C.3.7+Use+of+decompression+software+in+transfer+of+information


 * Compression:
 * data encoded using algorithms
 * encoding data using fewer bits
 * makes it move faster
 * reduces resource usage —> bandwidth wise
 * however requires hardware/software
 * less bits per second —> have to get rid of information because not enough storage
 * Characteristics of data
 * importance of data / sensitivity — safety (encryption)
 * speed
 * cost
 * transmission reliability
 * hardware:
 * ethernet cable / wireless
 * device with NIC (Network Interface Controller)
 * modem
 * router
 * Decompression Software
 * evaluate different types of decompression software
 * Lossless
 * data compressed without loosing any data
 * decompression — every bit remembered
 * identifies and eliminates redundancy
 * When used?
 * for important data —> like spreadsheets about money, sound, etc.
 * Lossy
 * gets rid of unnecessary information
 * part of data lost — used when this loss not prominent
 * When used?
 * for data not as important, or where difference not needed
 * e.g. YouTube videos
 * Real World Situations
 * (team speak)
 * allowed fast transferring of data via the internet, thus news shared immediately —> able to interfere with “history"
 * however, now everybody uploading —> clogs internet with useless stuff
 * makes information move more rapidly
 * more comfortable
 * .raw — plain data
 * dataloss depends on file format
 * seeing it depends on raw file
 * gif can only take 265 colours —> gif compression reduces amount of colours
 * jpeg —> at lowest quality —> pixelated —> takes 8x8 pixel squares and takes average colour —> stores difference between average and real
 * audio
 * mp3 — filters out frequency that doesn’t interfere with perception of sound
 * if bits per second reduced, then sound like robot
 * **3.1.8 Explain why the speed of data transmission across a network can vary.**
 * many users transmitting at the same time — bandwidth reduced
 * interference from outside causing corruption of packets —retransmission needed
 * **3 3.1.9 Explain why compression of data is often necessary when transmitting across a network. 3 S/E, INT Compression has enabled information to be disseminated more rapidly.**
 * compression —> faster transmitting
 * however, also more data transmitted now thus need compression to get all things across
 * **EXAMPLES**
 * gif
 * only stores 256 colours
 * has a zip compression in it (checks for redundancy)
 * diffusion —foggy/unclear
 * pattern — patterned —> usually nicer
 * jpeg
 * almost similar but only about 10% file size of original
 * takes 8 by 8 pixels calculates average and stores average and then difference between original and average
 * digital cameras
 * file format big

Created By: Lucie Magister Last update: 19/03/2015

Sources:
 * Classnotes.