The Future of Video Servers, by Ross Summers

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Thomson Grass Valley Articles
The Future of Video Servers


by Ross Summers, November 15, 2006
Director, Next Generation Products, Grass Valley
When the Profile video server was launched in 1994, it was a genuine revolution in broadcast technology. For the first time systems designers had a source of instant access to a mass of content. Now it is inconceivable that any new playout or news system would be designed without a video server as the heart of its storage and playout system. Profile, and its competitors, made the best use of technology available then to deliver the performance required. Most important of them is that broadcast quality video is tyrannical in its real-time demands: you simply have to deliver the right picture every 25^th of a second, day in, day out. No other application has such a rigorous real-time regime. The K2 platform from Grass Valley represents the next generation of video servers. Essentially it takes the current best-of-breed IT solutions and blends it with the same high-quality video engineering that has kept the Profile as the market leader. The result is a video server platform that is truly scalable, firmly in touch with current market needs, and very cost-effective. FORMAT AGILITY If we consider the requirements of a video server for the future, the most obvious point is that it must handle equally well the current library of standard-definition content and the increasing stock of HD content. As a station moves to HD, it should be capable of playing any video, whatever its original format. To a large extent, the K2 media server does not care about the format of the content it stores; it is regarded simply as a data file. It will store video and audio as elementary files, and supports Quicktime and MXF files – it really does not matter, as it is a true, data-centric server. There are two different K2 media clients: one for standard definition, and one that supports the transition to HD. The important point to bear in mind is that the client is, fundamentally, a video and audio I/O device, which sends/receives data from the server and its storage. The server manages the file system, contains an ftp engine and manages Quicktime, MXF and CIFS devises. The standard-definition K2 media client has four bidirectional ports, which can be assigned as either inputs or outputs dependent upon the application’s requirements. The I/O is standard SDI, supporting DV and MPEG formats, at data rates from 2Mb/s to 25Mb/s (with an option for 50Mb/s). Provided they are at the same frame rate, all supported formats may be combined in the same timeline for seamless back-to-back playout. This is invisible to the operator at the time of playout: you select the content and the K2 sorts out the necessary format conversions automatically. As well as eliminating a layer of equipment, this also eliminates a source of risk — it does not matter if you select a DVCam clip at 25Mb/s immediately followed by an MPEG clip at 18Mb/s — the playout will remain seamless. The other K2 media client is known as the agile version, for reasons that will become clear. It supports all the standard-definition formats, plus both 1080i and 720p high definition MPEG formats, I-Frame and LongGop at up to 100Mb/s. The same operational considerations apply. You should be able to select the content without worrying about format. This is the case. The K2 agile media client allows you to combine any formats on the timeline for seamless playout – even switching cleanly between 720p and 1080i. Built-in up, down and cross conversion is provided, together with user-definable rules on aspect ratio conversion to accommodate legacy 4:3 material in HD programming or 16:9 HD content into 4:3 standard-definition services. Equally important to the agility of outputs is the scope for scaling the server system, from a handful of channels to a hundred or more, with storage capacities, even in HD, to match. While a number of server manufacturers profess to offer scalability, in practice it means choosing from a number of preconfigured sizes. If your requirement does not fit precisely into one of these preferred sizes, then you may end up with an over-specified system at an inflated price. STANDARD ARCHITECTURE Two fundamental technologies are available for the design of video servers, fibre channel or Gigabit Ethernet. Fibre Channel has traditionally been the choice of high-end servers (Profile included), but now Gigabit Ethernet offers a price and cabling advantage. So in line with the Grass Valley K2 media server’s use of IT technology, it is entirely based on GigE for connectivity clients, file transfers and control. It is just as good as Fibre Channel, but less expensive and by using one network technology, simpler. It is an obvious point that, in a typical IT client/server system, the clients would be attached to the server via a network. Why should it be any different in a video client/server application? And what network infrastructure is better understood or simpler to implement than Ethernet? Ethernet now runs at gigabit speeds, which provides the necessary bandwidth for the application (and 10 gigabit Ethernet is on the near horizon). It is well proven, reliable and cost effective. The problem with gigabit Ethernet is that, by itself, it does not provide the bandwidth management necessary to guarantee real-time performance. That is where Grass Valley’s specialist design team comes into its own. Built into each K2 server is what we call an iSCSI offload engine. This manages the flow of information across the network, using the iSCSI protocol. The iSCSI offload engine uses specially developed microcode that is extremely efficient, and allows the K2 server to drive the Ethernet at remarkable speeds, passing content at around 100MB/s – that is 100 megabytes a second. With the iSCSI overhead, that is close to the theoretical maximum capability of gigabit Ethernet. And each K2 server has two offload engines, so it is capable of driving gigabit Ethernet two wires at that rate. Each server utilizing iSCSI in this fashion results in a solution that is precisely scalable and deterministic and you can add clients up to 100 channels or more If you have a 20-channel system and you need to expand, you just add another client. Some other manufacturers would require you to add the capability in large channel chunks, and large RAID systems, representing a disproportionately large investment – arguably, that is not true scalability. Equally, storage can be built up in modules to the configuration needed. The user gets to choose the RAID level, the degree of redundancy in controllers and drivers, and of course, the capacity. There is virtually no limit on the capacity of storage. For very large back-end systems a SAN can be employed, and here fibre channel is the appropriate interconnection between RAID and server, something that could be installed and forgotten. The clients would still be connected over gigabit Ethernet via iSCSI The coming of HD will really soak up server capacity and bandwidth, which is why the development of a new server architecture is really important. At IBC2005 one of the K2 demonstrations was a 24-channel HD system, playing out 16 simultaneous 100Mb/s HD streams. CONNECTIVITY In K2 Grass Valley has also implemented CIFS, the common Internet file system, a very widely supported protocol. In effect, it makes the whole of the server look like just another disk drive to applications that support CIFS. It means that Apple’s Final Cut Pro, for example, can sit directly on the server network. Manufacturers have talked in the past about seamless access, but this really is. There is not a single change to the familiar Mac or Final Cut Pro user interface. The K2 server – or that part of it available to the editor – looks just like a directly attached disk, and the gigabit Ethernet provides more than enough bandwidth even for HD editing. Desktop editors from newsroom systems, too, can access content using CIFS and gigabit Ethernet. At the risk of repeating myself, these are well understood and proven technologies, and implementing them to access a server such as K2 is a simple matter. An API is provided for third-party manufacturers, but the need for specialist development is kept to an absolute minimum. A number of server tools grouped together under the name AppCenter are also included as part of any K2 server. This includes the ability to create and trim clips and create playlists, useful as an absolute fallback in the case of automation failure. Another useful built-in tool is a time-delay. With no other equipment whatsoever K2 can provide a time-delayed transmission of anything from a single event to a 24-hour channel. AppCenter also provides for the management of the server, for example providing partitioning to create a number of virtual servers within a single system. This could be useful to provide secure walled areas for different channels working off the same server, or to present a work area for directly attached editors. Because these management tools also use the same gigabit Ethernet for connectivity, there is no need for a dedicated control computer at the server. It could be anywhere, even – given appropriate firewall protection – at a remote location, connecting over an IP circuit.