Codec

A codec, short for coder-decoder, is a device or software that encodes and decodes digital data streams. In practice, a codec refers to both the algorithm used to compress data and the implementation that performs encoding and decoding. A encoder converts raw media into a compressed bitstream, and a decoder reconstructs the original media for playback or processing. Codecs may be implemented in hardware or software and are used to reduce bandwidth and storage requirements while preserving an acceptable level of quality.

Codecs are widely used for audio, video, and other media. They can be lossy, which sacrifices some information to achieve smaller file sizes, or lossless, which preserves exact data. Common audio codecs include MP3, AAC, Opus, and FLAC; common video codecs include H.264/AVC, H.265/HEVC, VP9, and AV1. Some codecs are patented and require licensing, while others are open or royalty-free, such as Opus for audio and AV1 for video.

Codecs and containers are distinct concepts. A container (for example MP4 or MKV) holds encoded streams and metadata, whereas the codec defines the method used to compress and reconstruct the data. For successful playback, the sender and receiver must support the same codec.

Codecs can be deployed in hardware, software, or hybrid forms. They underpin streaming services, video conferencing, broadcasting, and media archiving. Performance factors include bitrate, quality, latency, and device compatibility. In real-time communications, low-latency codecs (such as Opus or G.711 variants) and hardware acceleration are particularly important.