Just a few years back, the thought of digitizing video onto a personal computer was laughable. After all, full-motion, full-screen digital video–where every pixel of every frame of a 30-frame-per-second image is represented by a
computer-friendly "0" or "1"–is a huge amount of data to store and move. Yesteryear’s computers just weren’t up to the task. Editing broadcast-quality digital video on a home PC was about as far-fetched as composing a major symphony on a child’s toy piano.
Today, even inexpensive new PCs offer the raw speed and processing power required to store, edit and play digital video. A relatively painless $1,000-$1,500 investment will bring more raw computing power to your desktop than NASA used to land Apollo 11 on the moon in 1969. These days, raw power is the easy part. The challenge comes in getting the machine configured to do digital video correctly, without computer bottlenecks that cause chunks, blocks, artifacts and other digital video maladies.
There are enough combinations of PC hardware, software, operating systems and other goodies to fill several books. Instead of trying to cover it all in the next few pages, we’ll tackle some of the greater issues of capturing and editing digital video on a PC. Nailing down the specifics of your system is up to you, but these concepts should give you a good foundation to work from.
One of the key factors affecting video performance of a PC is "throughput." Throughput quantifies the amount of data a computer can consistently move from one component (hard drive, video card, etc.) to another. Since the combined video and audio data streams represent a massive amount of information, everything must be working well to play back video without dropouts or distracting hiccups. When any part of the computer fails to pass data quickly enough, it is called a "bottleneck." It only takes one sluggish component to bring a digital video computer to its knees. Finding and eliminating data bottlenecks should be a major priority for anyone getting into digital video.
Understanding how the key components of a PC work together is a good place to begin. We can divide the digital video editing computer into major sections, including processor, bus, RAM, permanent storage, video capture card and video display system. Each of these has an effect on the performance of the computer, though some are more critical for video applications than others.
The Processor Rides the Bus
At the very heart of the PC sits the central processing unit (or CPU), which is roughly analogous to the computer’s brain. The speed and type of processor is one of the first characteristics of a computer we notice (i.e., "It’s a 266MHz Pentium"). Faster processors result in faster performance in certain areas.
Some software may be happy running on a 133MHz Pentium or slower, but most of today’s software is coming out with greater minimum requirements. A 233MHz chip is considered entry-level, and 400MHz machines are becoming commonplace. Many motherboards (the main board containing the key computer chips and circuits) allow you to upgrade the CPU with a faster model. You may want to find out exactly how fast a processor your motherboard will support and how much an upgrade will cost.
Pentium, by the way, is a brand owned by Intel Corp., the largest and most popular CPU manufacturer. There are other fast chips out there that are cheaper, and some would argue, equal or better in performance. Pentium is the benchmark, however, and the other high performance chips are considered "Pentium-class."
A faster processor will net you a great performance improvement for processor-intensive tasks. These are operations that rely heavily on the computer’s main processor, instead of one of its many support chips or components. Combining two scenes into one during a transition (called "rendering" a transition) is a common example of a processor-intensive task used in digital video editing. Creating complex, overlayed titles or 3D animations also tax the processor heavily, as does applying video "filters" to a clip. The creation of transitions takes a lot of time with most digital editing systems, so investing in the fastest-possible processor you can afford makes good sense.
It’s important to understand that a faster processor will not fix a bottleneck occuring in another system component. You must eliminate those problems at the source.
The computer’s "bus" is the digital "highway" that carries data between all the various parts of the computer. The bus is part of the "motherboard" which you could equate with the central nervous system of the computer. It has slots and sockets where the processor, video card, RAM, modem, CD-ROM, hard drive and other components all connect. The motherboard houses the bus circuitry that allows all these components to work together to pass data back and forth.
Until quite recently, all PC busses were ISA busses, which means they chugged along at the same rate regardless of processor speed. Today, you can pick up a computer with a faster bus (PCI or AGP, for example) for improved performance. There’s no way to upgrade an existing computer to the faster bus without replacing the actual motherboard, but the performance increase this affords may be well worth it. And as long as you’re tearing out the guts of your machine, you might as well spend the additional effort to upgrade your RAM, video card, and anything else you can afford.
You can think of RAM (or random-access memory) as being your computer’s counter space or work area. When the computer opens an application or file, it usually loads its contents into RAM. The more applications you have opened at once, the more RAM is required. Making the computer operate with too little RAM is like asking a gourmet chef to prepare a six-course meal on three square feet of counter space and one eight-inch cutting board.
With RAM prices falling quickly, it’s easier than ever to afford adequate RAM for your computer. Most systems are sold with a minimum of 16MB, which is the minimum amount required to run Windows 95 and 98 operating systems. While 32MB of RAM once seemed like a lot of memory, for digital video it’s really not enough. A better starting point for video editing is 64MB, and doubling this to 128MB can offer substantial performance improvements in certain video editing applications. RAM costs on average about $1 per megabyte and as RAM prices fall, software developers are expecting today’s digital video computers to have plenty of memory. If you don’t keep up with this trend, your video performance will suffer.
