Playback apparatus, program, and playback method

A program for causing a computer to perform processing of playing back a graphics stream and a video stream, wherein

• the graphics stream includes one or more interactive control segments and one or more graphics data pieces,
• each interactive control segment includes a plurality of sets of page information and time-out information,
• each set of page information includes one or more button information pieces,
• each button information piece realizes an interactive screen structure by displaying each graphics data piece as a state of a corresponding graphics button, material,
• the time-out information indicates a time on a playback time axis of the video stream at which the interactive screen structure is ended,
• the computer comprises:
• a plane memory storing therein graphics to be played back;
• a page number register storing therein a page number of a current page;
• and
• a button number register storing therein a button number of a current button, which is one of the button materials in a selected state on the current page,
• the program causes the computer to execute a decoding step of (i) obtaining a page including a plurality of graphics button materials by decoding the graphics stream, and (ii) writing the obtained page to the plane memory,
• when a selection of one of the button materials on the current p age is confirmed, the program further causes the computer to execute a set command, which sets a new button umber in the button number register, in the decoding step,
• the button number stored in the button number register is cleared when a current playback time has reached the time indicated by the time-out information, and
• the clearing of the button number is performed by the decoding unit deleting the written page from the plane memory.

A method used on a computer for playing back a graphics stream and a video stream, wherein

• the graphics stream includes one or more interactive control segments and one or more graphics data pieces, each interactive control segment includes a plurality of sets of page information and time-out information,
• each set of page information includes one or more button information pieces,
• each button information piece realizes an interactive screen structure by displaying each graphics data piece as a state of a corresponding graphics button material,
• the time-cut information indicates a time on a playback time axis of the video stream at which the interactive screen structure is ended,
• the computer comprises:
• a plane memory storing therein graphics to be played back;
• a page number register storing therein a page number of a current page;
• and
• a button number register storing therein a button number of a current button, which is one of the button materials in a selected state on the current page,
• the method comprises a decoding step of, on the computer, (i) obtaining a page including a plurality of graphics button materials by decoding the graphics stream and (ii) writing the obtained page to the plane memory,
• when a selection of one of the button materials on the current page is confirmed, a set command is further executed in the decoding step, the set command setting a new button number in the button number register,
• the button number stored in the button number register is cleared when a current playback time has reached the time indicated by the time-out information, and
• the clearing of the button number is performed by the decoding unit deleting the written page from the plane memory.