There is a systematic approach followed while making films and in that, the promotion starts once the shooting is completed. In that process, the heroes and heroines come up with different bytes for different media entities. However, all that is becoming a thing of the past.
A new development is that the promotional bytes are being taken from the hero and heroine right during the film shooting. This is because, some of them are not available during promotion time because they are busy with next films and sometimes they do not show that much of interest.
So, during shoot itself, the promotion bytes are also taken so that time is saved, budget is saved and no new call sheets are required. This is not just from the lead cast but also from the key technicians associated with the project. This is indeed a smart move from the makers.