Bluetooth Profile – Advanced Audio Distribution Profile
Essay title: Bluetooth Profile – Advanced Audio Distribution Profile
The following profiles are defined and adopted by the Bluetooth SIG:
[edit] Advanced Audio Distribution Profile (A2DP)
This profile defines how high quality audio (stereo or mono) can be streamed from one device to another over a Bluetooth connection[1] – for example, music streamed from a mobile phone to a wireless headset.
A2DP was initially used in conjunction with an intermediate Bluetooth transceiver that connects to a standard output audio jack, encodes the incoming audio to a Bluetooth-friendly format, and sends the signal wirelessly to Bluetooth headphones that decode and play the audio. However, many Bluetooth 1.1, 1.2, and 2.0 mobile phones and portable media players natively support A2DP, and most newer Bluetooth 2.0 headphones support it as well.[2] Bluetooth headphones, especially the more advanced models, often come with a microphone and support for the Audio/Video Remote Control (AVRCP), Headset (HSP) and Handsfree (HFP) profiles.
A2DP[3] is designed to transfer a 2-channel stereo audio stream, like music from an MP3 player, to a headset or car radio. This profile relies on AVDTP and GAVDP. It includes mandatory support for low complexity Sub Band Codec (SBC) and supports optionally: MPEG-1,2 Audio, MPEG-2,4 AAC and ATRAC, and is extensible to support manufacturer-defined codecs. Most bluetooth stacks implement the SCMS-T copyright protection. In these cases it is not possible to connect the A2DP headphones for high quality audio. E.g. the Motorola HT820 can be used for high quality audio only with certain versions of the Toshiba bluetooth stack.
[edit] Operating Systems
Linux desktop distribution is still sketchy. There exists open source code Bluetooth-alsa Project that integrates with ALSA (Linux) to provide any media player that makes use of ALSA to transmit audio over A2DP.
Mac OS X v10.4, the current version of Apples Mac OS X operating system, does not include support for A2DP (there is a limited hack to circumvent this on Intel Macs [4]); however, the developer preview release of Apples forthcoming Mac OS X v10.5 does[5]
Palm OS A2DP support has been introduced in 2006 by Softick in Softick Audio Gateway shareware program.
Windows Mobile – used to be called Pocket PC – from version 5, based on Windows CE 5.0 kernel, fully supports A2DP if appropriate device is present (ie embedded in the PDA, phone etc).
Windows XP does not support A2DP out of the box, but newer Bluetooth USB dongles and built-in adapters include drivers with A2DP support. [2].
Windows Vista does not support A2DP out of the box[6], but does look for drivers for it, enabling hardware makers or third parties to provide drivers for A2DP without reworking the entire Bluetooth stack. Broadcomms version 6 bluetooth driver provides such A2DP extension for Windows Vista, for all Broadcomm bluetooth hardware.
[edit] Audio/Video Remote Control Profile (AVRCP)
This profile is designed to provide a standard interface to control TVs, Hi-fi equipment, etc. to allow a single remote control (or other device) to control all of the A/V equipment to which a user has access. It may be used in concert with A2DP or VDP.
It has the possibility for vendor-dependent extensions. The Generic Media Control Profile (GMCP) is proposed to be an open standard for transfer of media-content-related information using those extensions.
[edit] Basic Imaging Profile (BIP)
This profile is designed for sending images between devices and includes the ability to resize, and convert images to make them suitable for the receiving device. It may be broken down into smaller pieces:
Image Push
Allows the sending of images from a device the user controls.
Image Pull
Allows the browsing and retrieval of images from a remote device.
Advanced Image Printing
print images with advanced options using the DPOF format developed by Canon, Kodak, Fujifilm, and Matsushita
Automatic Archive
Allows the automatic backup of all the new images from a target device. For example, a laptop could download all of the new pictures from a camera whenever it is within range.
Remote Camera
Allows the initiator to remotely use a digital camera. For example, a user could place a camera on a tripod for a group photo, use their