Characteristics of Video Formats
All video formats achieve the same basic goal: they store black-and-white or color
information as electronic lines that make up a video frame. The number of video frames
recorded per second varies depending on the video standard the format supports (for
example, NTSC formats are recorded at 29.97 fps; PAL formats are recorded at 25 fps).
Video formats can be characterized by the following factors:
Â The medium used to store the video information: This is primarily videotape, but can
also be optical disc, solid-state memory, or a hard disk.
Â The size of the media and the shape of the shell: For example, videotape may be 1", 1/
2", 3/4", or 8 mm. Many video formats have different shell sizes for portable and
studio use, such as mini-DV (portable) and the larger DV cassettes for studio decks.
Â The video standard supported: For example, NTSC, PAL, ATSC (HDTV 1080i or 720p),
and so on.
Â The type of electronic signal recorded on tape: In other words, the way luma
(black-and-white) and chroma (color) information are combined and recorded.
Â The aspect ratio of the video frame: The ratio of the frame width to the frame height.
Â The dimensions of the video frame: The number of pixels per line, and the number of
lines per frame.
Â The aspect ratio of the pixels: This is a subtle factor that is explained in more detail below.
Â The frame rate: The number of frames recorded per second.
Â The scanning method: Interlaced fields (two fields per frame) or progressive (one
complete frame at a time).
Â Color recording method: RGB, component (YUV), S-Video (Y/C), or composite.
Â 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).
Â 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.
Â 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.
Â 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.