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Home-Building for HDV

Sep 1, 2004 12:00 PM, By Steve Mullen

How one editor specified his own system—from CPU to GPU—to optimize its HDV editing performance.

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Now that hdv is a viable production format with many associated editing solutions, I decided it was time for me to spec my own HDV editing system. Much has changed in our video world since March 2001, when my “Building a Better NLE System” article appeared in Video Systems. One obvious change is that realtime effects are typically generated by a computer's CPU — not by specialized hardware on a PCI board. Both Macs and PCs now routinely work with a half-dozen SD streams. This change forces you to look carefully at the hardware power of the platform you own. To maximize realtime capabilities, you need to keep your computer up to date. That means not only the fastest processors, but a maximum-speed motherboard and maxed-out RAM. Moreover, if 3D effects are generated by a graphics processing unit (GPU), you must be certain that not only is the processor super-fast, but also that it has a lot of very fast RAM.

The other huge change since 2001 is the increasing use of online NLE systems for editing HD. As you might expect, HD puts enormous demands on every component of your computer. So much so that at this point, I'm going to consider only the demands of what might be called HD-lite. This, of course, is HDV in its current 720p30 implementation. (If 720p24 were to be released, it would require about the same computer power.) Each frame of 720p has about twice the pixels of an NTSC frame. That tells you that within the computer, two times more data must be processed.

If you are working with a native HDV solution (KDDI Media Studio Pro, Sony Vegas 5, Ulead MSP 7, and Premiere Pro with MainConcept), in addition to the computing power required to render effects, the computer must have the power to decode each HD MPEG-2 frame. Each frame is twice as large as frames decoded when you play a DVD on your computer, so not only does a computer need to decode MPEG-2 rather than decompress DV25, it must do so with two times more pixels.

Thankfully, with native HDV solutions the disk requirements remain the same as for DV25. That means a 7200rpm non-RAID will be fine. However, if you want to work with a non-native solution like Premiere with Aspect HD, you'll likely want a RAID.

Choosing a CPU

While I'm well aware that processors from AMD offer great performance at a low price, I chose Intel for two reasons. First, some vendors obtain maximum performance by coding for the Intel architecture. Second, when NLE vendors qualify computers, Intel processors are typically qualified first. So the questions for me were which Pentium 4 to use, and how fast does it need to be. The latter question is always easy to answer. Choose the fastest you can afford. If, however, you are value-conscious, choose the second-fastest processor of those currently available. When writing this in early June, the fastest P4 had a clock rate of 3.4GHz. Thus, to minimize cost, I went with a 3.2GHz P4 for my new NLE system.

You may have noticed I switched from talking about the “fastest” to talking in terms of “clock speed.” That's because other aspects of a processor performance affect how fast it is — for example, the size of the on-chip cache. Intel has a special version of its 3.4GHz P4 — the Pentium Extreme Edition — that has an L2 cache that's twice as large as that of the typical P4. While this clearly yields a super-fast P4, it bumps the chip's cost to almost $1,000 — so I ruled it out.

While researching this story, Intel released the P4E (not the same as the Extreme Edition) that uses the Prescott “core.” (Core refers to the guts of a chip.) This Pentium replaces P4s that use a Northwood core. The new Prescott, like the newest Northwood processors, features Hyper Threading and supports an 800MHz front side bus.

The Prescott runs hotter than the Northwood because it has 125 million transistors crammed into only 112 square millimeters instead of only 55 million transistors within 146 square millimeters. This is a negative for laptops and small form factor computers. But on the plus side, the Prescott includes an enhanced instruction set that Intel calls SSE3. The new instructions support video encoding, graphics, and thread synchronization — all capabilities we care about.

Motherboard chipset

Once the CPU has been chosen, you must select the motherboard chipset. Once again I decided to go with Intel. Intel offers two chipset families: the 865 (Springdale) and 875 (Canterwood). The more expensive 875 is designed to support costly error checking and correcting (ECC) RAM, as well as the option of super-fast but expensive Rambus memory.

As neither error checking and correcting nor Rambus memory is critical, I chose the lower-cost 865 that appears in three versions: 865P, 865PE, and 856G. The 856G features a built-in graphics function Intel calls “Xtreme Graphics 2.” The only thing extreme about it is how slow it is. However, this feature does let your computer run without an AGP board, which might be important if your graphics board were to suddenly fail. The choice between the 865P and 865PE is a simple one, as the 865P does not support an 800MHz front side bus. So that means we want either an 865G or an 865PE chipset.

Before moving on, I need to mention that you have other options. Intel is now shipping two new chipsets called Grantsdale and Alderwood that will, among other features, support a PCI Express bus (not the same as PCI-X) that replaces both the PCI and AGP buses. Both chipsets will support Intel's new “Socket 775” processors. Future Intel processors with clock speeds greater than 3.4GHz will be released only in Socket 775 versions. Socket 775 will come with a new BTX or MicroBTX motherboard (possibly requiring a new power supply and case) as well as faster RAM (DD2) and a PCI Express graphics card. The very first, and very expensive, computers using these chipsets are now shipping.

