What Does "Decoding" Mean in Regard to an Audience Viewing

What does "decoding" mean in regard to an audience viewing media content?

A) It refers to the process of figuring out how much money and time went into creating the content.
B) It is the thought process of what it would be like to be "behind the scenes" of the content.
C) It is a form of hacking that the viewer follows in a science-fiction film.
D) It is the process of using implicit knowledge of both medium-specific and broader cultural codes to interpret the meaning of a media text.