updated 31 March 2003

 

Configuration of Non-Linear Digital Video Editing Systems, Part One
an article by Charles F. McConathy

In the first half of this article (check out the second half here), Charles outlines what you should consider for your editing requirements and provides an overview of hard drive options for video storage.

Even with the advent of faster processors, faster memory, faster busses, and faster disk drives, digital video still taxes the fastest computers. Unless the computer system is properly configured, some or all of these components can become a bottleneck, resulting in dropped frames, corrupted data, freeze ups, out of sync audio, or other problems. This article is written to help video editors avoid these issues and to make good choices when configuring a video workstation.

Choice of Computer:
Before selecting a computer one should consider the following:

The amount of budget available for computer purchase?
Do you need portability?
Will you be doing a lot of rendering?
Will you be encoding content for DVD?
Which operating system are you the most comfortable: Mac OS or Windows?
Which video editing software and hardware do you plan to use?
Do you plan to work with SD or HD video?

You will most likely want to go with a computer that supports the operating system and video editing software and hardware that you are the most comfortable with. And remember that computers are constantly changing. The computer itself will probably be the first component in your system to become outdated. In making a choice, go with a mid-to high-end model since it will serve you the longest. It is wise to upgrade or purchase a computer system as needed since they become outdated rather quickly. Don't look back: use it up. Remember that there will be faster computers around the corner; this does not mean the one you bought is not of value.

If Macintosh is your choice we suggest you consider a dual processor model. We believe you will keep a dual processor longer than a single processor, especially since many video applications are multi-processor aware. Mac OS X also exploits dual processors to improve performance. If your projects include a lot of rendering a dual processor is an excellent choice since it will save you a lot of time. The G4's "Altivec" or "Velocity Engine" also boosts rendering speed and accelerates Adobe Photoshop considerably.

Choosing a model that comes with a SuperDrive for DVD authoring is excellent. Adding a second monitor speeds the editing process since you can have longer time lines and have more pallets and bins open at the same time. Adding additional memory over what is normally shipped from the factory is another way to increase productivity.

If you need portability consider an iBook or a PowerBook. They both work well with Final Cut Pro. The iBook has a smaller screen and a G3 processor without Velocity Engine acceleration. The FireWire port of the iBook is excellent and works well with DV camcorders/decks and FireWire drives. The PowerBook has a larger monitor and faster G4 processor making it more productive.

Purchase an iBook or PowerBook for portability reasons, not as a substitute for a desktop workstation. Desktops are less costly to configure, especially when it comes to storage, and they readily support larger displays and realtime hardware.

If your budget is tight you might consider an iMac with a FireWire port. For additional storage use FireWire drives. Final Cut Pro works fine with an iMac. They are not as productive since they have smaller displays and slower G3 processors, but make a good entry level system. The new G4/700 iMac is much faster. The only thing is it does not have backside cache or allow you to install internal storage and you are fixed with the existing monitor which might be a bit small for some.

Many ask if it's worth it to upgrade an older Macintosh with a faster CPU. Generally our answer is no, especially when building a video editing station. Processor upgrades are expensive, consuming funds that could go toward a new computer with new warranty, faster drives, faster internal cache, speedier memory busses, etc. Improving the speed of a processor does not cure other internal bottlenecks. Upgrading a processor often creates a system that is unstable due to mismatched parts. We think it's best to repurpose the old computer or sell it, and take the upgrade cost and apply it towards a new computer.

If your choice of computers is a PC, consider a dual processor model that is housed in a cabinet with plenty of room for installing multiple disk drives and enough fans for good air management (needed to cool the disk drives).

Picking a motherboard with compatible BIOS and a VGA display card is very important. Not all motherboards are created equal. Many NLE software and hardware vendors list known compatible motherboards, BIOSes, and VGA cards on their websites.

