How is a "video signal" defined?

A video signal is defined as baseband including visual information, which accurately reflects the essence of what a video signal is. Baseband signals refer to the original form of a signal that has not been modulated for transmission. In the case of video, this means that the signal carries visual information without undergoing modulation to a higher frequency. This is crucial because the clarity and fidelity of the images displayed depend on the integrity of the baseband signal. The video component consists of the necessary visual information that allows images to be rendered on screens.

The other options either do not capture the specific definition of a video signal or apply to different contexts. For instance, a composite signal typically combines audio and video into a single signal, which may not always convey just the video component. An analog signal that carries no information does not define a video signal, as video signals must carry distinct visual data, whether in analog or digital formats. On the other hand, while digital signals can represent video information, the inclusion of "compressed data" in the definition does not always apply, as video signals can also be uncompressed. Therefore, the choice that clearly defines a video signal as baseband including visual information is the most accurate.