A video codec is a device or software that enables video compression and/or decompression for digital video. The compression usually employs lossy data compression. Historically, video was stored as an analog signal on magnetic tape. Around the time when the compact disc entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge.

 

Digital video codecs are found in DVD (MPEG-2), VCD (MPEG-1), in emerging satellite and terrestrial broadcast systems, and on the Internet. Online video material is encoded in a variety of codecs, and this has led to the availability of codec packs - a pre-assembled set of commonly used codecs combined with an installer available as a software package for PCs.Encoding media by the public has seen an upsurge with the availability of DVD-writers. Since commercially available DVDs are usually dual-layer, and hence bigger than the more common single layer writable DVDs, it is often the case that the material has to be compressed again, sacrificing quality so that the media will fit onto a single layer disc.