Have you ever wondered how a TV News station like CNN, BBC World or Al Jazeera manages to keep a rolling news channel on air and up to date, 24 hours a day? Of course you need great reporters, presenters and producers, but you also need a first rate technology infrastructure and an engineering team with the skills to keep the machine running.

This simple introduction to the architecture of a Digital TV News Production facility will explain the key functionality and discuss some of the design decisions that must be taken along the way.

Technology keeps moving forwards. Ten years ago, videotape was king. Material was recorded, edited and played to air from VT. But tape systems are expensive and inflexible, and have largely been replaced with server-based systems. The earlier video servers were standalone boxes that recorded and played back from internal disk drives. But that too has changed; the current model is one of centralised shared storage.

1. Ingest, Storage & Playout

The modern Server is not normally a single unit. Most are modular in design so that they can be scaled to suit different users' requirements. In this article I shall use Video Server to mean a module with video ingest (record) and/or playout ports and internal codecs to convert between the Real Time Format (High or Standard Definition Digital Video - HD- or SD-SDI) and the compressed File Format (MPEG2, DVC-Pro, etc). And I'll use Media Server to mean an asynchronous file server for moving File Format material around the system, usually by FTP. Frame 1 shows the starting point for any Digital News Production system: some ingest ports, some playout ports and somewhere to store the material.

You'll need enough ingest ports for all of your Agency Feeds, (Reuters, Associated Press, etc), your outlying Bureaux, incoming lines and tape ingest. (We're not completely tapeless yet - in a News channel, you must be able to ingest newsworthy material from whatever source it arrives in). Playout ports get used up even faster. A single on-air stream will often be configured to use 5 playout ports - A&B Main (the output), A&B Backup (the reserve output), and Preview, (to check material before airing it. As a rule of thumb, expect to need 1.5 to 2 times as many playout as ingest ports.

Most facilities are built using centralised storage, typically a large RAID Array configured as a Storage Area Network, or SAN. A SAN is a set of Fibre Channel Fabric Switches with no single point of failure. The SAN must provide enough bandwidth to allow all ingest and playout ports to operate simultaneously, and enough spare bandwidth to handle an agreed number of simultaneous asynchronous file transfers. All manufacturers will tell you their storage is scalable. Some may be believed - be careful!

2. Edit Stations

Commissioned material might arrive on tape ready for transmission, and need only be ingested into the system prior to playout. But most news material comprises agency feeds or rushes from your field cameras that will need to be selected, edited, and voiced-over before tranmission. So you need to add some Edit Stations to the basic system:

There is no need to move video material to the Edit Stations - it is already there. The Edit Stations are clients of the SAN, and share the storage with the Video Servers. This means that media can be edited while it is being ingested. For example: one ingest port is recording a press conference or Presidential address, while one (or more) Edit Station is cutting highlights from it and publishing them back to the storage for immediate transmission. Try doing that with a conventional videotape based system!

3. Digital Archive & Media Network

So far, we can ingest, edit and play to air, which is a pretty good start. Most of the material we ingest can be deleted when it is no longer news-worthy, to clear space on the storage. But some material is too valuable to throw away. You won't need it every day, but you will need it eventually, to re-broadcast or repackage to sell on. It's a retrograde step to dub it back to videotape and store it in a tape library, but we don't want it taking up expensive space in the SAN storage. The answer is to install a Digital Archive.

The Digital Archive might be a large robotic data tape library, or it might simply be a substantial area of RAID storage optimised for packing density rather than instant access. The key point is that the material is stored in its ingested file format. It is not returned to linear format. A typical Digital Library will have its own SAN (the Archive SAN) accessed via dedicated Archive Servers.

The two SANs are not connected directly. Instead, a separate Media Network is established (using industry-standard Gigabit Ethernet hardware). Media Servers on the On-Line SAN use FTP (File Transfer Protocol) to route material to/from Archive Servers on the Archive SAN, via this Media Network. The reason for this apparent complication is simple enough: the Archive system and the On-Line System usually come from different manufacturers. Interfacing is then best done via an open architecture industry-standard layer.

4. Alternative Architecture using the Media Network

The Media Network layer provides the means for moving material quite freely, for example to remote sites (FTP over WAN). Sometimes, the Edit Stations will access the On-Line Storage via the Media Network instead of by direct connection to the SAN. This architecture is most likely to be used if the Edit Stations and the Server & Storage Systems are from different manufacturers.

To recap - we now have a system capable of ingesting, editing, playing to air, archiving and retrieving materials. For a small, single-channel News Station nothing else is absolutely necessary, except the usual graphics, channel branding and, if required, automation. But above a certain size, this changes.

5. Proxy Operations - Browsing the Media

If the Station employs a large number of Editorial and Journalist staff, they are all going to to want access to the Media. However, it is expensive and unnecessary to give everyone access to broadcast quality pictures, especially in an HD station. Instead, you can install conversion servers to create low resolution 'proxy' copies of the material, at internet quality or a little higher.

Material is sent to a conversion server which produces a lo-res copy. This is then stored in a dedicated RAID Array. The lo-res 'proxy' material can be viewed, simultaneously, by a large number of users on inexpensive office PCs or laptops, or even from home, using standard web browser technology. As these proxies take up very little space, they need never be deleted, even when the hi-res material is archived. Thus is it possible to browse all on-line and archived media by proxy, which is a huge benefit to Production.

6. Proxy Operations - Browse Edit & Publish

Most News editing is simple cutting. This can be carried out by a journalist working on the lo-res proxy copy, using a simple workstation. This releases the hi-res Edit Stations for more sophisticated craft work. When a journalist has edited a package in lo-res, the resulting 'Edit Decision List' (EDL - basically a list of in and out points) is sent to a Conform Server. This dedicated server accesses the corresponding hi-res material and applies the same set of instructions to it, creating, or 'publishing' a new video clip. It works because the lo-res proxy is an exact match for the hi-res material.

Proxy operations are not limited to browsing and editing. In some systems, the proxy is also the master for all Archive search and retrieval operations.

This description is one of many ways of achieving more or less the same thing. In some systems, both the lo-res and the hi-res files are produced by the ingest server. In some, the lo- and hi-res versions share the same storage. In some, the Archive is hi-res only, while some will archive the entire 'asset'.

When designing a News Production facility, the important thing is to start from a Requirement Specification. With the help of a specialist Broadcast workflow consultant, decide exactly what you are trying to achieve before approaching any manufacturer. That way, you reduce the risk of being sold a pile of inappropriate technology.

Finally -

This introduction has been concerned only with basic Media Workflow through a Digital News Production facility. We have not dealt with Automation or with Newsroom Computer Systems, major components, both, of any real Digital News Production system. Still, I hope I've been able to give you a glimpse of the well-oiled machine behind the screen.