Patent Document ID: 20110116763
Application ID: 12746844
Patent Status: 0

Claim One:
1. A playback device for playing back a subtitle stream in synchronization with a video stream, the playback device comprising: a video decoder operable to decode the video stream; a subtitle decoder operable to decode the subtitle stream to obtain a bitmap of a subtitle; and a color conversion unit operable to convert bit values of the bitmap into display colors based on a color lookup table, the display colors including a character color, a background color, and one or more gradation colors for gradation therebetween, and the color lookup table including pieces of color information corresponding one-to-one to indexes of the bit values, wherein prior to the conversion, the subtitle decoder detects a period on a time axis of the video stream, in which a pair of an index corresponding to a piece of color information of the character color and an index corresponding to a piece of color information of the background color is continuously used, and updates the color lookup table by assigning a piece of color information of each gradation color to one of the indexes that is other than the indexes used in the period.