Method and Apparatus for Coding Information
The invention provides a method and apparatus for coding information that is specifically adapted for smaller presentation formats, such as in a hand held video player. The invention addresses, inter alia, reducing the complexity of video decoding, implementation of an MP3 decoder using fixed point arithmetic, fast YcbCr to RGB conversion, encapsulation of a video stream and an MP3 audio stream into an AVI file, storing menu navigation and DVD subpicture information on a memory card, synchronization of audio and video streams, encryption of keys that are used for decryption of multimedia data, and very user interface (UI) adaptations for a hand held video player that implements the improved coding invention herein disclosed.
1 . A method for fast “YUV to RGB555” conversion, comprising the steps of:
providing a conversion table; and
calculating a table index as a function of three colors in YUV format;
wherein a conversion table cell represents a color in RGB555 format that corresponds to a color in YUV format.
2 . The method of claim 1 , wherein YUV format is represented as:
Index = ((U >> (8-BITS_U)) << (BITS_Y+BITS_V)) + ((V
>> (8-BITS_V)) << (BITS_V)) + (Y >> (8-BITS_Y))
where Y, U, and V are 8-bit color components in YUV format; and BITS_Y, BITS_U, BITS_V are the numbers of significant bits for each color: Y, U, and V.
3 . The method of claim 2 , wherein the number of indexes is (1<<(BITS_Y+BITS_U+BITS_V)), wherein the size of a cell is two bytes (high-order bit is unused), and wherein the size of said table is the number of indexes * 2, that is:
(1<<(BITS_Y+BITS_U+BITS_V+1)).
4 . The method of claim 3 , wherein the number of significant bits for the Y color component must be greater than number of significant bits for the U and V components.
5 . The method of claim 4 , wherein said color conversion table is organized to avoid cache misses during conversion of image in YUV4:2:0 format.