Video is an analog electronic medium for the playback, recording, copying, encoding, and displaying of moving visual information. Video has been around since at least the late nineteen hundreds. The very early systems used magnetic tape recorders and video recorders. Video is now almost as ubiquitous as electricity, with the exception of telecommunications. Video was initially developed for industrial television systems, which soon were replaced by cathode ray Tube systems that were later replaced on to flat screen monitors of various kinds.
Digital systems have greatly improved over the years, as well as the development of high-speed Internet and video-conferencing. As a result, nearly every type of consumer display and communications equipment now uses some form of digital signal, whether for general purpose (i.e. computer video and audio data) or specific purposes (i.e. digital telephone video).
NTSC (National Television System Certification) is a common acronym for National Television System Code. It was originally developed for use in digital television sets, but has been generalized to include other types of consumer display equipment such as home video systems. This code is used to identify the characteristics of a video display including the vertical lines, horizontal lines, scan lines, aspect ratio, and response time. A common misconception is that it refers to the quality of the video, but the term actually refers to the quality of the video signals themselves – the response time and the artifacts caused by interaction between the signal source and the video display.
Refresh rate and response time are important characteristics of a video display system because they determine how fast a signal can be transmitted over a long distance. They also affect the quality of video images. There are basically three kinds of refresh rates: true-oscillation, half refresh, and progressive scan. Progressive scan displays the video with a smooth progression from one frame to the next while true-oscillation involves the video being displayed in rapid successive steps.
The most widely used format for both DVD and VCR is the analog video format, which is also the oldest type of television broadcast. Analog video uses a magnetic tape system to record the video signal and convert it to the required analog signal. This signal is then sent to a receiver, and is again converted into the desired picture-quality image using a demodulation process. The disadvantage of analog video is the limitations in the range of channels, signal filtering, and recording speeds.
The latest format for DVD and VHS use a progressive scan mode. In a progressive scan mode, the video signal is captured on an x-ray disc and is then electronically scanned by the monitor. When this process is complete, the desired picture is then produced on the TV. While this technology provides higher quality images than the previous method, it also has more moving parts and requires more electricity. For this reason, modern TVs are now fitted with advanced home video devices that support the Progressive scan mode. Advanced DVD and HDTV sets now offer both the convenience and improved picture quality of progressive scan video.