BLUETOOTH SPECIFICATION Page 15 of 75
Advanced Audio Distribution Profile (A2DP)
Bluetooth SIG Proprietary
3 Application Layer
This section describes the feature requirements on units complying with the A2DP.
Table 3.1 shows the feature requirements for this profile.
Table 3.1: Application Layer Features
Table 3.2 maps each feature to the procedures used for that feature, and shows
whether the procedure is optional, mandatory, or conditional. The procedures are
described in the reference section.
Table 3.2: Application Layer Feature to Procedure Mapping
3.1 Audio Streaming Set Up
If the AVDTP version of the remote device is unknown, the device shall perform a SDP
query to get the AVDTP version on the remote device. This shall be performed before
the GAVDP_ConnectionEstablishment procedure is performed. This is required since
some commands in the audio streaming setup procedure depend on the AVDTP
version.
When a device wishes to start streaming of audio content, the device firstly needs to set
up a streaming connection. Signaling procedures and typical signaling flows are
illustrated in Section 4.1 and Appendix A of GAVDP [3], respectively. During such set up
procedure, the devices select the most suitable audio streaming parameters. There are
two kinds of services configured; one is an application service capability, and the other
is a transport service capability. (For details, see section 4.4 in AVDTP [4].) This profile
specifies audio-specific parameters necessary for these signaling procedures. An
example of how the session signaling is performed is described in Chapter 14 of
GAVDP [3] and in Chapter 13 of this specification.
The application service capability for A2DP consists of audio codec capability and
content protection capability. Requirements for audio codec interoperability and details
of codec parameters such as mode, sampling frequency, and bit rate are described in
Chapter 4. The content protection capability is described in Appendix A as informative.
The transport service capability is provided by AVDTP in order to manipulate the
streaming packets more intelligently. Appropriate configuration of these services
increases channel throughput. Available services are listed in Section 5.1.2.
3.2 Audio Streaming
Once streaming connection is established and Start Streaming procedure in GAVDP is
executed, both SRC and SNK are in the STREAMING state, in which the SRC (SNK) is
ready to send (receive) audio stream. (See section 4.1 in GAVDP [3].) The SRC uses
