Apple Final Cut Pro 6 - Manual (Page 1859)

376 Part V Appendixes
 Color sampling: For component digital formats, the ratio of color samples to
black-and-white (or luma) samples (for example, 4:4:4, 4:2:2, and 4:1:1).
 Sample rate: The number of samples per second of each video line. This is just like
the sample rate for audio, except the signals sampled are video lines, where each
sample represents light intensity instead of sound intensity.
 Bit depth: The number of bits used to store each video sample, which determines the
ability of the format to capture each sample’s (or pixel’s) light intensity precisely, and
how well subtle differences in intensity can be stored.
 Compressor (or codec): A video compressor attempts to reduce the amount of digital
data required to store each frame without compromising the quality of the image.
Storage Medium
Video—especially digital video—can be stored on more than just videotape. The
characteristics of the storage medium determine playback and recording capabilities.
For example, magnetic and optical disc media (such as CDs, DVDs, and hard disks) are
capable of nonlinear reading and writing, whereas videotape is inherently linear.
Videotape is still a very efficient means of storing large amounts of digital data in a
small space, but other types of media are quickly gaining ground.
Tape Size, Cassette Shape, and Tape Coating
The width of a videotape is directly related to how much information can be stored. In
analog formats, wider tape usually yields higher quality, but other factors can help
reduce tape size with minimal loss of quality. For example, Betacam SP and VHS both
use 1/2"-wide tape, but Betacam SP uses a high-quality component video recording
method that keeps luma and chroma information separate, whereas VHS uses a
composite method that mixes these signals into one, causing interference between the
two. The physical formulations of these two kinds of tape are also different, which
accounts for some of the quality difference.
The size of the cassette itself can vary as well. For example, the Betacam SP format
comes in both small and large sizes. The small tapes are used for camcorders, while the
large format is used in studio VTRs.
Aspects of the physical composition of magnetic tape, such as density of magnetic
particles, limit the data rate and track size that can be recorded on the tape. The
magnetic coating on a videotape is formulated to work with particular camcorders and
VTRs. If you choose the wrong tape coating, the tape can actually clog the video record
heads of your video equipment, leading to video signal dropouts during recording and
playback. Always read the documentation that comes with your video equipment
before purchasing a particular brand of videotape stock.