CD-RW, floppy, and DVD-R drives can be added internally. Choose an approved FireWire OHCI PCI card and an ATA-66 PCI card or better needed to support additional ATA disk drives. We suggest that you use only Windows 2000 or XP and to go with applications and hardware supported by these operating systems.

Picking a PC laptop is not as easy as a desktop system. Some laptops have excellent FireWire ports but poor video display technology, which means they might capture video, but could drop frames on playback. It is best to purchase only models that have been approved by the publisher of the software you expect to use. Certain Sony VAIO laptop models are a good chioce and work well with Avid Xpress DV.

Choice of Computer Monitors:
Flat panel monitors are quickly dropping in price and improving in quality. They take less room, consume less power, and are much easier to move. We suggest you consider a 17 inch flat panel monitor as a minimum. However, a 19 inch CRT monitor will cost about one-third that of a 17 inch flat panel. A pair of 19 inch CRT monitors can be installed at less than the cost of single 17 inch flat panel and will be much more productive.

There are three different display connectors ­ analog VGA, and digital DVI and ADC, with ADC on Apple computers only. Most CRT monitors are VGA. Flat panel monitors come as VGA and/or DVI, and Apple's latest are ADC only (ADC is essentially DVI with additional connections for monitor power and USB). The latest (Mirror Front Panel) Power Macintosh computers ship with both a DVI and an ADC connector; the latest display cards lets you connect two monitors, one to the ADC port and one to the DVI or with an adaptor to a second ADC monitor, but the rest of the display cards are either/or, driving only a single monitor.

There are DVI to ADC converters that include power, and ADC to DVI adapters is also available. There are even adapters for using ADC monitors on PCs. Dual-display VGA host adapters for Macintosh and PCs are available so you can have two monitors without giving up a PCI slot for a second monitor card.

Storage and RAID Considerations:
Picking the storage that fits the type of editing you plan to do is very important, and making the right choice can save you hundreds of dollars. It is imperative that disk drives run within temperature specifications and be connected to quality cables and connectors for error free transfers. Use quality cables, quality connectors, and make sure air management is good enough to keep the hard disk drives cool. Drives that run at higher temperatures not only shorten their useful life but generate more errors. The internal chamber of a disk drive must maintain a given level of relative humidity in order for the heads to fly properly. If the drives get too hot, the relative humidity drops, making it more difficult for the heads to stay on track, resulting in retries. During these extra spins the drive's buffer is not being refilled with data, possibly resulting in dropped frames.

If the wrong types of cables or connectors are used they can be a source of errors and can lead to data corruption. The choice of cable technology is very important. For ATA drives, we suggest only 80 pin ATA-100 cables that include a ground line between each data line for optimum performance and few if any errors.

ATA vs. SCSI:
ATA drive technology continues to improve each year and has replaced SCSI in many applications due to their lower cost and improved performance. ATA technology is designed to be used with short cables inside the computer cabinet, while SCSI supports longer cables making it the choice for external storage and for high performance RAID systems.

ATA-133:
If you plan on editing using DV or DVCAM as your source, 7200 RPM ATA Ultra DMA drives offer plenty of bandwidth. There is no need to consider a RAID storage system. A single ATA-133 drive connected to an ATA-66 or ATA-100 port will sustain 35 MB/sec reads and high as 45 MB/sec writes. DV and DVCAM use only 3.6 MB/sec and will run clean with a minimum sustain rate of 7 MB/sec.

So you see, 35 to 45 MB/sec from current technology is more than enough for DV and DVCAM. However, single ATA disk drives do not produce high enough sustained rates for uncompressed SD video from a single drive. In the new mirror faced G4 computers that have 3 ATA ports one can add 4 additional ATA drives that can be stripped as RAID-0 that will produce sustained data rates high enough for uncompressed SD video. In this case it is best to move the boot drive to the lower optical drive and connect it to a PCI ATA card.

