Some DVD Definitions
DV, MiniDV, DIGITAL 8 ... HELP!
By Dirk Fischer, Educational Technology Consultant
Just when you've figured out the difference between VHS, S-VHS and VHS-C along comes digital video and a whole new slew of acronyms. Below are some helpful definitions, but first I'd like to explain something.
Many people think that digital video is uncompressed that the picture information stored on the tape is untouched, unprocessed. But even professional broadcast digital video camcorders use compression. The difference between the uncompressed size and the compressed size is called the "compression ratio," usually printed "5:1" or whatever it may be. The "5:1" formula means "five to one" and indicates that the video has been compressed to one-fifth of its uncompressed size.
Now, the definitions:
DV: This is a consumer digital-video format that uses quarter-inch-wide tape in a cassette and has a 5:1 compression ratio. It has a "track width" of 10 microns (millionths of a meter) for each line of magnetic information recorded. DV tape speed is 16.9 millimeters per second.
MiniDV: MiniDV is the name of a small videocassette. Do not mistake it for a recording format. You can use MiniDV cassettes in DV, DVCAM and DVCPRO (but not in DIGITAL 8) devices. Because it's used most often in DV camcorders, the DV format is often referred to as MiniDV, but technically it is still DV just in a tiny cassette housing.
DIGITAL 8: Sony's DIGITAL 8 uses DV compression atop the existing Hi8 (8 mm wide tape) technological base. DIGITAL 8 can record on regular Hi8 tapes (cheaper than digital tapes), but these run at twice their normal speed and thus hold half the time listed on the label.
Check out this site for more information: http://www.adamwilt.com/DV.html. For more than you ever wanted to know about videotape, go to http://lionlmb.org/quad/theory.html.
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