Codec

A codec is the pair of procedures that encode sound into a compact digital form and decode it again at the receiver. The name comes from coder and decoder.

Different systems use different codecs, and a receiver must support the one the broadcaster uses. DAB+ uses a variant of AAC, according to dabplus.ch. A radio without that decoder cannot play DAB+ even if it can pick up the signal.

The codec also influences how a station sounds at a given bit rate. A more efficient codec keeps more of the quality while using less data, which is how DAB+ fits more programmes into a block than the original DAB.