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Learn about MPEG, a standard for video compression developed by the Moving Picture Experts Group in the late 1980s to address the high cost and interoperability issues in multimedia applications. Understand how the MPEG standard works, its key features, requirements, and compression techniques like Discrete Cosine Transform and Motion Compensation.
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MPEG:A Video Compression Standardfor Multimedia ApplicationsDidler 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
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 99 106 131 119 101 86 80 83 93 100 117 105 87 72 65 69 78 85 100 88 70 55 49 53 62 69 89 77 59 44 38 42 51 58 Discrete Cosine Transform (DCT) 0 – black 255 – white
DCT (cont’d) • The 64 (8 x 8) DCT basis functions • Superimpose multiples of these functions to simulate the original picture
700 90 100 0 0 0 0 0 90 0 0 0 0 0 0 0 -89 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 DCT (cont’d) 0 – black 255 – white
700 90 100 0 0 0 0 0 90 0 0 0 0 0 0 0 -89 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 DCT (cont’d) 700 90 90 -89 0 100 0 0 0 .... 0
Motion Compensation • I-Frame • Independently reconstructed • P-Frame • Forward predicted from the last I-Frame or P-Frame • B-Frame • forward predicted and backward predicted from the last/next I-frame or P-frame Transmitted as - I P B B B P B B B
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.tu-chemnitz.de/~jan/MPEG/HTML/mpeg_tech.html)