Patent ID: 8184702

Claim:
A method for performing hierarchical B picture-based coding on a video sequence, the method comprising the steps of: (a) for each predetermined 2 N -frame-sized GOP of the video sequence, (a1) encoding the 2 N frame-sized GOP of the video sequence based on each of the different GOP sizes from the maximum size, 2 N , to the minimum size, 2 M (M is an integer between 1 and N) and selecting at least one sub-GOP based on the encoding result by (a1-i) comparing the difference values obtained from the encoding based on each of the different GOP sizes from 2 N to 2 M and, if the difference value obtained from the encoding based on the 2 N -sized GOP unit is the smallest, selecting the 2 N -sized GOP as a sub-GOP; and (a1-ii) if the difference value obtained from the encoding based on the 2 N -sized GOP is not the smallest, after decreasing N by 1 (i.e., N=N−1), selecting two 2 M -sized GOPs as the sub-GOPs if N has the same value as M, and repeating steps (a1-i) and (a2-ii) for each of the front 2 N frames and the rear 2 N frames, if N does not have the same value as M; and (a2) generating a bitstream by encoding the 2 N -frame-sized GOP based on the at least one selected sub-GOP; (b) decoding each 2 N frame-sized GOP bitstream; and (c) providing 1/L temporal scalability for each predetermined 2 N frame-sized GOP bitstream by: (c1) initializing “k” to 0 (k is an integer); (c2) initializing “FrameNum” to 2 N ; (c3) detecting whether there is a low-frequency frame in a bitstream from FrameNum th frame to L th frame in the reverse direction, and decreasing Frame Num by L; (c4) based on the result of detecting in the step (c3), (c4-i) increasing the value of k by 1, if there is no low-frequency frame, and (c4-ii) selecting the low-frequency frame detected first in the reverse direction if there is a low-frequency picture and, if the value of k is not 0, further selecting subsequent k number of high-frequency frames and then reinitializing k to 0; and (c5) repeating the steps (c3) and (c4) until FrameNum reaches 0, and finally selecting 2 N /L number of frames.