Data compression or source coding refers to the process of encoding information using fewer bits, with the use of specific encoding schemes. Audio compression is a type of data compression that was designed to reduce the transmission bandwidth required by digital audio streams and also the storage size of audio files. Lossy and lossless algorithms are the audio compression algorithms that are implemented as audio codecs.
Information redundancy is reduced in both forms of compression with the use of methods like coding, pattern recognition and linear prediction. However, lossy algorithms provide greater compression rates and are therefore used in mainstream consumer audio devices. Lossy audio compression algorithms can be defined as the ones that do not retain every bit of data and only reproduce a signal that sounds more or less like the original.
The compression algorithm is used in a wide range of applications like MP1, MP2, MP3 and AAC. In addition to these, it is also used in video DVDs, digital television, satellite and cable radio, streaming media on the internet and terrestrial radio broadcasts. Lossy audio compression reduces perceptual redundancy by removing the irrelevant sounds with high frequencies or coded with decreased accuracy. It is achieved by hiding the noise generated by the bit savings in areas that cannot be perceived.
The compression parameters for most lossy compression schemes can be adjusted to achieve a target rate of data that is expressed as a bit rate. The use of this scheme may result in a perceived reduction of the audio quality from none to severe, depending on the bandwidth and storage requirements.
Lossy compression isn’t preferred for archival storage by many since the data that is removed during the compression cannot be recovered by decompression. For this reason, people use lossless compression for archival storage even when using lossy compression for portable audio applications.