Patent ID: 8085843
Filing Date: 2011-12-27
Classification: G11B,H04N

Abstract:
1. An MPEG-4 Part 14 (MP4) demultiplexer comprising: a frame-position calculating unit configured to select frames to be extracted among video frames of an MP4 file, according to information of a speed at which the MP4 file is to be played, and to calculate respective positions of the selected frames based on an address of a start frame of the MP4 file; a frame extracting unit configured to extract the selected frames from the MP4 file based on the calculated positions of the selected frames and respective frame-size information of the selected frames; and a memory including a stco box configured to store the address of the start frame of the MP4 file, a stss box configured to store respective frame numbers corresponding to intra-frames (I-frames) of the video frames, and a stsz box configured to store respective frame-size information of the video frames, wherein the frame-position calculating unit determines a number of predicted-frames (P-frames) to be extracted by determining a number of P-frames present between the I-frames based on a number of the I-frames stored in the stss box, according to the information of the speed at which the MP4 file is to be played, selects P-frames to be extracted according to the number of P-frames determined to be extracted, and calculates respective positions of the selected P-frames by using information of the start-frame address stored in the stco box and the frame-size information of the video frames stored in the stsz box, and the frame-position calculating unit selects the P-frames by skipping at least one P-frame in a succession of P-frames, when selecting the P-frames to be extracted.