What Is a Codec and What Does It Do

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Edited by Ben Jacklin

In the early days of the Internet, baud rate was the hot topic thanks to the slow download speeds; the transfer of large video and audio files was frustrating at the least, and practically impossible for those poor 300- or 600-baud modem owners. Even as transfer speeds picked up, so did the lengths and quality of movie and music files, constantly straining the capacity of your computer, your ISP, and the Internet as a whole. Great strides have been made since then, and much of the thanks goes to a little tool called codec. But what is a codec used for, how do codecs work, and what does codec stand for?

A codec definition

How do you define codec and what does codec mean? Codec is short for "coder/decoder" and it is a computer program with the ability to both compress and decompress multimedia files, making large file transfers possible without excessive delays (uncompressed multimedia files can take up to five times longer to download). However, this codec definition is rather simplistic; just as there is more than one computer operating system, it should come as no surprise that there are multiple codecs out there from which to choose. Simply saying, "I can't play my multimedia file, so I need a codec," doesn't answer the next logical question: "Which codec do I need?"

You are likely already using some of the more common codec formats, like:

  • MP3 – this is an early and still common format developed by The Moving Pictures Expert Group (hence the name "MPEG" which then shortened to MPG before settling on MP3), for music files that supports more audio channels and defines extra bit-rates.

  • WMA – originally developed by Microsoft for the Windows Media Player, WMA (Windows Media Audio) functions as both an audio format and audio codec.

  • RealVideo – this suite of video compression formats by RealNetworks was the first to accommodate multiple operating systems (Windows, Mac, Linux, Solaris, and even some mobile systems).

  • RealAudio – another RealNetworks product, this codec package allows users to compress a range of formats from low bit-rate (for dial-up modems) to high fidelity for top quality music output (supports Android, Microsoft Windows, Linux, macOS, Symbian, Solaris, Palm OS).

  • DivX – this codec developer, DivX, uses the company name for its product (smartly solidifying their name recognition in the codec arena) and supports video file formats such as AVI, MKV, HEVC, and, of course, DivX.

  • XviD – the developer, XviD, offers a codec that boasts a high compression rate of up to 200 to 1 (meaning a 100 GB file can be squeezed down to 500 MB).

This isn’t a comprehensive list of codecs that includes all streaming media, video conferencing, live speech, screen capture, and audio/video formats: there are scads of other codecs that have been developed. And this leads us to codec packs and their function.

Using codec packs

Sometimes your best bet is to grab a codec pack that stuffs a bunch of different codecs into one easy package. It may seem like overkill since you will end up with codecs you likely will never use, but it saves you time and frustration when searching for an arcane codec. Following are examples of some of the more popular and reliable codec packs available today:

  • CCCP – short for Combined Community Codec Pack, the CCCP comes in both a 32-bit and 64-bit format, along with CCCP Insurgent that will scan your system and identify installed codecs (and disable them if need be); many of the included codecs work for files retrieved through P2P programs like BitTorrent.
  • X Codec Pack – guaranteed to be both adware- and spyware-free, the X Codec Pack supports both 32- and 64-bit Windows operating systems and provides a small file size for fast downloads but still loaded with most essential codecs.
  • K-Lite Codec Pack – users can select from four different K-Lite Codec Pack bundles: the Basic Pack is perfect for DivX and XviD formats; the Standard Pack (most popular) covers most common file formats; the Full Pack gives users more codecs and encoding support; and the Mega Pack gives you the whole kit and kaboodle, including the Media Player Classic (for Windows only).

How codecs work

As the name implies, a codec performs two jobs: first, it compresses the size of the audio or video file, and second, it decompresses it as needed. All codecs employ an algorithm to accomplish this feat of decreasing large file sizes with the ability to later retrieve and display the data with similar quality as was originally recorded. However, this does not mean there is a "default" algorithm for performing the compressing of file sizes; each codec utilizes its own technology for creating the ideal algorithm for given applications. Furthermore, each codec can choose to encode files in one of two methods: lossy or lossless compression.

Lossy compression works by removing extraneous bits of information that do not impact the overall quality of the content. For instance, an MP3 music file can use lossy compression quite effectively by extracting sounds that cannot be heard by the human ear and consequently barely affects the quality of the overall sound. Another example is a JPG image file; it too deletes excess information or converts such information in a palatable context; for instance, a true picture with a full blue sky will generate many gradients of blue but can be easily reduced to one or two shades of blue. In lossy compression, the user typically can select the extent of the file compression technique, but higher compression (resulting in smaller file sizes) produces lower-quality content; a user may resort to trial and error to determine the best compression percentage while retaining an acceptable quality of content.

Lossless compression is geared more towards preserving content quality, meaning file sizes will not be as small as under lossy compression, but no valuable data is tossed out in the compression process; instead, compression is accomplished by removing redundancy. While this sounds very much like removing data in lossy compression, it actually converts the data to logical subunits. Here is an explanation of how lossless compression can work.

Assume you have content with the following string of characters included: "aaaaaaabbbccccccddeeeeeeeee" (which works out to a string of 7 a's in a row, followed by 3 b's, then 6 c's, 2 d's, and 9 e's). Lossless compression would convert that information to "a7b3c6d2e9" by reducing the string from a size of 27 characters to just 10 characters (it describes each consecutive group of characters by the character and number of identical characters following it, so "a7" equals "aaaaaaa"). The beauty of lossless compression is that the original data can always be recovered and used when needed.

Why would someone want to reverse the compression of a large file? Professional photographers, for example, want their RAW files intact, perhaps for professional printing of an oversize picture, but also want to share a smaller, lower quality image on their social media platforms for marketing purposes. By employing lossless compression, the original work can be presented in an informal context (i.e., on Pinterest) while also available for detailed editing without losing one pixel of data.

Codecs and video players

While codecs have uses outside video players, top video converters make the best use of codecs, meaning you can convert content you have downloaded in any format. With Movavi Video Converter, there is so much more you can accomplish: in addition to smooth and easy video conversion to over 180 formats (even HD), you can create audio files from video clips, snag pictures from your favorite screen clips, and even convert to any platform, any format, any time.

Oh, and all that knowledge you just gained about codecs? That (and so much more) has been utilized to the max in Movavi Video Converter; yep, the codecs you need to do all this are already included!

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