Video codec and motion estimation method

A video codec, coupled to an outer memory storing a reference frame, comprising:

• an interface circuit to obtain in-chip data from the reference frame stored in the outer memory;
• an in-chip memory, storing the in-chip data, wherein the in-chip data comprises N rows of macroblocks of the reference frame, wherein N is a positive integer, and the size of the N rows of macroblocks is smaller than that of a storage space of the in-chip memory;
• a motion estimation circuit to obtain search window data from the in-chip data with a search window, and to perform a motion estimation process on a current macroblock according to the search-window data;
• and
• a controller to shift the location of the search window in the in-chip data, when the current macroblock is shifted, mark a location of a macroblock shifted out from the search window as an empty macroblock, and control the interface circuit to obtain an updated macroblock for replacing the empty macroblock in the in-chip memory from the reference frame stored in the outer memory.