There is provided mechanisms for identifying decreasing object detectability for a video stream. A method is performed by a controller. The method includes receiving the video stream over a communication channel. The method includes receiving first visual object detection (VOD) data of the video stream. The first VOD data has been obtained from the video stream before is sent over the communication channel towards the controller. The method includes obtaining second VOD data of the video stream. The second VOD data is obtained from the video stream after is received by the controller. The method includes determining, by comparing the first VOD data to the second VOD data, whether any object present in the first VOD data has a decreased object detectability in the second VOD data, thereby identifying the decreasing object detectability for the video stream. The method includes issuing a notification when the decreasing object detectability has been identified.