Alternately, for workstation performance, you can go with an Intel I860 chipset that supports one or two Intel Xeon processors. Expensive — about $5,000 with dual 3.2GHz Xeons — but super-fast.

A key feature of the 865/875 chipsets is that they support Double Data Rate (DDR) memory. Put simply, while each chip is clocked at 200MHz, it delivers data twice per clock tick for a data rate of 400MHz. Because two DDR400 RAM chips are accessed simultaneously, the motherboard's front side bus is set to 800MHz. Therefore, you'll need to choose PC3200 RAM and buy it in equal-size pairs.

PC3200 refers to the sustained bandwidth of each RAM chip. (Aggregate memory bandwidth with DDR is a whopping 6.4GBps because each chip delivers 8 bytes twice per clock cycle — and two chips are accessed simultaneously.) Bandwidth, however, is only one measure of RAM performance. The other factor is RAM latency. A DDR400 chip has a cycle time of 5 nanoseconds. So, from the time a location is accessed, how long until the data are available? This delay is column access strobe (CAS) latency. You can buy RAM with a CAS of 3.0, 2.5, or 2.0 nanoseconds. Naturally, the shorter the latency, the more expensive the RAM. Benchmarks show that for MPEG-2 encoding, low-latency RAM is about 2 percent faster. If you are building your own system, I recommend the Corsair (www.corsairmicro.com) “Value Select (Dual Pack) 184 Pin 1GB (512MBx2) DDR PC-3200” that provides a cost-effective CAS of 2.5.

Graphics board

There are three criteria for selecting a graphics board. First, does it support DirectX 9.0? This is critical because included within DirectX 9.0 is a function called DxVA. This function allows applications that support MPEG-2 to access hardware within the GPU. One function, an inverse discrete cosine transform (iDCT) supports MPEG-2 decoding; the other, a discrete cosine transform (DCT), supports MPEG-2 encoding. One hopes that native HDV editing software in the future will make use of both functions to increase performance. ATI Radeon GPUs with model numbers 9600 and above support DirectX 9.0. The latest chips from Nvidia and boards from Matrox also support DirectX 9.0.

The second criterion is the amount of GPU RAM. RAM size can be important when applications buffer multiple frames of video to support smooth playback. The minimum you will want is 64MB; 256MB is more than enough.

The third group of criteria covers a number of considerations: 3D edge filtering applied to video to increase quality; width and speed of the path between the GPU and GPU RAM; maximum supported monitor resolution; supported monitor color depth; maximum monitor refresh rate; number of monitors; type of connection (VGA, DVI, analog component, HD SDI, S-Video, composite); support for RGB, NTSC, and HD video output from an overlay; and the size of the overlay buffer (NTSC or HD). Complicating the understanding of these issues is that almost all discussions of graphic boards consider video to be NTSC resolution from DVDs and high-resolution images to be from 3D games. Moreover, NLE packages do not yet define specific requirements for the HD graphics board.

I wanted to keep the total system cost under $2,000, so an ATI 9600XT with 128MB of DDR RAM became a cost-effective choice. The 9600XT (www.ati.com/products/radeon9600/radeon9600pro/index.html) has VGA and DVI-I connectors, plus an S-Video connector. Independent resolutions and refresh rates can be selected for any two connected displays. The maximum resolution is 2048x1536 at 85Hz. An optional DVI-to-VGA adapter allows connection to a second VGA monitor, while an optional adapter provides HD YPrPb component output. (Both plug into the DVI connector.)

Computer case

I'm tired of beige and black tower boxes. I wanted a case that looked like it belonged in the 21st century. To increase the ease of any future upgrade, I also wanted a case that used an industry-standard motherboard (ATX or MicroATX), which meant I had to reject the Shuttle SB65G2 XPC (www.shuttle.com/index.html) and my favorite, the FIC Ice Cube IC-VL67 (www.fica.com).

My choice was the Antec Aria (www.antec-inc.com/us) that accepts a MicroATX motherboard, an AGP card, a memory-card reader (CF I/II, MS, MS Pro, SM, SD, MMC, MicroDrive), and a 5.5in. optical drive. It has two free PCI slots (a fan is usually placed in its third slot), and it can hold up to three hard drives (system drive plus two RAID 0 drives). The case includes a 300W power supply and measures only 7.9"×10.6"×13.2". With its cool, indirect blue LED lighting it looks fantastic.

