Data Compression

Data compression refers to the reduction of the amount of space needed to store a piece of data by using fewer bits. Data compression is measured by compression ratio, which is the size of the compressed data divided by the size of the original data. The less ratio, the less space a file takes.

How Data Compression Works?

(Lossy Compression Definition)

Data compression technique can be lossy or lossless. Lossy compression involves information loss while lossless compression does not. For example, database, emails, spreadsheets, office documents, and source code are compressed losslessly; images, videos, and audios usually use lossy compression.

Real-life Example: lossy compression removes some colors pixels to reduce the size. However, in lossless compression, since come pixels contain the same color, lossless compression technique uses algorithm to remember the coordinate of same colors instead of remembering every pixels. Then the size become smaller. Later, information will be decompressed losslessly in other computers. I just described the process of pictures’ compression. Video compressions work in the similar way, the only difference is that a picture is break down into pixels while a video is break down into frames.

Why compress?

• Speed: All networks have a limited bandwidth which means the maximum transmission capacity.
• Encryption / protection: For example, file format like rar. and zip. can guarantee the security of files by allowing users to add passport to files.
• File transfer
• Media file transfer: For example, live video streaming transfer
• Backups / archiving: Backup data is compress losslessly because database info should always be smaller than their original size.

Encoding

• Audio encoding
• Image encoding
• Video encoding
• File Compression

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Personal Reflection: Before this lesson, I only know that when I compress a file, it will be smaller than its original size. Now I understand how the sizes of files become smaller after compression. When some information are removed out, the size of a file will be less but some information are lost (lossy compression). When the computer uses algorithm to remember some information before removing those information, and later show those information back during decompression process, no information will be lost (lossless compression).

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Works Cited

“Lossy Compression Definition”. PC Magazine Encyclopedia, 2016, http://www.pcmag.com/encyclopedia/term/46335/lossy-compression.

“Encoding Audio And Video”. BBC Bitesize GCSE Computer Science, 2016, http://www.bbc.co.uk/education/guides/z7vc7ty/revision/4.