Compression artifact
These compression artifacts appear when heavy compression is applied. It occurs often in common digital media, such as DVDs, common computer file formats such as JPEG, MP3 and MPEG files. It also occurs in some other alternatives to the compact disc like the as Sony's MiniDisc format. Uncompressed media (such as on Laserdiscs and WAV files) or losslessly compressed media (such as FLAC or PNG) do not suffer from compression artifacts.