# Image Comparison

Image comparison identifies which parts of an image have changed, when compared to an original image that is stored in the Media Server training database.

Before using image comparison, you must train Media Server by adding training images to the training database. For instructions that describe how to train Media Server, refer to the Media Server Administration Guide.

Configuration Parameter | Description
--- | ---
Database | The image comparison database to use to identify changes to an image.
Identifier | A comma-separated list of identifiers that specifies the reference images to compare the ingested image to.
Input | The image track to process.
MaxInputQueueLength | Can be used to place a limit on latency.
Metadata | A metadata field name and value that specifies the reference images to compare the ingested image to.
Region | A region of the image to restrict analysis to.
RegionUnit | (Deprecated) The units that the Region parameter uses to specify the size and position of a region.
RestrictToInputRegion | (Deprecated) Specifies whether to analyze a region of the input image or video frame that is specified in the input record, instead of the entire image.
SampleInterval | The interval at which frames are selected to be analyzed.
SyncDatabase | Specifies whether to synchronize with the training database before beginning the analysis task.
Type | The analysis engine to use. Set this parameter to `ImageComparison`.

## Output Tracks

Output track | Type | Description | Output1This column indicates whether the information contained in the track is included by default in the output created by an output task (when you don't set the Input parameter for the output task).
--- | --- | --- | ---
`Result` | `ImageComparisonResult` | Contains a single record for each reference image that Media Server compared the image to. | Yes
`ResultWithSource` | `ImageComparisonResultAndImage` | Contains the same information as the `Result` track, but each record also includes the analyzed image. | No

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