Information storage medium storing graphic data and apparatus and method of processing the graphic data

A method of processing graphic data, the method comprising:

• decoding graphic object data defining a plurality of graphic objects, each of the plurality of graphic objects being identified by an object identifier and to be displayed with video data as a subtitle or a menu;
• storing, in a first buffer, the decoded graphic object data for a predetermined time, such that the plurality of graphic objects remain available for use for the predetermined time;
• decoding composition information;
• storing, in a composition buffer, the decoded composition information;
• generating graphic data to be output to a display device by composing the plurality of graphic objects using the decoded composition information stored in the composition buffer, the generated graphic data comprising at least some of the plurality of graphic objects which have the object identifiers referred by the decoded composition information stored in the composition buffer;
• storing, in a second buffer, the generated graphic data;
• and
• outputting the graphic data stored in the second buffer to the display device.