Compression methods can work lossless or lossy. Lossless compression consists of reducing the content of the information in such a way that it can be reproduced exactly when it is reproduced. With this method, only clearly redundant databases are compressed without any information being modified or deleted. The reproduction is one hundred percent of the original. Lossless compression is used, for example, in text compression, audio compression, or image compression.
With lossless compression, data is reduced by using statistical frequencies. For example, when compressing text, letters that appear more frequently, such as “e”, are assigned short codes, and letters that appear rarely, such as “y”, are assigned long codes. And with image compression, only the differences between two pixels are saved. With lossless compression, unlike lossy compression, only significantly lower compression rates can be achieved.
One of the most popular lossless compression methods is the ZIP file format, which displays text and graphics in different file formats compressed with extremely high compression rates. Other known methods include the RAR file format, Huffman encoding, the LZW algorithm, Run Length Encoding (RLE), and a JPEG mode.
With lossless predictive audio compression (LPAC) and lossless transform audio compression (LTAC), there are two methods for audio compression which are considered in MPEG-4 as MPEG-4 audio lossless encoding (ALS ). Other lossless compression methods include OptimFrog, Monkeys Audio (APE), Free Lossless Audio Codec (FLAC), and Apple Lossless Audio Codec (ALAC).
