More DV NLE Gotchas

The hard disk you choose to handle media is a major issue. An UltraDMA/ATA-100 drive with 7200 RPM or more, like this Seagate Barracuda,offers excellent performance.

As I discussed in last month's column, buying a DV format editingsystem involves considering many options before you decide on a system.There are many “gotchas” that can come between you and yourDV NLE. To avoid these, I have listed some of the issues you shouldconsider when purchasing a DV-format NLE.

Last month, I covered software and hardware choices, and how tochoose a VCR to work with your system. This column will focus onconnectivity issues, storage options, and miscellaneous other gotchasthat can make life with your DV NLE difficult.

Connectivity is a concern that you should ponder carefully whenbuying a DV-format NLE. While FireWire (aka IEEE 1394 or i.LINK) is themost common connection, there are alternatives and reasons forconsidering an alternative method. For example, you will not be able todo frame-accurate insert editing through FireWire. Audio issues,including the ability to input alternate audio-only sources, audiosynchronization delays, and the ability to mix audio tracks prior toentering them into the NLE system are also problems associated withinputting media through FireWire. Depending upon system configurationand source, there may be issues of timecode accuracy, and sourcetransport controls may not function properly.

Apple and Panasonic have already announced that they are working ona next-generation FireWire 800 (IEEE 1394b) connection that will handle800Mbps video streams and feature other improvements. While we willhave to wait for the specifics, 24p/variable frame rate and connectionsto less compressed formats will be the primary benefits. Most softwaremanufacturers will eventually develop drivers for the new,faster-throughput connection.

Another FireWire gotcha is using an incompatible IEEE 1394 interfacecard. Generally, an Open Host Controller Interface (OHCI) should beused to connect devices. This is an industry standard endorsed byMicrosoft, Apple, Hewlett Packard, Intel, Sun Microsystems, NationalSemiconductor, and Texas Instruments, among others. The standard isdesigned to ensure that software drivers and applications arecompatible with OHCI-compliant hardware.

Alternative connectivity options include RS-422 transport controlwith SDTI or SDI inputs/outputs, and USB or USB 2.0 connectivity. TheRS-422 transport control is the industry-standard VCR control interfaceand has been for decades. It is almost always frame accurate andbulletproof. The SDI connection is the granddaddy standard for digitalvideo — especially for connecting uncompressed video betweendevices.

The newer SDTI standard, an industry compromise between thecompressed digital video interface proposals put forth by Sony (QSDI)and Panasonic (CSDI), offers metadata container standards and a way ofingesting media at four times normal speed with VCRs offering thiscapability.

The USB port is being used for DV import by a number ofWindows-based computers. The USB 2.0 standard is competing withFireWire for dominance as the “digital pipe” of choice forhigh-bandwidth throughput needs. The technologies and capabilities arecomparable.

The hard disk you select for your media is also a major concernsince this is another potential bottleneck. The disk must be fastenough to handle the performance you require, and most softwaremanufacturers recommend keeping your media on a separate hard disk.Frequently they will qualify specific hard disks and drivecontrollers.

As a general rule when working with a DV-based nonlinear editingsystem, this hard disk can be a second ATA drive. An Ultra DMA/ATA-100(7200 RPM or greater) with the proper hard disk controller card willoffer excellent performance.

An external IEEE 1394 or USB 2.0 drive is another popularalternative storage solution. This does not require a space for thehard disk within the computer nor does it add heat to the platform'sinterior. These external drives are actually ATA hard disks with aconnection bridge and external housing. Those with internal powersupplies appear to last longer and work better.

Also, look for an Oxford 911 bridge chip specification or the newOxford 922 bridge chip. This technology was designed to work withFireWire nonlinear editing platforms. If using this method of storage,use properly shielded high-quality cables and connectors.

Associated with FireWire and USB connections is the problem ofganging multiple devices and having the system not be able to handlethe configuration. Sometimes changes in OS system settings and BIOSneed to be addressed for a configuration to work. The most commonproblem is attaching a camera and an external drive and then using bothsimultaneously. Some editors with qualified cameras and external driveshave no problem, and others give up after trying to make theirconfigurations work. You should only use devices specified by thesystem manufacturer. If problems still occur, try changing the positionof the devices in the FireWire chain or try shorter cable lengths.

A Small Computer System Interface (SCSI) storage solution costsapproximately twice as much as ATA storage, but benefits include fargreater performance and generally a much better warranty. SCSI harddisks are frequently the disks of choice for RAID storage systems, butmanufacturers such as Medéa have begun to offer storage systemsutilizing the less expensive ATA drives in a RAID configuration andwith a SCSI connection interface. Other manufacturers that offerlower-cost RAID drives include Rorke Data, Huge Systems, MicroNet, andPromicro Systems.

