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Image comparison identifies which parts of an image have changed, by comparing the image to a reference image that is stored in the Media Server database. You can run image comparison on a video file or stream - in this case Media Server compares each video frame to the reference image.
You can use image comparison to identify changes in a scene. You might want to identify new objects that have appeared, objects that have disappeared, or objects that have moved to different locations.
If you have deployed Media Server for security and surveillance purposes, you can capture an image of the scene from a camera and store this in the database. Then, you can compare subsequent images to the reference image and identify any changes, such a person being present in a restricted area. Having an automated process to identify changes like this can significantly reduce the amount of data that needs to be reviewed by a human operator.
The images that you send to Media Server for comparison should be similar to your reference images in terms of perspective and rotation. The images do not need to be the same size but if there are significant changes in perspective or rotation Media Server will consider the entire image to have changed.