Bluetooth profile#Advanced Audio Distribution Profile .28A2DP.29

A2DP (Advanced Audio Distribution Profile ) is a vendor-independent technology that allows you to send stereo audio signals wirelessly via Bluetooth to a corresponding receiver. A distinction is made between:

• Sources ( A2DP SRC: Advanced Audio Distribution Source) and
• Sinks ( A2DP - SNK: Advanced Audio Distribution Sink ).

A source can be for example a Bluetooth mobile phone, sends the audio signals to a Bluetooth headset or a car radio (receiver).

This allowed the transmission format of the audio files is defined in the A2DP specification. Essential defined A2DP called SBC codec for transmitting the audio data. MP3 is an optional codec supported, as well as AAC. Transport devices for this reason, the data in the SBC usually format.

Frequently, this profile is used in conjunction with AVRCP, to remotely control the source can.

Support by Operating Systems

• The A2DP protocol is not supported by Windows 7 on-board tools. The market, however, various Bluetooth stacks with A2DP support from various vendors are available.

• Linux supports the standard on BlueZ in conjunction with ALSA or PulseAudio.

• On the Mac, the A2DP Agent since 26 October 2007 on MacOS X 10.5 (Leopard ) is available.

• Android supports A2DP since version 1.5.

• IPhone and iPad support from operating system version iOS 3.0 A2DP.

• Windows Phone 7 also supports Advanced Audio Distribution Profile A2DP AVRCP 1.2 1.3.

• Similarly Nokia support in many of his devices with the company's own Symbian operating system to connect A2DP standard.

Quality of the audio transmission

A2DP sources must only support lossy SBC encoding, which can be used royalty-free according to standard. Therefore, many equipment manufacturers shy away from the extra support of MP3 or AAC format, since they would have to pay royalty payment. As a direct consequence, the usually stored on the sending device in compressed form music the user must first be decompressed and then again with the SBC algorithm lossy compressed for Bluetooth transmission. This can bring in theory a loss in sound quality with it. The possible bit rate of the SBC encoding is up to 345 kbit / s is very high, so that the loss in devices that use this also, is no longer in the audible range.

The first A2DP -enabled mobile phone Nokia 8800 supports direct MP3 streaming.