Videography - July 1997
SGI Revs Up Video and Networking with O2 and Octane
by Sheldon Liebman
Silicon Graphics isn't just a 3D company any more. With the recent introductions of the O2 and Octane workstations, the company's entire product line is very much at home in the video and entertainment industries.
For a number of years, SGI's highest end products have been used to move beyond 3D animation and into general-purpose video and film applications including compositing, special effects and non-linear editing. Now, these applications have moved into the mainstream with the O2 and Octane.
In a current advertising campaign, SGI is promoting a very usable configuration of the O2 for under $7500, a price level that has previously been reserved for PCs and Macs. At the higher end, the Octane can be purchased for under $20,000. Even fully loaded, the Octane tops out between $50,000 - 60,000.
The aggressive pricing on these products is a clear indication that SGI is serious about providing affordable workstations. The company is also being very aggressive when it comes to support for video and networking.
A Breath of Fresh Air
The O2 workstation is SGI's latest version of an "entry-level" system, although it's not completely appropriate to use that term on this machine. Powered by a MIPS R5000 or R10000 chip (running at up to 180 MHz), the O2 comes standard with advanced 3D graphics, powerful image processing and real-time video capability. Standard compression hardware and software provide non-linear editing capabilities.
One of the keys to the performance of the O2 is a design called the Unified Memory Architecture, or UMA. According to John Barco, O2's Product Manager, UMA "allows us to put many high end features into an affordable product." With UMA, all the memory in the machine is pooled into a central location. For example, "There is no separate graphics memory," says Barco, "but the bandwidth is very high between memory and the graphics engine." One advantage of this architecture for users is that there is only one type of memory to upgrade.
Standard networking support for the O2 includes 10BaseT and 100BaseT. Neither of these is fast enough for real-time video, but third party cards can solve that problem. Barco explains that support already exists for "ATM, FDDI, Fibre Channel and ISDN." Support for other networking protocols is in development both by SGI and by third party vendors.
Even in the base model, O2 has a lot of video processing capability. "A lot of the processing that's done with traditional video cards is on (O2's) I/O card," states Barco. By default, users can input and output video in Composite and Y/C formats. Optional hardware from Miranda Technologies, Inc. (St. Laurent, PQ, Canada) supports BetaCam or D1 input and output. Two channels of input and one channel of output are supported simultaneously.
Real-time M-JPEG compression and decompression is built into O2 with compression rates as low as 4:1. Dual UltraSCSI channels allow fast disks and disk arrays to be easily connected to the workstation. "If you want to stream uncompressed video," says Barco, "you can hang an array off it."
Other compression and decompression formats are also supported. MPEG1 encoding through software is included as part of the O2's Digital Media Development Kit. Playback is accomplished in real-time through the CPU. Apple's QuickTime and Microsoft's AVI formats are also supported and software is available to convert between any of these formats.
With support for all of these features, the O2 is a very powerful workstation for video professionals. The memory architecture and basic features meet SGI's goals of creating an affordable system that eliminates many of the bottlenecks associated with traditional computing and video production. However, the O2 is probably best suited for an off-line environment, as it doesn't have the sheer horsepower to do many complex operations in real-time.
Gentlemen, Start Your Engines
To rev things up to the next level, you need to use SGI's Octane. Powered by one or two R10000 chips running at up to 195 MHz, the Octane is designed to support projects like uncompressed non-linear editing and film resolution effects.
The Octane also utilizes a specialized architecture to achieve very high performance. In place of a traditional shared bus, this workstation uses a Crossbar Architecture. Rick Reagan, Digital Media Product Manager for Octane, explains that this multi-port architecture "is like the phone company uses. The processor sits on one port, graphics on another, the PCI64 bus is on another." The crossbar can dynamically and directly link any two computer subsystems, giving them unblocked access to a very high speed data path that supports up to 1.6 GigaBytes per second (GBps).
Given that uncompressed HDTV requires "only" 180 MegaBytes per second (MBps) of bandwidth, this architecture can theoretically support almost 9 simultaneous HD streams or over 50 simultaneous D1 resolution streams. At this year's NAB, SGI provided a stunning example of just how much bandwidth is available with this machine. At their booth, they were playing uncompressed HD resolution clips from the recently released movie "Volcano." According to Reagan, "We were pushing out 180 MBps and (the Octane) wasn't even breathing hard."
With this much bandwidth available, the biggest question may be how to get it from a storage device onto the screen. Of course, since the Octane (and the O2) can be configured with up to 1 GigaByte of system memory, it may be just fine to load it from disk into memory before playing it to the screen. For uncompressed D1 video, this would support clips of approximately 30 seconds from memory.
For more than that in a D1 environment, you can easily provide the bandwidth you need using a disk array. "The fastest drives we see today support approximately 10 MBps," says Reagan, "and you need 30 MBps for video, so you have to use a RAID or some other parallel process."
Getting the data from that disk array to one or more Octanes is not a problem given the extensive networking support available for this platform. Interfaces are available to Fibre Channel, UltraSCSI, ATM OC3, Serial HIPPI and 10/100BaseT Ethernet. In a departure from past practice, many of these interfaces were actually developed by SGI. Outside companies like Prisa Networks (San Diego, CA) and Essential Communications (Albuquerque, NM) also manufacture these products, but they now compete with SGI in this area.
When it comes to digital video, the Octane supports a multiple formats and multiple simultaneous streams. The top of the line option is the Octane Digital Video board, which provides two input and two output channels of CCIR-601 serial digital video. The video can be either NTSC or PAL and 8 or 10 bits. Many video-processing functions are also built into this board.
A built in color space converter moves images between RGB and YUV and includes a patent pending "constant hue hardware unit" to maintain quality even when converting extreme colors. There is also a real-time interface to the graphics texture system. This allows either a single stream of video and key information or two streams of video to be texture mapped onto a polygon. These real-time video textures can be used to create true 3D digital video effects.
The Octane also supports high quality video compression. An optional Compression board supports two streams of M-JPEG compression with ratios as low as 2:1. At this rate, many people consider M-JPEG to be "visually lossless." The board can be used either to compress video streams that are coming into the system or video that is already contained in memory (such as rendered frames). The Compression board has a direct connection to the Digital Video board so that two streams of D1 video can be independently compressed or decompressed in real-time.
Another feature of the Octane's Compression board is its ability to function as a Virtual DDR. Sequences of images on disk can be compressed, combined and stored on disk. Once compressed, the sequences can be played back at full resolution for display on the graphics screen or an external monitor.
How Fast is Fast?
One of the ways in which we can determine the practical speed of a system is to look at how we can use it. With the O2 and the Octane, SGI has created powerful, integrated solutions for many production and post-production applications. The Octane in particular, due to its dual processor capability and Crossbar architecture, seems to do just about everything we need. According to Reagan, it has "What If" speed. "When (the system is) fast enough, you try a number of versions of something rather than just settling for the first." It's nice to know we have that option.
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