videoReferee®-8F – Basic VAR system for football
The accessible, quick and compact videoReferee®-8F system is a junior model in the line of our Video Assistant Referee (VAR) systems for football. It meets all the FIFA requirements and technical standards which allows it to be used in competitions of any level. The compact (2U, 12 kg) system is suitable for mobile solutions.
videoReferee®-8F based VAR solution can record up to 8 3G*/HD SDI camera signals in various installation options:
- local installation in the VOR at the stadium,
- mobile solutions (VAR Van),
- VAR center.
The videoReferee® system has a User Native Interface that significantly speeds up the work of the VAR team in making important decisions, imperative during the game.
Interface monitors
Notable features include the ability to work with interface monitors (up to 4* monitors), which can display:
- Engineer Interface.
- VAR Interface, which works in the following modes:
- Live recording,
- Delayed video with adjustable delay up to 3 seconds from 1/2/3 or 4 cameras,
- Standard search interface for review,
- Playback of the selected camera with adjustable speed.
- Multiviewer that displays all video input channels. Multiviewer allows to select the required camera and perform simultaneous search on all channels for quick moment location and review.
- One backup monitor. Can be used for Main camera output.
The special MultiSkin function allows to display several interfaces on one monitor with the ability to switch between them. For example, Engineering or VAR interfaces can be displayed on one monitor by pressing a button on the referee control panel to switch between them.
Full-fledged gesture interface for VAR monitor
All videoReferee® systems have built-in support for the gesture interface on the VAR monitor. In addition to the standard function of zooming the image in/out, the gesture interface allows camera selection, search, video playback control and playback speed control. These functions are used with simple and intuitive gestures.
Unlike Touchscreen, the gesture interface is much faster, does not require looking for controls and accurately hitting them, and keeps attention of the VAR focused.
Referee buttons
Complying with FIFA requirements, the system can include special referee buttons. In the standard configuration the buttons are used for controlling communication between VAR and the referee on the pitch, marking of events and timing control.
Safety of recording
The specifically designed file subsystem and I-Frame DCT Based codec ensure the safety of video material and its rapid recovery during the server boot after a power supply loss.
Redundant power supply option further reduces the likelihood of such issues.
Specialized referee control panel Control-VR
The specialized referee control panel significantly speeds up the workflow. It provides the VAR or replay operator instant access to all cameras, presets and most other functions.
The last generation of the Control-VR is equipped with 35 RGB backlit buttons and a proprietary Jog/Shuttle for positioning and controlling playback of recorded video. The control panel is connected via RS-232 / RS-485 / USB or Ethernet.
Remote operation
A special VAR.IO device added to the system can provide long-distance control using the local Ethernet network. This allows for placement of the control panel, buttons, keyboard, and mouse at a convenient place away from the server. The device also lets you set up control of several servers from one place.
Permanent licenses
videoReferee® VAR systems come with permanent software licenses that do not require regular renewal.
Integration with intercom systems
The videoReferee®8F system has a communication interface with referee intercoms and referee communication recording capabilities in accordance with FIFA requirements. The system has a hardware option to interface with the Vokkero intercom with volume control and an intercom option for VOR.
Complying with the requirements for VAR technology, the microphone of the VAR team is activated by pressing a dedicated button to avoid inadvertently feeding the VOR conversations into the referee intercom. Conversations between the VAR (or AVAR) and the head referee on the pitch are recorded in the server.
Loop play
The Loop play is provided with an adjustable 1 or 2 seconds duration, as well as with using input and output marks. Loop play is managed via Control-VR panel and works for one or several channels in Quadrator mode.
RRA option
The system's RRA option provides an output signal of a duplicated VAR interface with the review in progress to the RRA monitor. In the absence of a VAR interface it displays a background picture. Additionally, it generates graphics with the referee's decisions for the Venue Information Graphics systems. It is controlled from the Control-VR panel.
Duplication of VAR interface on the RRA monitor and outputting infographics to the arena and the broadcast
The SLOMO.TV VAR servers can provide the Venue Information Graphics thanks to the RRA-II option – an external device with 6 SDI outputs, any of which can be assigned one of the following functions in any combination:
- VAR interface output without additional graphics
For supervisor workstation, control monitor, shared video wall in VAR center, etc.
