It is possible to compress many types of digital data in a way that reduces the size of a computer file needed to store it, or the bandwidth needed to transmit it, with no loss of the full information contained in the original file. The original data contains a certain amount of information, and there is a lower limit to the size of file that can carry all the information.
In many cases, files or data streams contain more information than is needed for a particular purpose. For example, a picture may have more detail than the eye can distinguish when reproduced at the largest size intended; likewise, an audio file does not need a lot of fine detail during a very loud passage. Developing lossy compression techniques as closely matched to human perception as possible is a complex task. Sometimes the ideal is a file that provides exactly the same perception as the original, with as much digital information as possible removed; other times, perceptible loss of quality is considered a valid trade-off for the reduced data.
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Lossy compression is a method that uses inexact approximations of the original data in a computer file. Techniques are used to reduce data size for storage, handling, and transmitting content.
Well-designed lossy compression technology often reduces file sizes significantly before degradation is noticed by the end-user. Even when noticeable by the user, further data reduction may be desirable (e.g., for real-time communication, to reduce transmission times, or to reduce storage needs).
Lossy compression is most commonly used to compress multimedia data (audio, video, and images), especially in applications such as streaming media and internet telephony. MP3s are an example of lossy compression.
For more information visit: https://en.wikipedia.org/wiki/Lossy_compression
Lossless data compression which does not degrade the data. This type of compression is typically required for text and data files, such as bank records and text articles. A very common format of lossless compression is a ZIP file.
When a lossless data file is decompressed all original data is available.
In many cases it is advantageous to make a master lossless file which is to be used to produce new compressed files; for example, a multi-megabyte file can be used at full size to produce a full-page advertisement in a glossy magazine, and a 10 kilobyte lossy copy can be made for a small image on a web page.
For more information visit: https://en.wikipedia.org/wiki/Lossless_compression