Editing Lossy compression (section)

==Comparison==

The advantage of lossy methods over [[Lossless compression|lossless]] methods is that in some cases a lossy method can produce a much smaller compressed file than any lossless method, while still meeting the requirements of the application. Lossy methods are most often used for compressing sound, images or videos. This is because these types of data are intended for human interpretation where the mind can easily "fill in the blanks" or see past very minor errors or inconsistencies – ideally lossy compression is [[Transparency (data compression)|transparent]] (imperceptible), which can be verified via an [[ABX test]]. Data files using lossy compression are smaller in size and thus cost less to store and to transmit over the Internet, a crucial consideration for [[streaming video]] services such as [[Netflix]] and [[streaming audio]] services such as [[Spotify]].

===Transparency===
{{further|Transparency (data compression)}}
When a user acquires a lossily compressed file, (for example, to reduce download time) the retrieved file can be quite different from the original at the [[bit]] level while being indistinguishable to the human ear or eye for most practical purposes. Many compression methods focus on the idiosyncrasies of [[human physiology]], taking into account, for instance, that the human eye can see only certain wavelengths of light. The [[psychoacoustic model]] describes how sound can be highly compressed without degrading perceived quality. Flaws caused by lossy compression that are noticeable to the human eye or ear are known as [[compression artifact]]s.

===Compression ratio===
The [[data compression ratio|compression ratio]] (that is, the size of the compressed file compared to that of the uncompressed file) of lossy video codecs is nearly always far superior to that of the audio and still-image equivalents.

* Video can be compressed immensely (e.g., 100:1) with little visible quality loss
* Audio can often be compressed at 10:1 with almost imperceptible loss of quality
* Still images are often lossily compressed at 10:1, as with audio, but the quality loss is more noticeable, especially on closer inspection.