.ac3 File — Dolby Digital Audio

AC3 is the file format for Dolby Digital (originally Dolby AC-3) audio, a perceptual coding system developed by Dolby Laboratories. Dolby Digital supports up to 5.1 channels of surround sound at bitrates from 32 to 640 kbps, with 384 or 448 kbps being typical for film and broadcast. The codec uses psychoacoustic modeling to reduce data rates while maintaining perceived audio quality, applying modified discrete cosine transform (MDCT) coding independently to each channel. AC3 is the standard audio format for DVD-Video, many Blu-ray discs, digital television broadcasts (ATSC in North America), and streaming services. The format is essential to home theater systems, where it provides the immersive surround sound experience with discrete front, center, surround, and subwoofer channels. Dolby Digital Plus (E-AC-3) extends the original codec with support for up to 7.1 channels and improved coding efficiency. AC3 files are commonly extracted from DVD and Blu-ray sources or found in digital movie files alongside video streams in MKV or AVI containers.