MPEG MPEG : Motion Pictures Experts Group MPEG : ISO Committee Widely Used Video Compression Standard

MPEG Types MPEG 1 : For lower resolution images Bit streams upto 1.5Mbps MPEG 2: Support higher resolution images Bit streams of upto 15Mbps MPEG 4: Support interactivity Composed of tools, algorithms, profiles, MSDL (MPEG Syntax Description Language)‏

MPEG Frame Types

Coding of Frames I-Frame : Intra-Frame ; coded independently P-Frame : Predicted Frame ; uses recently compressed I- or P-Frames B-Frame : Bidirectional Frame; uses both past and future I- or P-Frames

MPEG Encoder

Encoder Compress I-Frames Compress P-Frames (Immediately following I-Frames)‏ Compress B-Frames between I- and P-Frames Compress second P-Frame based on First P-Frame Compress B-Frames between first and second P-Frames

Encoder I-Frame : Compression very similar to baseline –JPEG No Motion Estimation P-, B-Frame : Use Motion Estimation

MPEG Decoder

Decoder Order of frames arriving at decoder different from the order of display Ex: -I 1 P 4 B 2 B 3 P 7 B 5 B 6 P 10 B 8 B 9 P 13 B 11 B Decoder needs 2 buffers for motion compensation Previous Buffer Future Buffer

Decoder Decompress I 1 ; Place in previous buffer Decompress P 4 using I 1 ; Place in future buffer Decompress B 2 and B 3 using these buffers Display Frames as soon as the buffers are full

Syntax Layers in MPEG –1

Macroblocks in MPEG-1

Profiles and levels in MPEG –2