mpeg: a video compression standard for multimedia applications didler le gall
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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. - PowerPoint PPT PresentationTRANSCRIPT
MPEG:A Video Compression Standard
for 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
Discrete Cosine Transform (DCT)
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
0 – black255 – white
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 – black255 – 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
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
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
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.tu-chemnitz.de/~jan/MPEG/HTML/mpeg_tech.html)