What Is Video Compression?

Know the differences between lossy and lossless video compression formats

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Videos take up a lot of space — just how much varies widely depending on the video format, the resolution, and the number of frames per second that were chosen when the video was created.

Uncompressed 1080 HD video footage takes up about 10.5 GB of space per minute of video, but this varies with frame rate. If you use a smartphone to shoot your video, 1080p footage at the standard 30 frames per second takes up 130 MB per minute of footage, while 4K video takes up 375 MB of space for each minute of film.

Because videos take up so much space, and because bandwidth is limited, video files are almost always compressed before they are put on the web or downloaded from the web. Compression involves packing the file's information into a smaller space. This works through two different kinds of compression: lossy and lossless.

Lossy Compression Formats

Lossy compression means that the compressed file has less data in it than the original file. Images and sounds that repeat throughout the video might be removed to effectively cut out parts of the video that are seen as unneeded. In some cases, this translates to lower quality files because information has been lost, hence the designation "lossy."

However, you can lose a relatively large amount of data before you start to notice a difference (think MP3 audio files, which use lossy compression). Lossy compression makes up for the loss in quality by producing comparatively small files. For example, DVDs are compressed using the MPEG-2 format, which can make files 15 to 30 times smaller than the originals, but viewers still perceive DVDs as having high-quality pictures.

Most video files uploaded to the internet use lossy compression to keep the file size small while delivering a relatively high-quality product. If a video were to remain at its (in some cases) extremely high-quality file size, not only would it take forever to upload the content online, but users who have slow internet connections would have an awful time streaming the video or downloading it to their computers.

Although using a lossy compression format makes much smaller files, data is lost and cannot be restored.

Lossless Compression Formats

Lossless compression is exactly what it sounds like: the original and the compressed versions are nearly identical. None of the data is lost in the compression process. Lossless compression formats are not nearly as useful as lossy compression in many cases because files often end up being the same size as they were before compression.

Using lossless video compression might seem pointless because reducing the file size is the primary goal of compression. However, if the file size is not an issue, using lossless compression results in a perfect-quality picture.

For example, a video editor transferring files from one computer to another using an external hard drive might choose to use lossless compression to preserve quality while he's working. In this case, since the external HDD has enough free space to hold the huge video file, it's not a problem.

However, lossless compression probably wouldn't be used by someone who wants to upload a 2-hour-long, 4K video to a video streaming site. The file would be so large that it'd take a long to time to upload.

Lossless compression formats include Free Lossless Audio Codec (FLAC), Apple Lossless Audio Codec (ALAC), and Windows Media Audio Lossless (WMAL), among others.

When quality is what matters, not size, use a lossless compression format that is compatible with your intended usage.