https://developer.bluetooth.org/TechnologyOverview/Pages/A2DP.aspx
Advanced Audio Distribution Profile (A2DP)
A2DP describes how stereo-quality audio can be streamed from a media source to a sink.
Usage Scenarios
Put simply, this is a Bluetooth enabled music player (i.e. MP3 player, walkman, stereo, etc.). The audio source is the music player and the audio sink is the wireless headset or wireless stereo speakers.
Example Products
Here are a few examples of the types of devices that use the A2DP profile:
- Stereo Headphones
- Stereo Speakers
- MP3 Players
- Music Phones
- Stereo Adapters
Getting Technical
The profile defines two roles of an audio device: source and 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 "Bluetooth audio," which indicates distribution of narrow band voice on SCO channels as defined in the baseband specification.
This profile relies on GAVDP. It includes mandatory support for low complexity subband codec (SBC) and supports optionally MPEG-1,2 Audio, MPEG-2,4 AAC and ATRAC.
The audio data is compressed in a proper format for efficient use of the limited bandwidth. Surround sound distribution is not included in the scope of this profile.
The Baseband, LMP, L2CAP and SDP are Bluetooth protocols defined in the Bluetooth Core specifications. AVDTP consists of a signaling entity for negotiation of streaming parameters and a transport entity that handles streaming itself (refer to "Profile Stack: Profile Model").
The Application layer is the entity in which the device defines application services and transport service parameters. It also adapts the audio streaming data into the defined packet format, or vice versa.
Want to know more? Read: Implementing the Advanced Audio Distribution Profile.
For even greater detail, access this in-depth PDF: Advanced Audio Distribution Profile Specification.
