common in computer virtual reality applications such as in a Cave Automatic Virtual Environment, but reduces effective video framerate by a factor of two. Formats Different layers of video transmission and storage each provide their own set of formats to choose from. For transmission, there is a physical connector and signal protocol (see List of video connectors). 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 coding format, of which a number are available. Analog video Analog video is a video signal represented by one or more analog signals. Analog color video signals include luminance, brightness (Y) and chrominance (C). When combined into one channel, as is the case, among others with NTSC, PAL and SECAM it is called composite video. Analog video may be carried in separate channels, as in two channel S-Video (YC) and multi-channel component video formats. Analog video is used in both consumer and professional television production applications. Digital video Digital video signal formats have been adopted, including serial digital interface (SDI), Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI) and DisplayPort Interface. Transport medium Video can be transmitted or transported in a variety of ways including wireless terrestrial television as an analog or digital signal, coaxial cable in a closed-circuit system as an analog signal. Broadcast or studio cameras use a single or dual coaxial cable system using serial digital interface (SDI). See List of video connectors for information about physical connectors and related signal standards. Video may be transported over networks and other shared digital communications links using, for instance, MPEG transport stream, SMPTE 2022 and SMPTE 2110. Display standards Digital television Digital television broadcasts use the MPEG-2 and other video coding formats and include: ATSC – United States, Canada, Mexico, Korea Digital Video Broadcasting (DVB) – Europe ISDB – Japan ISDB-Tb – uses the MPEG-4 video coding format – Brazil, Argentina Digital Multimedia Broadcasting (DMB) – Korea Analog television Analog television broadcast standards include: Field-sequential color system (FCS) – US, Russia; obsolete