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Ross Video Vision 4
Ross Video Vision 4

A vision mixer (also called video switcher, video mixer or production switcher) is a device used to select between several different video sources and in some cases composite (mix) video sources together and add special effects. Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images This is similar to what a mixing console does for audio. In professional audio, a mixing console, or audio mixer, also called a sound board or soundboard, is an electronic device for combining

Contents

Explanation

Typically a vision mixer would be found in a professional television production environment such as a television studio, cable broadcast facility, commercial production facility, remote truck/OB Van or linear video editing bay. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic A television studio is an installation in which Television or Video productions take place either for Live television, for recording Live to tape A television advertisement or television commercial (often just commercial or advert (US or ad (UK is a span of television programming produced Linear video editing is the process of selecting arranging and modifying the images and sound recorded on Videotape whether captured by a Video camera, generated The term can also refer to the person operating the device.

Vision mixer and video mixer are almost exclusively European terms to describe both the equipment and operators. In the United States, the common name for a device of this kind is (video) production switcher and the common name for the operator of the device is known as technical director. The United States of America —commonly referred to as the The Technical Director ( TD) or Technical Producer ( TP) is usually the most senior technical person within a Software Company, Theatrical

Software vision mixers are also available. A software vision mixer provides similar functionality to that of a hardware Vision mixer.

Capabilities and usage in TV Productions

Besides hard cuts (switching directly between two input signals), mixers can also generate a variety of transitions, from simple dissolves to pattern wipes. A switch is a mechanical device used to connect and disconnect an electric Circuit at will In Film editing, a wipe is a gradual spatial transition from one image to another Additionally, most vision mixers can perform keying operations and generate color signals (called mattes in this context). Compositing is the combining of visual elements from separate sources into single images often to create the illusion that all those elements are parts of the same scene For the technique of creating backgrounds see Matte painting. Most vision mixers are targeted at the professional market, with newer analog models having component video connections and digital ones using SDI. This article is about analog component video for the processing of color components in digital video see Digital video, Chroma subsampling and YCbCr Serial digital interface (SDI refers to a family of Video interfaces standardized by SMPTE. They are used in live and video taped television productions and for linear video editing, even though the use of vision mixers in video editing has been largely supplanted by computer based non-linear editing. "Live TV" redirects here For the British TV station formerly known by this name see L!VE TV. Videotape is a means of recording images and sound onto Magnetic tape as opposed to movie film. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Linear video editing is the process of selecting arranging and modifying the images and sound recorded on Videotape whether captured by a Video camera, generated A computer is a Machine that manipulates data according to a list of instructions. Video editing software is Application software which handles the editing of video sequences on a computer

Older professional mixers worked with composite video inputs. Composite video is the format of an Analog television (picture only signal before it is combined with a sound signal and modulated onto an RF There are still a number of consumer video switchers with composite video, S-Video or even FireWire available. Super Video or Separated Video abbreviated S-Video and also known as Y/C is an analog video signal that carries the video data as two separate The IEEE 1394 interface is a serial bus Interface standard for high-speed communications and Isochronous real-time data transfer frequently These are often used for VJing, presentations, and small multi-camera productions.

Operation

The main concept of a professional vision mixer is the bus, basically a row of buttons with each button representing a video source. Pressing such a button will set the video out of that bus. Older video mixers had two equivalent buses (called the A and B bus, such a mixer is known as an A/B mixer). One of these buses could be selected as the main out (or program) bus. Most modern mixers, however, have one bus that is always the program bus, the second main bus being the preview bus. These mixers are called flip-flop mixers, since the selected source of the preview and program buses can be exchanged. Both preview and program bus usually have their own video monitor. A video monitor also called a broadcast monitor, is a device similar to a Television, used to monitor the output of a video-generating device such as a media

Another main feature of a vision mixer is the transition lever, also called a T-bar or Fader Bar. This lever, similar to an audio fader, creates a transition between two buses. Note that in a flip-flop mixer, the position of the main transition lever does not indicate which bus is active, since the program bus is always the active or hot bus. Instead of moving the lever by hand, a button (commonly labeled "mix" "auto" or "auto trans") can be used, which performs the transition over a user-defined period of time. Another button, usually labeled "cut" or "take", directly swaps the buses without any transition. The type of transition used can be selected in the transition section. Common transitions include dissolves (similar to an audio crossfade) and pattern wipes. Crossfade is a Post-grunge / Hard rock band from Columbia South Carolina.

The third bus on a vision mixer is the key bus. A mixer can actually have more than one of these, but they usually share only one set of buttons. Here, a signal can be selected for keying into the program. The image that will be seen in the program is called the fill, while the mask used to create the keys' translucence is called the source. This source, e. g. chrominance, luminance, pattern (the internal pattern generator is used) or split (an additional video signal similar to an alpha channel is used) and can be selected in the keying section of the mixer. Chrominance ( chroma for short is the signal used in many Video systems to carry the color information of the picture separately from the accompanying luma As applied to video signals luma represents the brightness in an image (the "black and white" or achromatic portion of the image In Computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial transparency Note that instead of the key bus, other video sources can be selected for the fill signal, but the key bus is usually the most convenient method for selecting a key fill. Usually, a key is turned on and off the same way a transition is. For this, the transition section can be switched from program (or background) mode to key mode.

These three main buses together form the basic mixer section called Program/Preset or P/P. Bigger production mixers may have a number of additional sections of this type, which are called Mix/Effects (M/E for short) and numbered. Any M/E section can be selected as a source in the P/P stage, making the mixer operations much more versatile, since effects or keys can be composed "offline" in an M/E and then go "live" at the push of one button.

After the P/P section, there is another keying stage called the downstream keyer. It is mostly used for keying text or graphics, and has its own "Cut" and "Mix" buttons. The signal before the downstream keyer is called clean feed. In television technology clean feed is a term that describes the output of a Vision mixer before the downstream keyer stage After the downstream keyer is one last stage that overrides any signal with black, usually called FTB or Fade To Black.

Modern vision mixers may also have additional functions, such as machine control, aux channels for routing signals to other sources than the program out, macro programming and DVE (Digital Video Effects) capabilities. A macro (from the Greek 'μάκρο' for long or far in Computer science is a rule or Pattern that specifies how a certain input sequence (often a sequence

Setup

Since vision mixers combine various video signals such as VTRs and video cameras, it is very important that all these sources are properly synchronized. VTR redirects here For other meanings see VTR (disambiguation. A video camera is a Camera used for electronic Motion picture acquisition initially developed by the Television industry but now common in other applications In professional facilities a sync generator feeds all the equipment. Sync can also be achieved by sending out a black burst signal from the switcher (this method is called "genlock" ). Signals which cannot be synchronized (either because they originate outside the facility or because the particular equipment doesn’t accept external sync) must go through a frame store synchronizer. Some vision mixers have internal “frame-syncs” or they can be a separate piece of equipment, such as a "time base corrector". If the mixer is used for video editing, the editing console (which usually controls the vision mixer remotely) must also be synched. Most larger vision mixers divide the control panel from the actual circuitry because of noise, temperature and cable length considerations. The control panel is located in the production control room, while the main unit, to which all cables are connected, is located in a machine room alongside the other hardware. A television studio is an installation in which Television or Video productions take place either for Live television, for recording Live to tape

Some Manufacturers of vision mixers

References

See also

A patch panel or patch bay or jackfield is a panel typically Rackmounted that houses Cable connections Used for transporting Audio signals from inputs to outputs Inputs and Outputs The number of inputs and outputs varies dramatically Video Routers are used for transporting Video signals from inputs to outputs
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