• Synchronization method should be compatible with various kinds of TVs and mobile devices (including
devices even not connected with a network).
• Playback time of the main content on TV, called TV time, must not be delayed.
• Main and sub content on a mobile device screen should be synchronized within one frame (about 0.03 seconds or less).
The requirements of the authoring environment are defmed below.
• It should be an integrated environment to produce both main and sub content.
• Universal formats for component files should be available.
• 3DCG character's basic motions, such as walking or sitting down, can be designated easily, for example, by
action commands.
• Interactive content can be produced.