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# Object Tracker
## Overview
The Object Tracker plugin is a model plugin that propagates bounding boxes forward through video frames.
Use this plugin when you have manually marked an object in one frame and want the plugin to create predicted bounding boxes for the following frames.
## Plugin Functionality
The Object Tracker plugin runs on video assets. It looks for bounding-box annotations whose class title ends in `_toTrack`, tracks those boxes forward through the video, and returns predicted bounding boxes using the matching class without `_toTrack`.
For example, if your ontology contains:
* `Vehicle`
* `Vehicle_toTrack`
you can draw a `Vehicle_toTrack` bounding box on a video frame. The plugin will create predicted `Vehicle` boxes on later frames.
{% hint style="warning" %}
The plugin only processes bounding-box annotations with class titles ending in `_toTrack`. Make sure the project ontology also contains the matching destination bounding-box class without `_toTrack`.
{% endhint %}
### Supported Data Types
* Video
### Supported Annotation Tools
* Bounding Box
## Plugin Configuration
You may vary a number of settings related to tracking from the **Config JSON** field. Each option is detailed below:
```json
{
"model_index": 4,
"num_predictions": 20,
"stride": 1,
"include_key_frames_only": true
}
```
* **"model\_index":** Selects the OpenCV tracker used by the plugin.
* Options:
* 0: BOOSTING
* 1: MIL
* 2: KCF
* 3: TLD
* 4: MEDIANFLOW
* 5: MOSSE
* 6: CSRT
* Example:
* "model\_index": 4
* **"num\_predictions":** Maximum number of future frames for which the plugin should attempt to create predictions.
* Example:
* "num\_predictions": 20
* **"stride":** Controls how often predicted boxes are returned. A stride of 1 returns every predicted frame, while a higher value skips intermediate predictions.
* Example:
* "stride": 1
* **"include\_key\_frames\_only":** Included in the default configuration for consistency with video plugins. Object Tracker follows the frames it processes from the source video.
* Example:
* "include\_key\_frames\_only": true
---
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