Advanced Audio Distribution Profile

A2DP describes how stereo-quality audio can be streamed from a media source to a sink.
Source (SRC) - A device is the SRC when it acts as a source of a digital audio stream that is delivered to the SNK of the piconet.
Sink (SNK) - A device is the SNK when it acts as a sink of a digital audio stream delivered from the SRC on the same piconet.

A2DP defines the protocols and procedures that realize distribution of audio content of high-quality in mono or stereo on ACL channels. The term "advanced audio," therefore, should be distinguished from "Bluetoothaudio," which indicates distribution of narrow band voice on SCO channels as defined in the baseband specification.

Summary:

• A2DP includes mandatory support for low complexity subband codec (SBC) and supports optionally MPEG-1,2 Audio,
  MPEG-2,4 AAC.

• A2DP is only half-duplex

• CSR's eXtension Programme now features Enhanced apt-X. Porting APT-x audio codec on CSR BlueCore Device Multimedia, which provides significantly better audio quality then SBC.

• SDK supports FastStream audio codec which reduces A2DP latency to 40ms