Video decoder

A video decoder is an electronic circuit, often contained within a single integrated circuit chip, that converts base-band analog video signals to digital components video. Video decoders commonly allow programmable control over video characteristics such as hue, contrast, and saturation. A video encoder performs the inverse function of a video decoder; it converts raw (uncompressed) digital video to analog video.

The input signal to a video decoder is analog video that conforms to a standard format such as NTSC or PAL. The output digital video may be formatted in various ways, such as 8-bit or 16-bit 4:2:2, 12-bit 4:1:1, or BT.656. Usually, in addition to the digital video output bus, a video decoder will also generate a clock signal and other signals such as:

Video codec

A video codec is an electronic circuit or software that compresses or decompresses digital video. It converts raw (uncompressed) digital video to a compressed format or vice-versa. In the context of video compression, "codec" is a concatenation of "encoder" and "decoder"—a device that only compresses is typically called an encoder, and one that only decompresses is a decoder.

The compressed data format usually conforms to a standard video compression specification. The compression is typically lossy, meaning that the compressed video lacks some information present in the original video. A consequence of this is that decompressed video has lower quality than the original, uncompressed video because there is insufficient information to accurately reconstruct the original video.

There are complex relationships between the video quality, the amount of data used to represent the video (determined by the bit rate), the complexity of the encoding and decoding algorithms, sensitivity to data losses and errors, ease of editing, random access, and end-to-end delay (latency).