Sony Vision Mixer

[Elijah Rakestraw]

Therole of the vision mixer for video is similar to what a mixing console does for audio. Typically a vision mixer would be found in a video production environment such as a production control room of a television studio, production truck or post-production facility.

Besides hard cuts (switching directly between two input signals), mixers can also generate a variety of transitions, from simple dissolves to pattern wipes. Additionally, most vision mixers can perform keying operations (called mattes in this context) and generate color signals. Vision mixers may include digital video effects (DVE) and still store functionality. Most vision mixers are targeted at the professional market, with newer analog models having component video connections and digital ones using serial digital interface (SDI) or SMPTE 2110. They are used in live television, such as outside broadcasting, with video tape recording (VTR) and video servers for linear video editing, even though the use of vision mixers in video editing has been largely supplanted by computer-based non-linear editing systems.[1]

Older professional mixers worked with composite video, analog signal inputs. There were a number of consumer video switchers with composite video or S-Video. These are often used for VJing, presentations, and small multi-camera productions.

The most basic part of a vision mixer is a bus, which is a signal path consisting of multiple video inputs that feeds a single output. On the panel, a bus is represented by a row of buttons; pressing one of those buttons selects the video signal in 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), and 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 (sometimes called preset) bus. These mixers are called flip-flop mixers, since the selected source of the preview and program buses can be exchanged. Some switchers allow the operator to switch between these two modes. Both the preview and program bus usually have their own video monitors displaying the video selected in their respective buses.

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, is used to 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, swaps the preview signal to the program signal instantaneously. The type of transition used can be selected in the transition section. Common transitions include dissolves (similar to an audio cross fade) and pattern wipes.

A third bus used for compositing is the key bus. A mixer can have more than one key bus, but often they share only one set of buttons. Here, one signal can be selected for keying over the program (or background) bus. The digital on-screen graphic image that will be seen in the program is called the fill, while the mask used to cut the key's 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. 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 mode to key mode. Often, the transition section allows background video and one or more keyers to be transitioned separately or in any combination with one push of the auto button.

Modern vision mixers may also have additional functions, such as serial communicationswith the ability to use proprietary communications protocols, control auxiliary channels for routing video signals to other sources than the program out, macro programming, and DVE capabilities. Mixers are often equipped with effects memory registers, which can store a snapshot of any part of a complex mixer configuration and then recall the setup with one button press.

Since vision mixers combine various video signals such as VTRs and professional video cameras, it is very important that all these sources are in proper synchronization with one another. In professional analog facilities all the equipment is genlocked with black and burst or tri-level sync from a video-signal generator. The 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 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 hardware that performs the mixer functions because of noise, temperature and cable length considerations. With such mixers, the control panel is located in the production control room, while the main unit, to which all cables are connected, is often located in a machine room alongside the other hardware.

The main purpose of a vision mixer is to create a master output for a real-time video recording or broadcast. Typically vision mixers are used for live events, or any event where multiple sources need to be mixed in real-time (as opposed to post-production editing).

The vision switcher takes their instruction from the director. Basically, the director decides what is going to happen and tells the switcher to do it. A typical set of instructions might go like this:

EMG Germany located near Cologne specialises in studio, field and post production for broadcast delivery. It works mainly in formats that suit entertainment and educational material, but also operates an OB vehicle delivering productions for major sports events such as European or World Championships.

The system is upgradable to UHD or IP at any time, if required, supporting the SMPTE ST 2110 suite of open standards for media over managed IP networks. This means users can run a mixed IP and SDI production environment. 100G IP boards support 4K and HD in a single stream, with on-board format conversion available.

"We have been using Sony vision mixers for a long time," said Christian Boden, who is New Technology Manager at EMG Germany and responsible for the replacement. "We've had very good experience throughout the system changeover, from helping us develop the best concept for our purposes and evaluating the system size, to giving technical advice."

As well as modules familiar to the user, the XVS-6000 utilises Sony ICP-X7000 X-Panels, which also have a modular design for very flexible panel configuration. The new XPT pads ease operation of the panels and allow direct access to system resources. Numerous transition modules are available, plus track ball, key fader and shot box modules.

Ren Steinbusch, CEO of EMG Germany, said, "A major advantage when switching from the MVS to the XVS live video mixer series is familiarity and logical operating philosophy. In our hectic daily production routine, this is enormously important and it made this system change relatively easy for us. In addition, there is very good support from the Sony people, efficient communication channels and a training offer."

"The experience of our customers flows into the development work and is used to continuously improve Sony products in terms of a consistent operating and ergonomic concept," said Christian Hesse, Key Account Manager Germany at Sony Europe. "We also have a strict focus on designing live video mixers like the XVS-6000 to meet upcoming requirements regarding UHD and remote production, for example, or IP expansions." pro.sony

The Blackmagic Design Atem Television Studio Pro 4K is an all-in-one desktop unit capable of switching, video effects, color grading, keying and audio mixing. It boasts eight 12G-SDI inputs supporting camera and computer signals ranging from HD to full UHD. The Atem Television Studio Pro 4K also features an AUX output to send a clean or program feed to an additional destination.

The Broadcast Pix BPswitch is a unique switching solution with a focus on a control-over-IP approach that allows operators to control it from anywhere, using either a tablet, phone or panel solution. By utilizing cloud-based control video directors are able to take advantage of built-in features such as computer graphics, video clip storage, control of robotic cameras, live streamers and recording.

The Datavideo KMU-100 offers an interesting alternative for small and mid-sized churches looking to take their production quality to the next level. The switcher allows video directors to frame up to four different HD shots from a single 4K camera signal, then create a live switch from these four shots. By adding a second 4K camera the KMU-100 can implement an additional four shots, providing users the option to live switch up to eight different angles.

The Grass Valley GV Korona Production Switcher is a professional broadcast solution designed specifically with houses of worship in mind. It features an extensive control surface with a built-in OLED touchscreen for full control of the system. The power and functionality of the GV Korona can be greatly enhanced when paired with the K-Frame V-Series Processing Engine, allowing for an all IP or mixed SDI and IP signal environment.

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