- Synchronous duplication of the VAR interface to RRA zone in accordance with FIFA
requirements
In the absence of a VAR interface the RRA monitor displays a static image to ensure privacy.
- VAR server information graphics output to the arena or broadcasting
Pre-loaded infographics about the actions of the VAR team or the final decision are output from the server to the arena and the broadcaster by a member of the VAR team.
The flexibility of the RRA-II configurations greatly simplifies VAR installation and can be used in place of a separate subsystem with an operator.
Advanced export capabilities
The video content can be exported in a variety of file formats, including MXF XDCAM HD422 50 Mbps. Both marked events and the entire recording from all cameras can be exported. The ability to mark the start and end of the exported segment allows you to create files with the necessary moments.
There is also export to special file formats, compatible with the Academy system. That allows using real game situations with the review of real moments for training.
Offside solutions
ThevideoReferee®VAR is integrated with Deltacast's virtual offside line – 2D/3D VOL. The SLOMO.TV VAR and Delta-offside systems exchange VOL images via a local 1GbE network.
For quick resolution of controversial moments the Control-VR panel is equipped with a “VOL” button to transfer all necessary data to the Delta-offside system, as well as to display the processed image to the referees.
VAR / AVAR / RO workplaces
The standard configuration allows organizing of workplaces for VAR, AVAR, and RO in compliance with FIFA recommendations.
SSM camera support
videoReferee®-8F has optional support for Super Slow Motion cameras from most manufacturers. The number of SDI inputs required to connect an SSM camera corresponds to its shooting speed.
Examples of camera configuration for 8 channels:
- Five HD cameras + one 3x SSM camera
- Four HD cameras + two 2x SSM cameras
Academy – intensive training technology
Specialized training technology for referees, assistant referees and cameramen based on the Academy server.
The Academy system simulates live synchronized video signals from cameras or OB Van and allows VARs to train in conditions as close to reality as possible.
The system helps to learn and practice the order of actions for various controversial moments.
The Academy uses a library of training clips with controversial moments. The user can expand this library with previously unreported moments or create his own for continuous professional development of VAR teams or training of new ones.
This system significantly reduces the training time of new operators, and provides advanced training by parsing a library of real controversial moments.
videoReferee®-8F system in details
- 8 3G*/HD recording channels
- 1 workplace for VAR/assistant VAR/Replay Operator
- Quick preparation of a controversial moment for review. Loop play mode
- Virtual Offside Line technology integration
- Referee intercom integration
- VAR interface output to RRA and broadcasting. Venue Information Graphics
- Support for Super Slow Motion cameras*
- Up to 3 seconds (75 frames) adjustable delay displaying of the Main Camera on VAR monitor
- Controversial moment review at normal and slow motion speed
- ZOOM and Frame-by-Frame viewing which provides 50/60 individual phases of movement when working with a standard signal
- Intuitive gesture interface with camera selection, playback speed control, ZOOM and Frame-by-Frame viewing
- Control-VR panel – instant access to the necessary cameras, presets, convenient search and markup
- Quick creation of camera and multi-screen presets
- RGB referee buttons – VAR and chief referee intercom (conversation is recorded), start of control stopwatch, marking of events
* – optional
| Parameters | videoReferee®-8F |
|---|---|
| Inputs 3G*/HD SDI | 8 |
| Video formats | Support for modes 16:9 и 4:3 |
| HD SDI | 29.97/59.94 Hz: 1920x1080/59.94i, 1920x1080/29.97PsF, 1280x720/59.94p, 720x480/59.94i 25/50 Hz: 1920x1080/50i, 1920x1080/25PsF, 1280x720/50p |
| 3G SDI* | 1920x1080/59.94p, 1920x1080/119.88i, 1920x1080/50p, 1920x1080/100i |
| Channels (simultaneously) | |
| Recording | 8 |
| Search or Playout | 1 / 2 / 3 / 4 or 1 |
| Video Standards SDI | |
