AC-3 (Dolby Digital Audio)
AC-3 is Dolby's multichannel audio codec used in DVDs, Blu-ray discs, cinema, and broadcast television. It encodes up to 5.1 channels of surround sound at bitrates from 32 to 640 kbps. AC-3 is the standard audio format for home theater systems.
MIME Type
audio/ac3
Type
Binary
Compression
Lossless
Advantages
- + Industry standard for DVD and Blu-ray multichannel audio
- + Universal support in home theater receivers and players
- + Efficient 5.1 surround encoding at moderate bitrates
Disadvantages
- − Lossy compression — not suitable for production masters
- − Maximum of 5.1 channels (E-AC-3 extends to 7.1)
- − Not commonly used for music distribution
When to Use .AC3
Use AC-3 for DVD authoring, surround sound mixing, and home theater content where 5.1 multichannel audio is required.
Technical Details
AC-3 uses a modified DCT operating on audio blocks of 512 samples. It supports 1.0 (mono) through 5.1 channel configurations. Bit allocation is controlled by a psychoacoustic model with exponent and mantissa coding.
History
Dolby Laboratories developed AC-3 in the early 1990s. It debuted in cinemas with Batman Returns (1992) and became mandatory for DVD-Video in 1997. Dolby Digital Plus (E-AC-3) is the evolution for streaming.