Thursday, February 23, 2006
Bluetake's i-PHONO mini Bluetooth Headphone Kit Reviewed
Posted by Darius Wey in "HARDWARE" @ 09:00 AM
An Introduction to A2DP, AVRCP, HSP, and HFP
A lot of today's consumer electronics are equipped with Bluetooth, and on top of the core specification is a set of defined profiles which determine a particular usage model. These profiles are defined within a stack (or a set of drivers). A2DP, AVRCP, HSP, and HFP are four profiles which fit in the context of this review. The following is an overview of each of the four profiles, which can also be found here in its entirety:
Advanced Audio Distribution Profile (A2DP)
"A2DP describes how stereo quality audio can be streamed from a media source to a sink. The profile defines two roles of an audio source and sink. A typical usage scenario can be considered as the "walkman" class of media player. The audio source would be the music player and the audio sink is the wireless headset. 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."
Audio/Video Remote Control Profile (AVRCP)
"AVRCP is designed to provide a standard interface to control TVs, hi-fi equipment, or other to allow a single remote control (or other device) to control all the A/V equipment that a user has access to. It may be used in concert with A2DP or VDP. AVRCP defines how to control characteristics of streaming media. This includes pausing, stopping and starting playback and volume control as well as other types of remote control operations. The AVRCP defines two roles, that of a controller and target device. The controller is typically considered the remote control device while the target device is the one whose characteristics are being altered. In a "walkman" type media player scenario, the control device may be a headset that allows tracks to be skipped and the target device would be the actual medial player. This protocol specifies the scope of the AV/C Digital Interface Command Set (AV/C command set, defined by the 1394 trade association) to be applied, realizing simple implementation and easy operability. This protocol adopts the AV/C device model and command format for control messages and those messages are transported by the Audio/Video Control Transport Protocol (AVCTP). In AVRCP, the controller translates the detected user action to the A/V control signal, and then transmits it to a remote Bluetooth enabled device. The functions available for a conventional infrared remote controller can be realized in this protocol. The remote control described in this protocol is designed specifically for A/V control only."
Hands-Free Profile (HFP)
"HFP describes how a gateway device can be used to place and receive calls for a hand-free device. A typical configuration is an automobile using a mobile phone for a gateway device. In the car, the stereo is used for the phone audio and a microphone is installed in the car for sending outgoing audio. HFP is also used for a personal computer to act as a speaker phone for a mobile phone in a home or office environment. HFP uses SCO to carry a mono, PCM audio channel."
Headset Profile (HSP)
"The HSP describes how a Bluetooth enabled headset should communicate with a computer or other Bluetooth enabled device such as a mobile phone. When connected and configured, the headset can act as the remote device's audio input and output interface. The HSP relies on SCO for audio and a subset of AT commands from GSM 07.07 for minimal controls including the ability to ring, answer a call, hang up and adjust the volume."
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