Overview MPEG Moving Picture Experts Group Known as
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Overview • MPEG – – – – Moving Picture Experts Group Known as ISO/IEC Standard , ISO 11172 System, Video, Audio 1. 2 Mbits/sec, 352 x 240 resolution at 30 Hz is often used Video quality is comparable to VHS Random access, GOP(group of pictures) Realtime decoding For storage media; CDROM, DAT(Digital Audio Tape) 2021 -12 -29 제어인식연구실 2
MPEG Decoding System • MPEG – System : Synchronization – Video – Audio Figure 1 : MPEG Decoding System 2021 -12 -29 제어인식연구실 3
MPEG digital video coding Technique • Intra-frame coding technique – Spatial correlation between nearby pels within same image – DCT on image blocks of 8 x 8 pels • Inter-frame coding technique – Temporal prediction, motion compensated prediction between frames • Sub sampling and Interpolation – 4: 2: 0 format 2021 -12 -29 제어인식연구실 4
Intra-frame coding technique • DCT • Quantize • Zigzag scan Figure 2 : Variance distribution of DCT-coefficients 2021 -12 -29 제어인식연구실 Figure 3 : Zigzag scan order 5
Inter-frame coding technique • Block size : 16 x 16 • Search Window • Motion Vector Figure 4 : Block matching approach for motion compensation 2021 -12 -29 제어인식연구실 6
Subsampling and Interpolation • Sub sampling and Interpolation – The human eye is more sensitive to changes in brightness than to chromaticity changes – Divide the images into YUV components – 4: 2: 0 format Figure 5 : B picture encoding procedure 2021 -12 -29 제어인식연구실 7
Picture type • I Picture (Intra) – 프레임 내 부호화 영상 – GOP(Group of Pictures)의 독립성 확보 • P Picture (Predictive) – 프레임간 순방향 예측 부호화 – 원화상과 같은 순서로 부호화 • B Picture (Bi-directionally) – 쌍방향 예측 부호화 • D Picture – DC only, Fast Forward & Fast Rewind 2021 -12 -29 제어인식연구실 8
I Picture Figure 6 : I picture encoding procedure 2021 -12 -29 제어인식연구실 9
P Picture Figure 7 : P picture encoding procedure 2021 -12 -29 제어인식연구실 10
B Picture Figure 8 : Test picture (previous/current/future) Figure 9 : B picture encoding procedure 2021 -12 -29 제어인식연구실 11
Picture coding/display order Figure 10 : A group of consecutive pictures in video sequence 2021 -12 -29 제어인식연구실 12
Figure 11: (A) Frame at time instance N to be coded. 2021 -12 -29 제어인식연구실 13
Figure 11: (B) Frame at instance N-1 used for prediction of the content in frame N (note that the motion vectors depicted in the image are not part of the reconstructed image stored at the encoder and decoder). 2021 -12 -29 제어인식연구실 14
Figure 11: (C) Prediction error image obtained without using motion compensation - all motion vectors are assumed to be zero. 2021 -12 -29 제어인식연구실 15
Figure 11: (D) Prediction error image to be coded if motion compensated prediction is employed. 2021 -12 -29 제어인식연구실 16
MPEG video sequence Figure 12 : MPEG Video sequence Figure 13: Macroblock 2021 -12 -29 제어인식연구실 17
Reference • • • 정제창, 그림으로 보는 최신 MPEG, 1997 http: //www. image. cityu. edu. hk/~stshchu/project/Progress. Reports_1. htm http: //wwwam. HHI. DE/mpeg-video/papers/sikora/mpeg 1_2. htm http: //www. c-cube. com/technology/mpeg. html http: //bmrc. berkeley. edu/projects/mpeg/faq/mpegfaq. html ISO 13818 -2 2021 -12 -29 제어인식연구실 18
