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SBC (codec)
The Low Complexity Subband Coding or (SBC), is an audio subband codec specified by the Bluetooth Special Interest Group (SIG) for the Advanced Audio Distribution Profile (A2DP).〔Bluetooth SIG, Specification of the Bluetooth System, Profiles, Advanced Audio Distribution Profile version 1.3. https://www.bluetooth.org/docman/handlers/DownloadDoc.ashx?doc_id=260859&vId=290074〕 SBC is a digital audio encoder and decoder used to transfer data to Bluetooth audio output devices like headphones or loudspeakers. It can be also used on the Internet.〔C. Hoene, F. de Bont, "RTP Payload Format for Bluetooth's SBC audio codec", IETF draft, work in progress, Dec. 2009, http://tools.ietf.org/html/draft-hoene-avt-rtp-sbc-05〕 It was designed to obtain a reasonably good audio quality at medium bit rates while keeping low computational complexity, having Bluetooth bandwidth limitations and processing power in mind.〔〔
〕 As of A2DP version 1.3, the Low Complexity Subband Coding remains the default codec and its implementation is mandatory for devices supporting that profile. Other codecs can be run on top of A2DP along with SBC though.〔
==Design==
SBC supports mono and stereo streams, certain sampling frequencies up to 48 kHz and maximum bit rates of 198 kbit/s for mono and 345 kbit/s for stereo streams. It uses 4 or 8 subbands, an adaptive bit allocation algorithm in combination with an adaptive block PCM quantizers.〔 Frans de Bont has based the SBC audio codec on his earlier work,〔F. de Bont, M. Groenewegen and W. Oomen, "A High Quality Audio-Coding System at 128 kb/s", 98th AES Convention, Febr. 25-28, 1995.〕 and – in parts – on the MPEG-1 Audio Layer II standard. In addition, the SBC is based on the algorithms described in the EP-0400755B1.〔J.B. Rault, Y.F. Dehery, J.Y. Roudaut, A.A.M. Bruekers, R.N.J. Veldhuis, "Digital transmission system using subband coding of a digital signal", Publication number: EP0400755 (B1), Priority number(s): EP19900201369 19900530; EP19890201408 19890602〕 The patent owners wrote that they allow the free usage of SBC in Bluetooth application, with the view to boost the use of this technology.
All applications outside Bluetooth are, however, not free. The patent expired June 2, 2010.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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