| HD/SDI | HD video conforms to SMPTE 292M, SMPTE 274 720p video conforms to SMPTE 296M |
| 3G SDI* | 3G video conforms to SMPTE 424M /SMPTE 425M |
| Interface monitor | 2 (DP, HDMI™) / 4 * |
| Referee output for broadcast | HD SDI*Option RRA monitor |
| Multiviewer | Up to 10 video windows. 2 Layouts Option Delay Mode 3s |
| Gesture control | |
| (Touch screen monitor is provided by user. Recommended: Iiyama multi-touch monitor) | Embedded touch screen control |
| Referee workplaces | 1 |
| Compression: | |
| Recording | I-Frame DCT Based |
| Export formats | M2TS; MPEG-4 (*.mp4); H264 (*.mp4); DVD; XDCAM 50 (*.mxf) (for HD only) |
| Internal storage | SSD |
| Storage capacity | |
| HD SDI | Up to 84 hrs. Full HD video 100 Mbit/s |
| 3G SDI* | Up to 40 hrs. Full HD video 200 Mbit/s |
| Audio Inputs | 2 embedded audio channels per video channel (embedders are not included) |
| mini-vR-Cam Audio Inputs | 2 audio sources per camera |
| Audio Outputs | MB audio output / HDMI™ |
| Scoreboard Interface** | External*/ PiP from any camera |
| Controls | Specialized Jog/Shuttle controllers Control-VR (via RS-232 /RS-485 / USB / Ethernet), keyboard, mouse |
| Referee buttons | Up to 4pcs.:
Green (mark events); Red (intercom control); Blue (timer control). Via USB connection. |
| Virtual offside lines | Yes (Delta-offside) |
| Referee intercom integration | Native Vokkero support with adjustable audio level control |
| Additionally | Ability to network with SLOMO.TV servers |
| Data exchange | 10 GbE (Network); USB 3.0; Built-in trayless/toolless 3.5" SATA HDD Rack |
| Built-in DMR™ RACK | 1 |
| Maximum distance of connections | SDI up to 110m; 3G SDI up to 90m; Control up to 150m; DP / HDMI™ up to 5m |
| Power Consumption | 120 W |
| Power | 110V/60Hz or 220V/50Hz |
| Redundant PWR Supply | Yes* |
| Chassis | 2U, 19″ |
| Dimensions (H x W x L) mm | 88 х 482 х 512 |
| Weight Kg | 12 |
|
Notes: * – optional. ** – Supported: Westerstrand, Nautronic NTpult, Nautronic NAUCON-1000, Bodet, Omega Saturn, Megalux, NataInfo, Victory, VITA, Araneus–NGLight, ElTablo, Stramatel, Colosseo, CEDR, Favero Console-700. |
|
| Option | Description | Type |
|---|---|---|
| Integration with Referee intercom | Communication between VAR and referee on the field is activated by pressing a button, conversations are recorded by the server | Hardware |
| VOL | Seamless integration with 2D / 3D virtual offside line system (Delta-offside, Deltacast VOL) | Software |
| RRA option with infographics for spectators | SDI video output of the VAR interface to the RRA (FIFA compliant) and to broadcasters. videoReferee®-8F also allows to output standard infographics with the VAR team's actions and the final refereeing decision from the VAR server to the arena and to broadcasters | Hardware |
| SSM camera support | Support for 2x, 3x, 4x SSM cameras. (Requires 2-4 dedicated input channels). |
Software |
| 4 monitors option | 2 additional monitors support | Hardware |
| Redundant power supply option | Dual mini redundant Power Supply. | Hardware |
| Second workstation option | Includes a second Control-VR console and 2 additional monitors support | Hardware |
| SLA support | Agreement | |
| System operation training for VARs | Training |
VOL (Virtual Offside Line)
VOL (Virtual Offside Line) is a system designed to accurately assist football referees in offside situations. As an integral part of the VAR (Video Assistant Referee) ecosystem, VOL system by SLOMO.TV combines advanced 3D calibration techniques, video synchronization, and human expertise to help make well informed decisions.
Basic principles
Unlike older 2D systems that were used to project lines onto the pitch plane, VOL technology is designed to solve a three-dimensional problem. It determines the position of key body points of the involved football players (legs, torso) at the moment of the pass in real 3D space.
Key stages of offside detection:
- Locking the moment of the pass: Specialized cameras determine the exact moment when the ball is touched by a player from the passing team.
- 3D-scene construction: The VOL system analyses the position of all players relative to the goal line, using data from synchronized cameras and considering the actual pitch topography (irregularities of the field).
