Content transmission system and method

A content encoding system for generating content to be output to a client device, the system comprising a content obtaining unit operable to obtain video content for display at the client device, an asset determining unit operable to determine one or more assets to be associated with the display of the video content at the client device, an asset package identifying unit operable to identify one or more asset packages comprising respective ones of the determined assets, and determining one or more asset package identifiers associated with those packages, and an encoding unit operable to generate an encoded stream comprising the video content and the one or more asset package identifiers.