Motherboard

If you have a monster computer, you may be surprised that I would consider a system with only two PCI slots. The reason this is possible is that today's ATX and MicroATX motherboards provide nearly every function. These functions include FireWire 400, USB 2.0, 10/100 Ethernet (and some even offer Gigabit Ethernet), six-channel analog audio, 5.1-channel digital audio, support for ATA and SATA drives, plus support of hardware RAID.

For the Aria case, the only MicroATX board that met all my requirements was the 865M01-G-6ELS from Foxconn (www.foxconn.com). It offers these features: DDR400 RAM up to 2GB; UltraDMA100 for up to four devices; two Serial ATA 150 ports; an 8X AGP slot; three PCI slots; PS; COM; LPT; 10/100Mbps LAN; USB 2.0; IEEE 1394; 5.1 analog audio output.

Disk drives

The value proposition in the hard disk drive market is constantly changing. If I were building a system with RAID 0 for video media, I would connect the two RAID drives via SATA. The OS drive (and audio media drive) would be connected by parallel ATA.

Naturally, you will want a DVD/CD reader/writer. Depending on the brand, you will have to choose its type: -R/-RW or +R/+RW or ±R/±RW, speed, and now single-layer (4GB) or double-layer (9GB). Because -R/-RW media is compatible with more DVD players and blank media is less expensive, I prefer it. However, if you and your customers own late-model players, +R/+RW should prove acceptable.

Display

Obviously, you'll want either a 16:9 aspect-ratio display or a 4:3 screen to which a 16:9 window can be mapped. According to Microsoft, to play Windows Media 9 1080p DVDs, you need a 16:9 WUXGA (1920×1200) LCD monitor. Unless you have 20/10 vision, to read text you'll need a very large and ultra-expensive display. To play Microsoft WM9 720p, or HDV 720p, you need a display that can handle 1280×720. Thus, you'll want a WXGA (1366×768), WSXGA+ (1680×1050), or WSXGA (1600×1024) monitor. These offer aspect ratios of 1.78:1 (16:9), 1.60:1, and 1.56:1, respectively.

Cost

Naturally, cost is a function of where you buy parts. To make shopping simple, I used the Newegg.com website (www.newegg.com) because the company offers low prices and has a positive reputation. Table 1 shows the cost of my “Steve 2” design.

Make vs. buy

Building your own system has three advantages. Because you chose the components, you get maximum control over performance and price. Second, you built it, so you understand it. This makes it simpler to fix and upgrade. Lastly, there is the pride of doing it yourself.

You will note I did not claim that lower cost is an advantage. That's because companies like Dell have such control over component pricing, they typically can at least match the real cost of a home-built system. By real cost, I mean the included warranty, support, and resale value. I gave my last home-built to a relative because the going price of “Steve 1” on eBay was so low.

With a list of desirable components, you can go online and build a commercial system that matches your requirements. However, if you want a particular graphics board or optical drive, you might not be able to get an exact match. For example, Dell belongs to the +R/+RW group and so does not sell -R/-RW drives.

Companies like Dell also offer an option you cannot provide for yourself. That's a custom-built laptop. Looking over the key components in my design, I realized that I could specify these parts in a commercial laptop. Portability and an integrated display matched my needs perfectly, so I took the list of components and spec'd a Dell Inspiron 9100 notebook that had a price of $2,300. (See the right column of Table 1.)

The Inspiron's ATI Mobility 9700 offers VGA and DVI-I connectors, plus an S-Video/composite connector. The screen is a 15.4in. WSXGA that offers a 1680x1050 resolution image. AC-3 digital audio output is available via an SP/DIF port. A PC/MCIA slot can accept a FireWire Direct card (www.firewiredirect.com/firewire/products/cardbus.shtml) that provides a FireWire 800 port to support an external RAID. This slot can also accept media readers. To easily obtain multi-channel analog output for surround-sound WM9-encoded DVDs, you will need to purchase a Creative Audigy2 NX External USB adapter (www.creative.com/products/welcome.asp?cat=2) for about $100. (This unit can also be used with the Steve 2 to provide SP/DIF digital audio input and output.)

Within a week of ordering the Dell Inspiron 9100, it arrived. I am not going to review the 9100, but here are my first impressions: big and heavy as expected; super-fast; great screen; plays HD WM9 DVDs without a glitch; the subwoofer really helps the sound quality; great keyboard and trackpad; very quiet. Average disk transfer from disk is 30MBps, which will readily support multiple streams of DV or HDV.

For those for whom portability or a trendy look are unimportant, you can take my list of components as a starting point. By choosing an ATX motherboard, for example, you can easily obtain hardware support for a four-drive RAID. And by choosing a tower case, you'll have plenty of room for a massive amount of storage.

Whichever way you go, you should find that a PC based upon this design will provide adequate power for both DV and HDV editing. Nevertheless, you can bet within a year I'll be back with a new list. By then the next generation of components will have arrived, plus we'll be working with 1080i HDV and its requirements for more computer power.

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