What Is a Codec, and Why Do I Need It?

Codecs keep large video and audio files at manageable sizes

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A codec — the term is a mashup of the words code and decode — is a computer program that uses compression to shrink a large movie file or convert between analog and digital sound. You might see the word used when talking about audio codecs or video codecs.

Why Codecs Are Necessary

Video and music files are huge, which means they are usually difficult to transfer over the internet. To speed up downloads, mathematical codecs were built to encode, or shrink, a signal for transmission and then decode it for viewing or editing. Without codecs, downloads of video and audio would take three to five times longer than they do now.

How Many Codecs Do I Need?

There are hundreds of codecs in use on the internet, and you will need combinations that specifically play your files.

There are codecs for audio and video compression, for streaming media over the internet, speech, video conferencing, playing MP3s, and screen capture.

To make matters more confusing, some people who share their files on the web choose to use obscure codecs to shrink their files. This frustrates users who download these files but don't know which codecs to use to play them.

If you're a regular downloader, you'll probably need 10 to 12 codecs to play all the different types of music and movies you have.

Common Codecs

Some common codecs are MP3, WMA, RealVideo, RealAudio, DivX, and XviD, but there are many others.

AVI is a common file extension you see attached to lots of video files, but it is not in itself a codec. Instead, it is a container format that many different codecs can use. Hundreds of codecs are compatible with AVI content, so it can be confusing which codecs you need to play your video files.

How Do I Know Which Codec to Download and Install?

Because there are so many codec choices, codec packs are a convenient option. Codec packs are collections of codecs gathered into single files. There is debate over whether it is necessary to have a large group of codec files, but it certainly is the easiest and least frustrating option for new downloaders. 

Here are the codec packs you are the most likely to need:

  • CCCP (Combined Community Codec Pack) is one of the most comprehensive codec packages you can download. CCCP was put together by users who like to share and watch movies online, and the codecs it contains are designed for 99 percent of the video formats you experience as a P2P downloader. Consider CCCP if you think your computer needs updated codecs.
  • X Codec Pack is a sleek, all-in-one, spyware-free and adware-free codec collection that isn't a huge size, so it doesn't take long to download. X Codec Pack is one of the most complete assemblies of codecs needed to play all major audio and video formats.
  • K-Lite Codec Pack is well-tested and loaded with goodies. It lets you play all the popular movie formats. K-Lite comes in four flavors: Basic, Standard, Full, and Mega. If all you need is play are DivX and XviD formats, Basic does just fine. Standard pack is the most popular. It has everything an average user needs to play the most common file formats. Full pack, designed for power users, has even more codecs in addition to encoding support.

If you use Windows Media Player, it often tries to communicate to you the 4-character code of the specific codec it needs. Note this code and then visit FOURCC to obtain the missing codec. FOURCC's Samples page has some FAQs if you need more information on what's offered there.

Another option for getting codecs is to download media players that include them. Sometimes, a video or audio player installs important and common codecs when you first install the application. VLC is a great free media player that can play all sorts of file types.