- Position analysis: The position of the attacking player is compared with the position of the second to last defending player.
Difficulties of the VOL system operation process
To accurately detect offside in football, numerous factors related to the geometry and topology of the football pitch must be considered. In this article, we will examine the main challenges faced by Virtual Offside Line (VOL) systems.
The perfect football pitch
An ideal football pitch should comply with FIFA recommendations regarding dimensions, markings, and surface parameters, and should be perfectly flat.
However, deviations are allowed, which may affect the performance of the VOL system.
Deviations in line markings
Some football teams may adjust their line markings at the home pitch. Minor changes in line markings become a tactical tool for the home team and may affect the correct rendering of offside lines by the VOL system.
In our practice, we have also encountered situations where pitch markings were asymmetrical relative to the half-way line. This may lead to errors when drawing the offside lines. In reality the deviations may be 10–20 cm in either direction – a significant difference for offside decisions.
Moreover, we've met cases where the main pitch marking rectangle (touch lines and goal lines) forms a rhombus or trapezoid instead of a rectangle. With a pitch length of 100 m, the error may amount to about 0.1%. However, when the VOL system is expected to detect offside with 1 cm accuracy, this error becomes significant and affects decision making.
Topological features of the football pitch
A football pitch is a complex structure and is not always perfectly flat. The pitch’s drainage system ensures water flows towards the edges to prevent stagnation, resulting in bulges in the center and slopes at the edges.
For the VOL system to operate correctly, three-dimensional pitch parameters must be considered. Any irregularities complicate the drawing of a straight line due to potential distortions, which may affect the final offside detection.
VOL system and cameras
When the VOL system uses cameras positioned close to the pitch edge, errors may occur due to incorrect height determination in the model. For instance, if a camera is mounted 10 m from the pitch edge at human height, and players are at the opposite end of the pitch (up to 50 m away), the offside line drawing error may reach 50–100 cm if the VOL system does not account for local height differences.
It is also necessary to consider image distortion when drawing offside lines. Shooting with cameras of different focal lengths leads to distortions where straight lines appear curved. In the VOL system, wide angle shots require offside lines to be drawn curved accounting for this distortion.
Improving VOL system performance
When working with a regular, non-ideal football pitch, we face numerous complexities that must be considered. To correctly draw the offside line, pitch and line marking measurements are required, along with constructing a topological model of the entire pitch, including all three-dimensional irregularities. Additionally, it’s worth considering to use cameras that reduce the likelihood of VOL system errors.
Creating a model of the pitch
Let's consider a regular football pitch with known topological coordinates for standard points (31–35 points) which are uploaded to the VOL system. If a disputed incident occurs near standard points within 1 m, the VOL system operates with high accuracy.
However, an incident may also occur at a considerable distance from known points. Given that depressions and bulges are distributed across the pitch, a more accurate three-dimensional topological pitch model must be created to ensure acceptable VOL system accuracy. This requires a grid with a larger number of points.
In our opinion, an acceptable grid for normal VOL system operation has a cell size of 2×2 m. The optimal grid has 1×1 m cells. This is a substantial pitch measurement task, but it enables accurate line drawing.
Of course, performing topology scans before each match is costly and impractical. For each pitch where matches may be held, a topological map must be created – a 3D object onto which the current actual pitch dimensions and line markings can be overlaid. This allows offside lines to be drawn as accurately as possible on a three-dimensional surface, as relative coordinates and necessary measurement heights will be known.
📄 Our guide to collecting field topology data for VOL technology
Optimizing cameras for offside detection
Another challenge is the need to capture potential offside incidents with a camera providing sufficient detail for the VOL system. When using broadcasting cameras, it may turn out that no suitable camera was available for offside detection in a specific situation.
This is addressed by installing fixed cameras that are always capable of capturing complex incidents. For example, the Premier League uses 30 cameras for precise fixed offside detection. They allow accurate determination of player positions in three-dimensional space.
Installing a large number of cameras requires substantial stadium equipment investment but guarantees high accuracy in offside detection and resolution of disputed incidents.
Our recommendations
For maximum efficiency within reasonable budgets, the following steps can be taken to improve VOL system accuracy:
- Perform topological pitch measurements twice: at the start of the season and in the mid-season. Also, perform pitch topology scans whenever pitch parameters change – e.g., when line markings are significantly altered or the turf is replaced. (📄 Instructions for collecting field data for using VOL technology).
