Tech Talk

Tech Talk

On page 39 of the September '96 issue of Videomaker, you said that Windows 95 uses 16-bit video components, but imply that it is also 32-bit in other ways. I'm confused by this statement. Could you enlighten me, please?

John B. Cason

The designers of Windows 95 had a tough task: to make a 32-bit operating system that would run all existing 16-bit DOS 6.22 applications. Since all 32-bit systems exchange data in 32-bit chunks, this presented a problem.

Their solution was to create a system that switches nimbly between 16-bit and 32-bit operations. Thus, when you load a 16-bit device driver in your Windows 95 config.sys file, the system automatically operates that device in 16-bit mode.

This is why it's possible to say, as David Brott did in the September issue, that Windows 95 is a 32-bit operating system that still relies on 16-bit components. If every piece of hardware in your computer (graphics card, CD-ROM, video capture card, hard drive controller, etc.) had a 32-bit driver, then Windows 95 would become a true 32-bit operating system. Most systems, however, still rely on 16-bit drivers for at least a portion of their hardware.

Windows NT solves this problem with brutal elegance by simply refusing to operate any hardware with a 16-bit driver. This was one of the reasons for the development of Windows 95: to create a bridge between 16-bit and 32-bit versions of Windows, a bridge built of 32-bit device drivers and applications.

What is a control track? What does it do? Where is it recorded? Who put it there? When do we use it? Why don't 8mm and Hi8 have one? I'm very confused. Can you put me on the right track?

Tharanga Ramanayake
Toronto, Canada

The term "control track" (sometimes abbreviated CTL) describes the linear strip of information that's recorded alongside the diagonal video tracks on a videotape. The purpose of the control track is to store synchronization information (the "sync signal") so that playback equipment--monitors, etc.--will be able to decode the video signal correctly.

VHS and S-VHS tapes make use of linear control tracks; 8mm and Hi8 tapes, however, use frequency modulation to store the sync signal along with the video and AFM audio signals in the same diagonal tracks. This is why 8mm and Hi8 recordings don't require a separate control track; the same information is there, but it's recorded differently.

I was shopping for an A/V optimized hard drive the other day when someone suggested that I use a RAID system to store my digital video files. What's a RAID system, and how does it work?

Chet Orland
Honolulu, Hawaii

A RAID (Redundant Array of Independent Disks) is a grouping of several standard hard disks with a hardware RAID controller. When you use hard disks in this configuration, the whole becomes more powerful than the sum of its parts; in addition to higher capacity, RAIDs offer faster data transfer rates and increased data security than single-drive systems.
The most common form of RAID used in high-end digital video is a level-3 RAID. In this system, all but one of the hard disks writes incoming digital information in 512-byte sectors, while the additional hard disk writes a 512-byte parity sector for data verification. The RAID then groups these sectors into a single super-sector, which becomes the minimum unit of data transfer into or out of the system. In this way, the RAID allows several disks to operate at the same time, increasing the data throughput considerably.

Recently, I bought a Panasonic Broadcast and Television Systems AG456 camcorder, but I'm running out of storage space for these S-VHS tapes. I'm considering the purchase of a VHS-C cassette adapter so I can use the more compact S-VHS-C tapes instead of the full-size version.
Would the use of this VHS-C system work well in my AG456? Can it harm my camcorder in any way?

Lynden Brown
Nassau, Bahamas

Stop! Before you put that ordinary VHS-C adapter in your precious S-VHS camcorder, you should know that these two pieces of equipment were not designed to work with one another. Whenever you put anything into that delicate tape transport system that wasn't intended to be there, you risk permanent damage to the heads, pins, rollers, eject mechanism, etc. of your camcorder.

A story came to us once of an individual who attempted to do what you're describing with his S-VHS editing deck. When he tried to insert an S-VHS-C cassette, the adapter became inextricably stuck in the tape transport, and the whole mess had to be shipped off to the manufacturer for repairs.

For your storage problems, you might consider purchasing longer-playing S-VHS tapes. Even though many professionals prefer shorter running times for greater reliability, high-quality 120- minute S-VHS tapes work well for most situations. This is more than twice the capacity of the longest S- VHS-C tape now available on the market.


Sun, 12/01/1996 - 12:00am