If you are tasked with reviewing hours of video files from surveillance cameras, keep in mind that most systems should have tools which will help you expedite the review.
1. As with a PDF of a document, the video should contain thumbnails which let you quickly scan the range of the video across multiple moments in time to see when there is relevant footage.
2. Some systems use motion histograms that will indicate where movement appears in a video image. These are similar to sound wave charts. The graphs are displayed above a timeline for the video, and will rise at the time ranges where motion is detected.
3. A system may allow you to designate a motion detection window in a specific area of the video, to detect when the pixels change in that window.
These windows can also be used to exclude areas of motion that you want a search to ignore.