Download the AC3 filter, a software filter that allows media players to play audio files encoded using the Dolby Digital (AC-3) audio codec. This codec is commonly used in DVDs, HDTV broadcasts, and other digital media. You will note that the AC3 filter decodes the audio data. It then sends it to the sound card for playback. Then enabling the media player to play the audio correctly. This allows to play video files with AC3 audio codec and other such codecs.