Windows Media Encoder installs several audio and video codecs onto your computer. Codecs are also installed as part of the operating system and are sometimes added when you download files from the Internet. Windows Media Encoder can use any codec installed on your computer to encode ASF content; however, Microsoft Windows Media Player must have access to the same codec to decode your content. To ensure that your content can be decoded by Windows Media Player, choose codecs that are installed with Window Media Encoder.