DTV stream and to transport the analog signal as STL. (Even the analog signal is digital until just before it is injected into the analog transmitter.) The station can employ a redundant MRC DAR Plus radio for STL and TSL applications. Using TANDBERG’s 6120 and 1260 systems, the stream at Mt. Wilson is ready for distribution to the transmitters. The microwave’s T1 circuit for the CCS system integrates the transmitter site into the communication system.

Since KLCS launched the new services in January, the facility has demonstrated that dynamic bandwidth allocation in a broadcast environment is a real-world solution. It also shows that integrating off-the-shelf solutions from a variety of sources and vendors can be successful and relatively easily.

A comparable fiber-based system would have cost $300 million to $400 million and taken years to complete. This entire project cost less than $6 million and took less than two years. As computer vendors begin delivering DTV data cards with computers, this type of solution could provide an opportunity for broadcasters to be more than just TV stations. It could allow them to become digital content-distribution centers.

Alan Popkin is KLCS’ director of technical operations and TV engineering.