At ProMax we avoid 5400 RPM hard disk drives especially when used with long video projects, where disk fragmentation and complex areas on the timeline can be a source of dropped frames. Adding multiple audio tracks can also cause dropped frames since each audio track becomes a separate file, causing latency issues during head movement. (Audio creates latency issues, whereas video is more I/O intensive.) With one track of video plus four tracks of audio with cross fades, you have created nine separate files on the drives. Now add titles, transitions, and effects, all of which add more files, and you see that these parts of the timeline can become very complex and can result in dropped frames during playback.

We suggest 80 or 120, 180, or 200 GB ATA-133, 7200 RPM drives that are field proven. Hatachi/IBM drives have the best microcode for controlling the drive, and the best electronics allowing longer cables than other brands. Longer cables are often needed for installing multiple drives in a computer.

At ProMax we avoid certain brands of disk drives such as Maxtor due to their heavy failure rates and errors, as reported on video forums such as www.2-pop.com and DV-L. Note that not everybody has trouble with Maxtor drives. However, for most people their data is very important. We stay with tried and proven components as insurance.

If you are installing ATA storage in one of the newly released Power Macintosh Dual Processors G4's with DDR we have discovered that you can install 4 additional ATA drives and still keep the original boot drive - as well as a DVD-R (SuperDrive) or a CD-RW (Combo) drive. In this case the boot drive is mounted with side brackets in the lower optical bay and is connected to a special cable that is connected to the ATA-33 port on the motherboard and feeds the top bay optical drive as well. Four additional low profile hard disk drives can be added by placing two in the factory mounting bracket on the right and two in the factory mounting bracket under the optical drive enclosure. Data cables and power are provided by Apple for the four drives. There are three ATA ports on the new motherboards ­ ATA-33 for optical drive. The ATA-66 and ATA-100 are for use with disk drives. We find excellent performance from both the ATA-66 and ATA-100 ports. In fact with OS X you can stripe these four drives and get data rates high enough for Standard Definition with Realtime previews using the AJA Kona SD card. It is best to connect the boot drive to a PCI ATA-133 card to speed opening of applications, etc.

FireWire Storage Systems:
FireWire disk storage is becoming very popular, especially for those who do not have room internally for adding additional storage, as on a laptop or PowerBook computer. FireWire drives are also excellent for moving large amounts of video data between computer stations.

Like early SCSI storage, FireWire drives have had their issues. Second generation bridge chips have improved performance and compatibility. FireWire drives are nothing more than ATA drives converted to FireWire via a bridge. Early on these bridges were bottlenecks. With the new Oxford 911 bridge, transfer rates from 35 to 45 MB/sec is possible. These rates are more than enough for DV/DVCAM video editing.

One should be aware that picking a FireWire drive with an Oxford 911 bridge is only a part of the choice. Not all cabinets are created equal, nor are all bridges and device drivers. Cabinets with internal power supplies tend to work better than those with wall mounted power supplies.

Be aware of differences in FireWire cables. Well-shielded cables are imperative. They should be no longer than the IEEE spec of 4.5 meters. Don't plan on daisy chaining more than two or three on the same bus, and it works best if all the drives employ the same bridge technology. Mixing FireWire disk drives and deck/camcorders on the same bus can be tricky. If problems occur, changing the position of the devices in the FireWire chain or trying different lengths of cables can help.

FireWire 800 ports are now included on new Apple computers. Soon FireWire 800 disk drives will start to appear that employ the Oxford 922 bridge technology. FireWire 800 uses a 9 pin connector, which should be more reliable and cause fewer problems. FireWire 800 data rates should be as much as 20% higher than FireWire 400. Remember the limiting factor is the read/write channel of disk drives not the interface. In time drives will be faster as higher density drives come to market.

On to Part Two...

Copyright 2003 by ProMax Systems, Inc., Irvine, California.
Charles F. McConathy is the President and CEO of ProMax Systems, Inc. which is a leading provider of Turnkey solutions for NLE workstations.

Written by Charles F. McConathy.
Thrown together by Chris Hurd.