Concepts

Models

Signality API hinges on three different levels, represented as models.

Venues

A venue corresponds to a specific sport location (arena, stadium, etc.).

In addition to name, address and location, a venue can include permanent video streams information (RTSP URIs to IP cameras).

Games

As the name suggests, a game is a full activity event at a specific venue.

In addition to the venue identifier, a game includes an activity type (for example, soccer), a start time and home and away teams information (name, lineup and possibly formation).

Phases

A phase is the basic unit of play of the activity.

In soccer, for example, a game is typically composed of two phases (half times) of 45+ minutes.

A phase includes start and end times, the kickoff team, substitutions and red cards.

Camera Setup

This section describes optimal 2 camera and 4 camera settings to ensure optimal tracking.

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Figure 1. One possible camera setup and desired field of view.

Figure 2. 4 camera setup and desired field of view.

Image Quality

To avoid issues related to image quality, the following precautions should be taken:

  • 3840x2160 (4K) resolution.
  • Codec H264 with maximum bitrate 8192 kbps.
  • Widely accepted video format, e.g. (seekable) HLS stream.
  • Appropriate color balance, similar in both pitch halves.
  • Appropriate focus settings to reduce blur.
  • Shutter speed at least 60 Hz.
  • Frame rate at least 25 FPS.
  • No WDR or HDR settings in camera.

Camera Positioning

Positioning of the 2 cameras in the long side

To avoid tracking issues, the cameras should be positioned as follows:

  • At least 80 degrees field of view.
  • At least 10 meters above and 4 meters from side lines.
  • Maximum 0.25 meter distance between cameras, ideally the right hand camera covers the left hand side of the pitch and vice versa. Stationary mounting surface - vibrations impairs tracking.
  • Behind the player benches.

Positioning of the cameras behind the goals

  • Distance to the goals: At least 4 meters behind the goals.
  • Height: At least 10 meters.
  • Angle with the pitch: Between 20 and 40 degrees
  • Framing: The nearest goal, both corners, and the center circle should be visible.
  • Orientation: The goal line should be horizontal.

For all cameras:

  • The cameras should be positioned so that they are not exposed to direct sunlight. Very bright sunlight can result in lens flares, exposure issues and suboptimal white balance. This can be avoided with a sun shield and ensuring a clean lens.
  • The camera positioning should be chosen so that potential occlusions are avoided. This can be from a variety of things: smoke, flags, sun blinds, bleachers, poles, ropes ors cables. Stationary or moving objects occluding the pitch will impair the tracking.

Example Images

Figure 3. Example of accepted camera angle.

Figure 4. Example of too low camera angle.

Figure 5. Example of good positioning of camera behind the goal

Landmarks

Soccer

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