Video is an electronic medium for the recording, copying, playback, broadcasting and display of moving visual media.Video was first developed for mechanical television systems, which were quickly replaced by cathode ray tube (CRT) systems which were later replaced by flat panel displays of several types.
Video download systems vary in display resolution, aspect ratio, refresh rate, color capabilities and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcast, magnetic tape, optical discs, computer files, and network streaming.
Video clip download can be interlaced or progressive. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. Interlacing was invented as a way to reduce flicker in early mechanical and CRT video download displays without increasing the number of complete frames per second. Interlacing retains detail while requiring lower bandwidth compared to progressive scanning.
Video download quality can be measured with formal metrics like Peak signal-to-noise ratio (PSNR) or through subjective video download quality assessment using expert observation. Many subjective video clip download quality methods are described in the ITU-T recommendation BT.500. One of the standardized method is the Double Stimulus Impairment Scale (DSIS). In DSIS, each expert views an unimpaired reference video download followed by an impaired version of the same video. The expert then rates the impaired video download using a scale ranging from “impairments are imperceptible” to “impairments are very annoying”.
Different layers of video clip download transmission and storage each provide their own set of formats to choose from.
For transmission, there is a physical connector and signal protocol (“video connection standard” below). A given physical link can carry certain “display standards” that specify a particular refresh rate, display resolution, and color space.
Many analog and digital recording formats are in use, and digital video clips can also be stored on a computer file system as files, which have their own formats. In addition to the physical format used by the data storage device or transmission medium, the stream of ones and zeros that is sent must be in a particular digital video download compression format, of which a number are available.
From late 2005 to early 2006, a new form of blogging emerged called a vlog. It is a blog that takes video as the primary content, often accompanied by supporting text, image, and additional metadata to provide context. Su Li Walker, an analyst with the Yankee Group, said that like blogs, which have become an extension of traditional media, video blogs will be a supplement to traditional broadcasting. Regular entries are typically presented in reverse chronological order and often combine embedded video or a video link with supporting text, images, and metadata.
Corporations have used Web video download in communicating with people and in driving traffic to their sites. According to one article, the most common types of corporate Web video are:
Video success stories
Video Case Studies
Man-On-the-Street interviews and market research
Product presentations and video brochures
Presentations, Trade Shows and Events
Training and support videos
Commercials and Infomercials