Four layer facility model

Analysis, discussion and design of a BOC infrastructure and workflow can be simplified by abstracting the components into a four layer conceptual model

Broadcast engineers always have had to deal with maintaining 100 percent reliable real-time signal distribution. Any hit, no matter how small, will impact an on-air broadcast. The technological complexity of this can occupy an engineering career. Yet today’s broadcast operations center (BOC) has exponentially increased in complexity with the addition of IT technologies.

Understanding signal flow, production workflow, resource interdependencies and application interaction spans numerous technical disciplines. No one person possesses all the requisite skills and knowledge necessary to know everything needed to design and maintain a technology integrated BOC.

BOCs are transitioning to file-based content transfer using a networked infrastructure. Previously dedicated islands of resources, interconnected by baseband signals, are now required to co-exist in a multi-format file-based interoperable-networked environment.

How does and engineering organization approach this challenge? Analysis, discussion and design of a BOC infrastructure and workflow can be simplified by abstracting the components into a four layer conceptual model. These are the physical, media network, application and security layers.

The physical layer

No matter how digital the TV business gets, there will always be analog technologies in a BOC. On the fundamental layer, there will always be AC power. Any kind of content dissemination, over the air, cable, satellite, mobile phone and even the Internet, will use a carrier frequency of some sort with various modulation techniques to represent information.

Video and audio baseband digital signals are uncompressed essence and subject to real-time performance resiliency constraints. Analog NTSC will have to be supported until the turnoff date.

The media network

A BOC media network is neither a home PC network nor an IT network. File transfers must happen reliably and in a timely manner. File sizes are routinely measured by gigabytes.

Ingest and playout are the gateways of the real-time physical layer into the compressed essence IT domain. Once on the media network layer, files are the principle unit of information transfer through the production process.

A major benefit is realizing faster than real-time file transfers. However, this is a challenge with HD content. If a file is transferred at four times in real time and it fails, it can become difficult to move a day’s worth of content to a playout server. Retransmission is often not a viable option.

Among the components of a media network are the Cat 5 & 6 cables that connect switches, routers and bridges. Storage systems measured in terabytes with automated tape libraries implement hierarchical storage management systems. Content back-up strategies must be developed based on risk and access need.

Video formats such as MPEG, DV, AVC and VC-1, along with AES, MADI or AC-3 and Dolby E digital audio streams, may have to be supported. This broaches the issue of transparent file interoperability and transcoding artifacts.

GFX format interoperability is particularly challenging in that GFX vendors have built islands of technology. Some vendors have addressed this by designing equipment that converts file formats on the fly transparently in the normal production workflow. No extra manual conversion step is necessary.

The application layer

Having to restart an application is bad. Having to reboot a computer or recycling power is not an option when a station is on the air.

Compute platforms interface media networks and applications layers. Although built with PC boards and chips, 90 percent of a computer lies in firmware, software and the OS. For this model, computers part of the applications layer will be considered.

Nondeterministic performance is unacceptable. Software and platform operating systems must run flawlessly.


Restricting physical access to buildings, rooms and equipment has been the primary method of maintaining security at broadcast facilities. Show your badge and you’re in. Is this still sufficient?

That disgruntled employee, who didn’t get promoted, might be tempted to get even with a little surprise insert while you are on the air. Do you want to be responsible for something far worse than the Super Bowl Nipple Gate incident? How will you know who did it?

Physical access limitations are not sufficient. Virus scans and span blockers used in a home network are inadequate for use in a BOC alone. Firewalls and ACLs will not fully secure a BOC. Passwords can be broken. How do you deploy intrusion detection systems (IDS) and intrusion prevention systems (IPS) so that they are most effective?

Rights management is a security issue. Copyright clearance for broadcast and processing for consumer use must be facilitated by the infrastructure.

Greater than the sum and products of the parts

If numerical values of complexity could be ascribed to each layer, the total BOC complexity is the essence layer raised to the media network then raised to the application layer raised to the security…probably a number larger than a googolplex!

BOC Complexity = ((((Essence) ^ Media Net) ^ Application) ^ Security)

Emphasis must be on program and project management. A budget and timeline alone are not sufficient. No one person can know all that is needed to be known, about all technologies in a BOC. Solid planning, documentation and project management will prevent the effort form crashing, burning and relive stress. Teamwork and planning is key.

A signal flow example

A signal enters the BOC via, satellite and fiber, originates as a studio production or from a VTR. For the sake of discussion, let’s assume the essence is in a baseband state. By definition this content is on the physical layer. As it is ingested, compression occurs and now the signal, with its associated metadata, is content in a file format. At this point it enters the media network layer. All movement of the content file is over networked switches and routers, on CAT 5 cable and stored on disk arrays. To ingest, transfer and playout the content, a newsroom control system, media librarian or other control application running on a computer is used. This is an action on the application layer. Determining who has the authority to perform any or all these functions can be facilitated through login scripts, user roles and group memberships, each an element of a security layer methodology.

Where none have gone before

Seems pretty simple doesn’t it? But drill down at each step on each level. Many successful careers have been built in broadcasting on the physical layer. This is traditional broadcast engineering and it is known how complicated this can get. The laws of physics cannot be altered.

A new engineering discipline is emerging. Technology is in its infancy. Media, in particular HD video, is extremely demanding and pushes technology to its limit and beyond. Each of the four layers requires expertise gained after years of school, training and real world experience.

In the next series of newsletters, each of the infrastructure layers will be described in more detail.


Moving toward a dual-infrastructure facility, By Stan Moote, Steve Sulte, Todd Roth and Nabil Kanaan Sep 1, 2004

Broadcast Engineer’s Reference Book, Ed. by Tozer, Focal Press, 2005

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