An Overview of Video Format Characteristics
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:
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. For more information, see Storage Medium. 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. For more information, see Tape Size, Cassette Shape, and Tape Coating. The video standard supported: For example, NTSC, PAL, ATSC (HDTV 1080i or 720p), and so on. For more information, see Video Standards. 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. For more information, see Types of Video Signals. The aspect ratio of the pixels: This is a subtle factor that is explained in more detail in Pixel Aspect Ratio. The frame rate: The number of frames recorded per second. For more information, see Frame Rate. The scanning method: Interlaced fields (two fields per frame) or progressive (one complete frame at a time). For more information, see Scanning Method. Color recording method: RGB, component (YUV), S-Video (Y/C), or composite. For more information, see Color Recording Method. 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). For more information, see Color Recording Method. 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. For more information, see Video Sample Rate and Bit Depth. 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. For more information, see Bit Depth. 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. For more information, see Video Compression.