An excellent resource for additional information on storageconfigurations and other configuration issues is a white paper writtenby ProMax president Charles McConathy, “Configuration ofNon-Linear Digital Video Editing Systems.” It is available at www.promax.com/PDF/NLESystems.pdf.

Another storage option is one that allows you to record direct tohard disk in the field, and then use that disk as your media storagewith your editing system. Fast Forward Video, Focus Enhancements,Granite Digital, Laird Telemedia, SmartDisk, and Sony are among themanufacturers that offer such solutions.

The last storage solution I want to mention is a Storage AreaNetwork (SAN). These networks are especially common at post facilitiesand educational institutions, although even a personal project studiomight have shared storage with a graphics computer or a digital audioworkstation. These systems offer shared storage and software for mediaasset management, including management of shared metadata. With theadvent of Gigabit Ethernet as a low-cost alternative to Fibre Channelnetworks, SAN solutions are becoming more popular.

External drives are a popular storage solution. This external USBdrive from Western Digital comes in 40GB, 80GB, and 120GB sizes.

However, having a SAN does not guarantee that multiple users will beable to access the same footage at the same time without ill effects.SAN manufacturers include Rorke Data, Studio Network Solutions, JMRElectronics, DataDirect Networks, Hewlett Packard, Dell, NetworkAppliances, and Huge Systems.

Another storage concern is archiving your media. Removable hard disksolutions and optical media are two of the more popular alternativestoday. The continual plummeting of the cost of hard disks makesremoving them and storing them practical — at least short-termthrough lengthy client processes, or even long-term by charging theclients for the hard disks the way you might charge for videotape.Optical storage is becoming another nearline solution, especially withoptical disk servers from Asaca/Shibasoku or PowerFile. A simpler,lower-cost solution might be a DVD burner that can serve the dualpurposes of archiving and creating media for distribution.

Monitoring is a major gotcha with many DV-based editing systems.There are color space differences between IEEE 1394 I/O and NTSC I/O,but how do you monitor them? Unless you have a realtime video outputthat can go to external waveform monitor and vector-scope, you mustrender any questionable video segments and then play the renderedsegment out to WFM/VS monitoring for analysis.

Does your audio synchronize with the video when playing the timelineor ingesting? Is the monitoring an accurate representation of theaudio/video stream? This is frequently a function of configuration andsetup parameters, but the process of confirming these parameters can beconfusing.

Locked versus unlocked DV audio is another potential gotcha. Lockedaudio is the preferred method, but due to the cost of a locked audioclock, the format standard provides for the less expensive“unlocked audio” alternative. The total amount of syncslippage allowed in unlocked audio is +/- 1/3 frame, but this canresult in pops at edit points and other difficulties. (Note: Thisvariation does not cause audio to drift out of sync because thevariation is not cumulative in one direction; the video and audioclocks are still linked.)

To complicate audio matters further, DV records at three differentsampling rates: 32KHz, 44.1KHz, and 48KHz. (44.1KHz is always unlocked,but the other two sampling rates can be locked or unlocked.) This canresult in incompatibilities in output formats, incompatibility betweenaudio clips in the time-line, incompatibilities between work-groupworkstations, and other woes. The fix is care in production and properdeck and NLE setup in the post process.

Another concern is generational loss. Many will say, “But thisis digital!” It is true that digital clones are identical, butevery video process requires an uncompress/recompress process. When theselected codec uncompresses the video, it has to guess what the missingbits in the uncompressed video looked like. If you go through thiscycle too often, the errors are cumulative and degradation can becomenoticeable.

Choosing software with the best codec algorithm can make adifference. Fortunately, codecs are constantly improving, but youshould be aware of the “state of the art” at the time youbuy.

Some other gotchas are not post-oriented. Timecode breaks/restartson DV tapes are one example. Cameramen sometimes black their cameraoriginal tapes (recording silence, black, and timecode) before goingout in the field to shoot. Many camcorders will see and reset to thattimecode. If batch input is necessary, sometimes the only solution isto do a digital dub of the camera originals, laying in new continuoustimecode.

The safest ways to prevent DV gotchas are to educate yourself aboutpotential pitfalls, make wise investments, and create proper workflowsadapted to these new technologies.

Bob Turner has edited video on nearly every piece of equipmentever made. He can be reached at bobturner@attbi.com.

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