AC-3 (Dolby Digital)
Also known as: Dolby Digital, .ac3 file, AC3 audio
AC-3, better known as Dolby Digital, is a lossy audio format built for surround sound in movies, DVDs, and TV. It can carry up to 5.1 channels — five speakers plus a subwoofer — in a compressed stream small enough to fit alongside video. It is lossy, so some original detail is discarded.
- Lossy surround format (up to 5.1 channels)
- Standard on DVDs, Blu-ray, and digital TV
- Usually an audio track inside video
Surround sound, compressed
AC-3 is a lossy format whose job is to pack multichannel audio efficiently. A 5.1 mix would be huge if stored uncompressed; AC-3 squeezes those channels down so they fit on a DVD or in a broadcast stream while still driving a surround system.
It typically appears as the audio track inside video — on DVDs, Blu-rays, digital TV, and many video files — rather than as a standalone music file.
Playback and extracting
Home-theater receivers, TVs, and most media players decode Dolby Digital, but phones and basic players sometimes cannot, and stereo headphones can only fold the channels down to two.
If you only want the audio from a video, or need a plain stereo file that plays on any device, extract and convert the track to MP3.