Compression is a way to reduce the file size of video data (either a file or stream) while maintaining acceptable quality. Lossy compression means that some quality is lost; Lossless compression retains full quality.
There are many ways to compress video, all involving a codec (compressor/decompressor). To view a video compressed with a particular codec, you need to have that codec installed. In most cases this happens without you being aware of it, for example:
- DVD players have the appropriate codecs built-in.
- Computer operating systems have many common codecs pre-installed. New codecs can be downloaded automatically or manually.
The following compression ratios are often used when compression video data: