Koodekkiä

Koodekkiä, the Finnish term for codec, refers to a device or software that compresses and decompresses digital media streams. Codes are used to reduce the amount of data required to store or transmit audio or video, while preserving as much quality as possible within the chosen trade-off.

In practice, codecs are categorized by media type (video, audio, or data) and by whether they are lossy or lossless. They encode input data using transformations, quantization, and entropy coding to produce a compressed bitstream; the decoder reverses this process to reconstruct the original or a close approximation.

Common video codecs include H.264/AVC, H.265/HEVC, VP9, and AV1. Common audio codecs include MP3, AAC, Opus, and FLAC (lossless). Codecs are often used with container formats such as MP4 or MKV, which hold one or more encoded streams.

Licensing is a consideration: many codecs are patented and require licenses for commercial use. Some codecs, such as AV1 and Opus, are designed to be royalty-free, while others, like H.264 or MP3, are patented and may involve licensing through patent pools. Open-source implementations exist, for example x264, libvpx, and FFmpeg components.

The concept emerged during the rise of digital audiovisual standards in the 1990s with MPEG and others; the term "codec" is a contraction of coder-decoder. Codecs have been central to digital media distribution, streaming, and modern video conferencing.

See also: codecs, container formats, MPEG, AV1, Opus.