Analog Video is usually captured by a video camera and then digitised. There are a variety of video (analog and digital) formats (Chapter 6)
Raw video can be regarded as being a series of single images. There are typically 25, 30 or 50 frames per second. Therefore a 512x512 size monochrome video images take 25*0.25 = 6.25Mb for a minute to store uncompressed. Digital video clearly needs to be compressed.