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What are Codecs?

Codecs are algorithms or implementations that encode and decode audio, video, or image data. Encoding commonly reduces storage or transmission size, while decoding reconstructs data for playback or editing.

How Codecs work

A codec defines a reversible or intentionally lossy mapping between media samples and a coded representation, often alongside profiles and levels that restrict optional tools and decoder demands. The encoder chooses how aggressively to approximate the source; the decoder follows the resulting bitstream syntax. Implementations may run in software or dedicated hardware and can differ substantially in speed and compression efficiency. Codecs sit inside capture, conferencing, editing proxies, distribution, and archival pipelines.

Key facts

  1. Lossless codecs reproduce decoded samples exactly, whereas lossy codecs discard information according to a model of perceptual importance and cannot restore the original samples.
  2. A profile selects a permitted tool set and a level bounds resource requirements such as picture size or decoding rate; codec-name support alone is therefore insufficient.
  3. Inter-frame video codecs depend on reference pictures, so corruption or packet loss can affect later frames until recovery at a suitable random-access point.

When Codecs matter

Choose a codec by balancing quality, compression efficiency, latency, licensing, and target-device support. A more efficient codec may increase processing cost or exclude older browsers and hardware decoders.

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