Methods are disclosed for inserting local ad assets into a video transport stream at the set top box level. The media advertising platform of the present system works in conjunction with existing platforms, such as an advertising decision service and a media platform. The present system further includes a client resident on end user set top boxes. In general, the present system operates by pre-caching advertisements to a set top box or boxes within a household or elsewhere. Each set top box is also assigned to particular groups, based on characteristics of the user of that set top box. Group membership information is also sent to the set top box and stored. The present system sends the set top box a decision matrix based on group memberships to allow the set top box to select and insert an ad asset targeted to the specific set top box.