MPEG A Video Compression Standard for Multimedia Applications

MPEG: A Video Compression Standard for Multimedia Applications Didler Le Gall

Goals • Reduce the high cost of video compression codecs • Resolve the critical problem of interoperability of equipment from different manufacturers • Come up with a standard within 2 years

MPEG • Stands for Moving Picture Experts Group (ISO-IEC) • Started in 1988 • Had to come up with a draft of the standard by 1990 • Received MPEG Proposal from mostly commercial companies

MPEG (cont’d) • MPEG-Video • MPEG-Audio • MPEG-System – Synchronization of audio and video

Requirements • • • A Generic Standard Random Access Fast Forward/Reverse Searches Reverse Playback Audio Visual Synchronization Robustness to Errors

Requirements (cont’d) • • Coding/Decoding Delay Editability Format Flexibility Cost Tradeoffs

MPEG-VIDEO Compression • Spacial Redundancy – Intraframe compression – DCT compression • Temporal Redundancy (i. e. motion compression) – Interframe compression

Discrete Cosine Transform (DCT) 0 – black 255 – white 120 108 90 75 69 73 82 89 127 115 97 81 75 79 88 95 134 122 105 89 83 87 96 103 137 125 107 92 86 90 131 119 101 86 80 83 117 105 87 72 65 69 100 88 70 55 49 53 89 77 59 44 38 42 99 106 93 100 78 85 62 69 51 58

DCT (cont’d) • The 64 (8 x 8) DCT basis functions • Superimpose multiples of these functions to simulate the original picture

DCT (cont’d) 0 – black 255 – white 700 90 100 0 0 90 0 0 0 -89 0 0 0 0 0 0 0 0 0 0 0 0

DCT (cont’d) 700 90 100 0 90 0 0 -89 0 0 0 0 0 0 0 0 0 0 0 0 0 700 90 90 -89 0 100 0 0 0. . 0

Motion Compensation • I-Frame – Independently reconstructed • P-Frame – Forward predicted from the last IFrame or P-Frame • B-Frame Transmitted as - I P B B B – forward predicted and backward predicted from the last/next I-frame or P-frame

Motion Prediction

Motion Estimation

Motion Estimation (cont’d)

Conclusion • Video quality better than VHS can be achieved with a bit rate of about 1. 5 Mbits/s • Does not handle higher resolution with small bit rate

References • MPEG Notes by Dale Kolosna • MPEG Compression Technique (http: //rnvs. informatik. tuchemnitz. de/~jan/MPEG/HTML/mpeg_tech. html)