It will depend on where the TV display is located! It is not the same answer for a display located inside an elevator as for another placed in a waiting room. In an elevator where users are available for 10 seconds while moving from one floor to another, it won’t l be functional to have videos of 15 seconds or more. The spectator does not expect to finish the announcement to lower the elevator so the communication will be interrupted.
On these displays or on the television sets in the waiting rooms, there is more time for the viewer to stay and, therefore, there is a greater opportunity to inform. A display located in the waiting room of a medical clinic could use ads for 30 seconds or more, since it is the only dynamic means of entertainment at that time. In particular, you can find a utility for the audience such as news for a certain period of time.
The next question to ask: How many seconds will the consumer watch on the display? We should take into account that the client will hardly observe only the display while visiting the premises, therefore the announcement can not be extensive. This includes the purpose of the client observing the complete publication, without spending a lot of time, that is, simply take a look and get the ad.
On average, a functional ad should last somewhere between 10 and 15 seconds. However, it always depends on the time spent and location of the TV display you are using