music that are enhanced by stereophonic sound are therefore the focus point of many modern trailers. Trailers preceding feature films are generally presented in the same format as the feature, being either 35 mm film or a digital format. High bandwidth internet connections allow for trailers to be distributed online at any resolution. Since the advent of Digital 3D, it has become common for a 3‑D feature film to be preceded by one or more trailers that are also presented in 3‑D. Collections National Screen Service contracts required that trailers be returned (at the cinema's expense) or destroyed; however, it required no proof of destruction, and depositing them in a waste bin counted. A market for trailers evolved as it became clear that some had a commercial value to collectors. Many of the trailers for films like the Star Wars series reported as 'destroyed' were taken back out of the bin and sold by cinema staff. As they cost about $60 each to make (1981 estimate) and were hired to the cinema for $10, such losses led to NSS increasing its rental charges, which led to a decrease in the number of trailers rented and shown to audiences. Some cinemas also began to show "trailer trash" programs of trailers without a main feature. Similarly, several DVDs containing nothing but trailers for films, typically from exploitation film genres, have been produced for sale. Other types of trailers Beginning in the late 1990s to early 2000s, and along with the development of the Internet and sites such as YouTube as well as animation techniques, more types of trailers began to be created due to easier and cheaper costs to produce and show trailers. Video game trailers In the late 1990s to early 2000s, more video game trailers have been produced as they become more mainstream to entice viewers to purchase the game. There are two main types of video game trailers: cinematic and gameplay. Cinematic trailers are usually made entirely separate from the game engine and rely more on CGI. Even though cinematic trailers do not represent actual gameplay and are a divisive promotional tool in the gaming community, they are commonly accepted as part of the advertising necessary to get a game to sell. Gameplay trailers, sometimes referred to as "in-engine" trailers, are made using the game engine and take place inside the game's actual environment. In theory, this implies that