One of the most important components in any digital editing PC is the hard drive (or hard drive system). It’s the digital storage tank and all the video and audio data in any digital production ultimately must find its way on and off a hard drive. If the drive or its controller isn’t able to move video data quickly enough, you’ll be guaranteed uneven playback. More important than access time (how quickly the drive can get to and begin reading a specific chunk of data) is sustained data transfer rate.
Many drives perform well when asked to read or write just a small chunk of data. Ask a drive to move a lot of data over the course of several seconds (or minutes), which is what’s required for video editing and playback, and the performance may not be so stellar. A drive’s sustained data transfer rate measures how much data it can transfer continuously, which is critical for smooth digital video editing.
Today, there are three main types of hard drive/controller combinations you can buy. The older and less expensive IDE (Integrated Drive Electronics) standard has served well for a long time. This has been upgraded to the much-improved Ultra DMA/33 (Direct Memory Access), which approaches speeds necessary for hobbyist-level nonlinear editing. The newer SCSI (Small Computer System Interface) standard costs a bit more, but can offer the best overall performance.
Though many people equate SCSI interfaces and drives with faster data transfers, those four letters alone aren’t responsible for drive performance. Instead of interface type, the primary factor in hard drive performance is drive RPM. The faster a drive is spinning, the faster it can access data and pass it to the controller. Drives turning at 7,200 RPM or higher are a must when working with higher data rates and better video quality. But faster drives also run hotter, and thermal recalibration–when the drive takes a brief break to adjust for changing temperatures–can interrupt the data transfer. This leaves blank spots and other anomalies that are definite no-nos for digital video.
Audio/Video (A/V) drives offer the added benefit of not performing this step while in the middle of a crucial file transfer. This isn’t to say that you must use A/V drives for video editing, but you may experience occasional breaks in playback for no apparent reason if you don’t. Countless thousands of people edit lower data rate video with standard, non-A/V drives every day, however, and relatively few have problems.
As with RAM, hard drive prices are experiencing a free fall. A/V drives are cheaper than ever, and most will keep up with the performance demands of home videographers. If you’re picking one out, you probably want to start with a SCSI A/V drive in the 4GB range. If you can afford it, you’ll never regret purchasing a drive with twice this capacity (or more). When it comes to video editing, you just can’t have too much disk space. SCSI devices require that your PC have a SCSI port. If it doesn’t, a SCSI card that fits into a slot on the motherboard can give the machine this capacity.
Video Capture Card
The video capture card is a critical piece of hardware for video editing. It typically doesn’t come with a stock PC, but a digital video editing system must have one. It, too, plugs into a slot on the motherboard. The capture card has video in and out jacks to take the analog images from the camcorder tape and "digitize" them, which turns the images from analog into digital 1s and 0s. It then compresses the data it so it fits in a reasonable amount of space and sends it to the hard drive for storage. If you are using a DV format camcorder, where the video is already digital, then the capture card transfers the data straight from the DV tape to the hard drive. The format the card uses to compress the video (called a "codec," which is short for compressor/decompressor) is one of the key elements that establishes the cost of the card and the finished quality of the video. Other things to look for include maximum capture resolution (640×480 is the minimum necessary for high quality full-screen output to videotape), 60-field-per-second capture, and maximum color bit depth (24-bit being the standard for high quality color reproduction).
Consumer-level video capture cards run the gamut in price from about $150 for the least expensive to $5,000 for the most expensive (for more details, refer to Videomaker‘s Video Capture Boards Buyer’s Guide, March 1998). Typically, the more money you pay, the larger the image and the greater the number of frames per second you can capture, edit and output to finished tape. Cards that create smooth, full-motion 30-frame-per-second video cost in the range of $350-$5000.
The Other Video Card
Not to be confused with the video capture card, the computer’s "display adapter" is the video card responsible for creating what you see on your computer’s monitor. In the grand scheme, this video card is rarely a source of bottlenecks leading to dropped frames. What it can do, however, is make for very sluggish screen redraws. A fast display adapter that supports high screen resolutions of 1024×768 or higher is preferred for editing video, as are color modes that will display thousands or millions of colors. Higher graphics resolutions virtually require a 17-inch or larger monitor as well. If you plan on spending much time in front of your editing system, you’ll find that a large monitor is very helpful.
Set It Up
If setting up a PC for video seems like an insurmountable task, take heart. There are lots of available resources to help you, including this magazine, Videomaker.com, Internet Usenet groups, online help files and other knowledgeable PC users. There’s also the option of purchasing a turnkey (pre-configured) nonlinear system, or having a computer vendor set up a system for you. Whether or not you build your own system, however, taking the time to really learn what’s going on inside your video-capable PC will help you understand how to fix it when it breaks down. And that’s information any PC-based nonlinear editor can use.