Video codec
A video codec is a piece of software or hardware that makes video or audio smaller. The word 'codec' is a blend between 'encoder' (thing that makes the video smaller) and 'decoder' (thing that puts video to the screen).
Compressed (smaller) data is usually put to a certain format. The data is normally "lossy" (the data lacks some details), which means that video that is put through a decoder is usually blurry or low quality. This is because there is not enough data to rebuild the video properly.
There are relationships between the quality of the video, the bitrate (amount of data used for video) and how complex the methods the codec uses. There is also a thought for latency (delay) between both ends. This is usually only worried about when playing video over the Internet.
History
changePreviously, video was stored on magnetic tape which has an analog signal until the introduction of the CD. The CD was the first time it made sense to store and play video in digital form. Because of the large size to store raw video, a method was needed to reduce the amount of data used.
In 1974, a compression method called DCT (short for discrete cosine transform) was made by Nasir Ahmed, T. Natarajan and K. R. Rao.
During the 1980s, some companies began to test DCT to store video which lead to the creation of the H.261 standard. The H.261 standard was the first time a video codec had been practical. It was developed by multiple companies such as Hitachi and Toshiba. DCT has been used by all of the big video coding standards since.
Some of the most popular standards for codecs have been the MPEG standards. MPEG-1 was made in 1991 and was made to compress VHS-quality video. It was improved in 1994 when MPEG-2 (sometimes called H.262) was made. It was made by lots of companies but the ones that helped the most were Sony, Thomson and Mitsubishi. MPEG-2 became the normal format for DVD and low quality digital TV. In 1999, MPEG-4 was released which was much better than previous video compression technology.
The most used codec, as of 2023 is called H.264. It was made in 2003 by lots of companies such as Panasonic and LG. H.264 is the main codec used for Blu-ray discs and is used on the Internet and TV.
H.264 has been improved by HEVC (sometimes called H.265) which was made by Samsung and JVC in 2013. Most things don't use HEVC because of the license.
There are also free codecs for video such as VP8 and VP9 which are used on YouTube and were made by Google.