Flashcards
Compression
Cards in this deck (10)
- 1Explain what is meant by compressionAn operation performed on a file/piece of data to reduce its size
- 2Advantages of compressionCan transfer large files over smaller bandwidths
Can increase data transfer speed - 3Lossy compressionRemoval of unnecessary or non-essential information
This information will not be recovered on decompressing the file
Overcompressing can reduce the quality of data
Can massively reduce size of files e.g. MP3 files are around 10% of their original uncompressed size
Used primarily for audio/video/images - 4Lossless compressionAll information is retained
Can recover the original data exactly
Quality preserved
Compressed files tend to be larger than lossy compression
Used primarily for text - 5Run-Length Encoding (RLE)Replaces strings of repeated pixels with their value and the number of repetitions
- 6Advantages of RLELossless, so can recover original file exactly and preserve its quality
Can reduce file size - 7Disadvantages of RLESignificant results are only possible for large files
Can increase file size if the file has few repeats - 8Dictionary-based compressionReplaces words or repeated strings of characters with a code
The code is stored in a dictionary sent with the message - 9Advantages of dictionary-based compressionLossless - will preserve file quality exactly so could be used for text
- 10Disadvantages of dictionary-based compressionDictionary could be larger than the original message
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- A level OCR A level Computer Science (Topic 4 - Exchanging Data) Flashcards on Compression, created by James Norman on 28/01/2020.
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- James Norman
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