- Whenever possible, conduct topological scanning of main pitch points (31–35 points) during line marking. Estimated task duration: 2 hours.
- Use special 16 m cameras positioned on each side of the pitch to capture the maximum number of disputed incidents.
- Ensure fixed cameras are synchronized with broadcasting cameras; otherwise, errors may reach up to 10 cm when capturing at 50i/50p.
- It is not enough to rely only on high-speed cameras (100-120 frames per second). Using four dedicated offside cameras and one overview camera can significantly reduce coordinate detection errors.
Main advantages of our VOL system
Our solution has the following technological and operational advantages:
🔗 Full integration with our VAR system
VOL is a software option running on the same hardware as our VAR system, not a separate server. This means:
- No need for additional hardware or control units
- Control is performed via the native VAR console (or mouse)
- It saves a lot of resources: takes no extra space, needs no extra purchases, and one operator can handle all functions
🎮 User controlled
The VOL operator has full control. Using an augmented reality tool (with a 3D crosshair) they can place markers on protruding body parts of players. This tool is displayed simultaneously on all selected cameras, allowing accurate positioning from different angles. This eliminates errors of relying on abstract player models
🌍 Consideration of the pitch topology
A football pitch is not a perfectly flat plane. The system requires mandatory pre-match calibration to create an accurate 3D model of the pitch, accounting for all depressions and mounds. This takes less than a minute per camera and ensures decisions are based on the stadium’s real geometry
⚡ Absolute camera synchronization
SLOMO.TV technology synchronizes all video streams with 0.5 frame accuracy, even for the initially unsynchronized cameras. This is imperative for reliably aligning the moment of the pass with the relative positions of the players
⏱️ High speed
Thanks to an intuitive interface and augmented reality technology, the operator spends up to 30 seconds on a standard incident and up to 60 seconds in complex cases, maintaining game pace
⚙️ Technical information
📐 Infrastructure recommendations
- Fixed cameras: We recommend using stationary offside cameras installed at 16 m from the goal line, perpendicular to the touch line. Four such cameras (two on each side) reliably capture up to 95% of incidents. Installing eight cameras is ideal
- SuperMotion cameras: To improve accuracy, using 100-120 fps cameras is recommended (for example, the mini-2x-vR-Cam). Standard 50 fps cameras have a margin of error of 4–20 cm. SuperMotion cameras halve this error, making it possible to evaluate disputed moments when the differences measure in centimeters
🧩 Hybrid VAR architecture
When using a VAR Center configuration as a VAR solution (a central hub equipped with the VAR system and VAR workstations), increasing the number of cameras requires expanding communication channels.
SLOMO.TV offers a hybrid approach, where the VAR server is installed at the arena directly, while the VAR workstations and the VAR team are located in a remote VAR Center. This way, adding 4, 8, or 16 cameras does not change the signal transmission requirements, as everything is handled locally.
🔌 Connectivity
SuperMotion cameras (such as mini-2x-vR-Cam) connect via a standard Ethernet network with PoE power supply. The cloud synchronization technology allows the system to be scaled to meet any requirement without loss of quality
VOL by SLOMO.TV is a fast, accurate, and reliable solution. Integrated into all VAR servers starting in 2026, it is available to all users of our systems as part of standard technical maintenance.
videoReferee®-8F basic configuration
- 2U server videoReferee®-8F with support for 8 3G*/HD/SD recording channels
- 2/4* graphic outputs (MultiSkin function for displaying different interfaces on a
single monitor with ability to switch between them):
-
Referee interface operating in the following modes:
- Delayed video from the main camera or delayed Multiscreen of 2, 3 or 4 cameras
- Step-by-step search through multiple camera recordings
- Playback of a selected camera with adjustable speed
- Engineering interface
- Multiviewer
- Main camera
-
Referee interface operating in the following modes:
- Gesture control support (VAR monitor)
- 4 RGB back-lit ergonomic referee buttons
- VAR/assistant VAR/replay operator workstations (monitors to be purchased by the user)
- Specialized Control-VR panel
- Standard keyboard
- Mouse
* – optional
