Using codecs

A codec is software that is used to compress or decompress a digital media file, such as a song or video. Content creators use codecs because a compressed file takes up less storage space on your computer and can be transferred across the Internet more quickly and smoothly. When you play a digital media file, Windows Media Player uses a codec to decompress the file. Codecs are used to create and play nearly all music or video files on your computer or on Web sites.

A codec can consist of two components—an encoder and a decoder. The encoder compresses a file during creation, and the decoder decompresses the file so that it can be played. Some codecs include both components, while other codecs only include one. For example, if you install a DVD playback program on your computer, the program will likely install a codec that only includes an MPEG-2 decoder, which allows you to play the DVD on your computer. You would not be able to use the decoder to create your own DVD.

You are probably trying to play a file that uses a codec that is not on your computer. When you try to play a file that uses a codec that is not on your computer, the Player tries to download the codec from a Microsoft server. If the codec is available, the Player installs it on your computer and then plays the file. If the codec is not available on the server (for example, because the codec wasn't created by Microsoft), the Player displays a message that your computer is missing a codec. If you are connected to the Internet, the message usually has a Web Help button that you can click for more information. If the Player can determine which codec you are missing, when you click that button, a Help topic is displayed that contains a link to WMPlugins.com, a Web site that lists a number of codecs that are available to download. The MPEG-2 and DivX video codecs and the ACELP.net and Ogg Vorbis audio codecs are examples of codecs that are not included in the operating system or the Player by default. For more information, see How do I find a codec?

In some cases, the file you want to play uses a codec that isn't available or compatible with the Player. When that happens, the Player won't be able to play the file.

For information about how you can ensure that the Player will try to download codecs automatically, see Does the Player always try to download codecs automatically?

When trying to find the right codec for a particular file, you can use WMPlugins.com or other Web sites. Typically, you should start with WMPlugins.com first. Note that if you aren't able to find a codec on WMPlugins.com, it is possible that the codec you are looking for is not compatible with the Player, so you might not be able to use the Player for this particular file.

We recommend that you use caution when installing codecs that aren't listed on WMPlugins.com or Microsoft.com, such as the DivXNetworks Nimo or Tsunami codec packs. Incompatibilities are known to exist with some of the components in these codec packs that can cause serious playback issues in the Player and other players, lead to system corruption, and make it difficult for Microsoft Support to diagnose and troubleshoot playback issues. For these reasons, we strongly discourage you from installing these codec packs, and recommend that you remove them if you have installed them and are having problems with the Player. We recommend that you only install codecs, filters, or plug-ins from trusted, authorized sources, such as the Web site of the official supplier. Even then, we recommend that you use caution, because many codec suppliers offer minimal customer support. If your computer is running Microsoft Windows Millennium Edition or Windows XP, we recommend that you set a system restore point before installing any digital media components. This enables you to return to your original system configuration, if necessary. To learn more about security, see the Windows Media Player 11 or Windows Media Player 10 security statement.

  WMPlugins.com

  Other Web sites

It depends on several factors. To ensure the Player can try to download codecs automatically, you must have Internet Explorer 3.02 or later installed on your computer, maintain Internet access while playing the file, and your Internet security should be set to Medium. In addition, if your computer is running Microsoft Windows NT, Windows 2000, Windows XP Professional, or Windows Server 2003, you must be logged on as an administrator or as a member of the Administrators group. Finally, do the following:

There isn't an absolute way to do this, but the following are your best options:

Note that a file can be compressed by more than one codec. For example, one codec might be used to compress the audio portion of a file and another codec might be used to compress the video portion of a file. If you have the right audio codec installed on your computer but not the right video codec, when you play the file you'll probably be able to hear the sound but you won't be able to see the picture.

"Microsoft codec package" refers to the codec packages available on Windows Media Codec Download and Microsoft Download Center. The Microsoft codec package is made available for network administrators who want to put the codecs on hundreds or thousands of computers at once rather than having each person in the company download codecs individually. If you downloaded the Player yourself, the codecs that are in the Microsoft codec package were installed automatically, so downloading the package probably is not necessary and won't help resolve any codec-related issues you might encounter. Instead, try the steps outlined in How do I find a codec?

Installing codecs is not typically necessary if you are running Windows Media Player 10 or later because the latest Windows Media audio and video codecs were automatically installed on your computer when you installed the Player. However, if you think your codecs are corrupted or out of date, you can download and install the latest codecs from the Download Center.

No, although it can be confusing because they sometimes have the same name. You can think of a file format as a type of container. Inside the container is data that has been compressed by using a particular codec. For example, a file format such as Windows Media Audio contains data that is compressed by using the Windows Media Audio codec. However, a file format such as Audio Video Interleaved (AVI) can contain data that is compressed by any of a number of different codecs, including the MPEG-2, DivX, or XVid codecs. AVI files can also contain data that is not compressed by any codec. Consequently, you might be able to play some AVI files and not others, depending on which codecs were used to compress the file and which codecs you have installed on your computer. For the same reason, you also might be able to play the audio portion of an AVI file, but not the video portion.

You might be able to tell a file's format by looking at the file's extension (such as .wma, .wmv, .mp3, or .avi). However, there are limits to this approach. Many programs create files with custom file extensions. And it's possible for anyone to rename a file without changing the file's format. A file with the extension .mpg or .dvr-ms, for instance, is usually just an AVI file that has been compressed by using some version of an MPEG video codec.

All codecs make some tradeoff between sound or video quality, file size, and compatibility with non-Microsoft playback programs and devices. To compare codecs, click one or both of the following links:

Windows Media Audio and Windows Media Video are widely-used codecs that are flexible enough to suit the needs of most content creators and consumers. For example, the Windows Media Audio codec can be used to create very small files suitable for streaming talk radio over the Internet or very high-fidelity files that support multiple audio channels for use in high-end home theater systems. Likewise, the Windows Media Video codec can be used to create small files suitable for streaming short videos over the Internet or high-definition video suitable for projection in commercial movie theaters. For information about codecs you might use when creating digital media files, see Windows Media 9 Series Audio and Video Codecs.

If your digital camera produces MJPEG .avi files, install Microsoft DirectX 9.0, which includes an MJPEG decoder. To install DirectX 9.0, see DirectX Download.

If you do not find an answer to your question in this FAQ, try the following resources:

To find the error code identification number for a particular error message, on the error message, do one of the following:

For information about Windows Media Player error messages, see Troubleshooting Windows Media Player Error Messages.