Lec1 - CAP5015-01 Multimedia Compression on the Internet...

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CAP5015-01 Multimedia Compression on the Internet University of Central Florida School of Electrical Engineering and Computer Science
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Why Data Compression? Decrease storage requirements Strict bandwidth bound of communication channels Effective use of communication bandwidth; reduce amount of data without loosing information Improves program execution speed by reducing disk access times Increased data security Multimedia data on information superhighway Growing number of “killer” applications. (Digital Library, Massive text databases like TREC, web sites like google, medical imaging, satellite images, journals(IEEE,ACM), Newspapers etc. etc.)
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Data Compression Metrics For data transmission application, the goal is speed. Speed of transmission depends upon the number of bits sent and obviously data compression helps the situation. Utilization of the available bandwidth is another goal of data compression. The time required for the encoder to generate the coded message, and the time required for the decoder to recover the original message are also important factors. In a data storage application, although the degree of compression is the primary concern, it is nonetheless necessary that the algorithm be efficient in order for the scheme to be practical.
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Approximate Bit Rates for Uncompressed Sources (I) Telephony 8000 samples/sec X 12 bit/sample (Bandwidth=3.4kHz) = 96 kb/sec --------------------------------------------------------------------------- Wideband Speech 16,000 s/s X 14 b/s = 224 kb/sec (Tele.audio bw~7 kHz) --------------------------------------------------------------------------- Compact Disc Audio 44,100 s/s X 16 b/s X 2 channels (Bandwidth~ 20kHz) = 1.41 Mb/sec
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Large Image Files low-resolution, TV quality, color video image: 512x512 pixelsX24( 8 bits/pixel, and 3 colors) =6.3 Mb/image . 24 X36 mm (35-mm) negative photograph scanned at 12 micron resolution 3000X2000 pixels/color, 8 bits/pixel, and 3 colors gives 144 Mbits. 14 X17 inch radiograph scanned at 70 micron: 5000 X 6000 pixels, 12 bits/pixel gives 360Mbits. Medium size hospital generates terrabytes each year. LANDSAT Thematic Mapper scene: 6000 X 6000 pixels/spectral band, 8 bits/pixel, and 6 nonthernmal spectral bands :1700 M bits Computer graphics: lightfield representation of Michelangelo's David: hundreds of megabytes
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Approximate Bit Rates for Uncompressed Sources Video 640x480 color pixel X 24 bits/pixel X 30 images/sec=221Mb/s CIF (Videoconferencing: 360x288): 75Mb/sec CCIR(TV: 720x576): 300 Mb/sec HDTV (1260x720 pixels X 24 b/p X 80 images/sec): 1.3 Gb/sec Gap between available bandwidth and the required bandwidth can be filled using compression !
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Why Compression now?
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Lec1 - CAP5015-01 Multimedia Compression on the Internet...

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