AC-3 is an audio coding format commonly associated with Dolby Digital. It can carry different channel arrangements, including surround configurations. A device may decode it internally or, in supported setups, pass the encoded audio onward to another device. The source, player, television and sound equipment must support the arrangement actually being used.
A practical example
A player can send a compatible encoded AC-3 track to an AV receiver for decoding, while another setup converts audio for television speakers. Those are different output paths and can behave differently even when both receive the same programme stream.
A common misunderstanding
A Dolby Digital label does not establish that every programme contains surround sound. The actual track, selected output and receiving equipment determine the arrangement that reaches the speakers.
Related terms
Stable technical definition. Editorial approach