A continuously high bitrate in a video stream, even when using H.265 compression, is often due to significant movement within the scene. High levels of motion require more data to be encoded to maintain image quality, resulting in a higher bitrate. This is because the video encoder must frequently update large portions of the image to accurately represent the moving objects. Axis Communications' documentation on video bitrate management indicates that scenes with much movement lead to increased bitrate due to the dynamic changes requiring constant encoding.