Because of the need to send data in real time, combined with the relatively unreliable connection quality of Bluetooth, compressing audio data before sending from one device to another is a necessity. Possibly because the technology is generally used for things like mobile phones, finding a way to transmit audio losslessly hasn't apparently been a priority for most companies.
However, when music that was already encoded with some loss (like MP3 or AAC) it doesn't make much sense to re-compress it with more loss before sending it to a device like Bluetooth stereo headphones.
"The main drawback of putting MP3 or ACC Decode in [Bluetooth] headphones," Greg Burns, OINA's Chief Technology Officer, told PC Magazine, "is a business rather than a technical issue: the wireless headphone becomes burdened with the MP3 royalty. Standard royalties for devices are 75 cents, which is a significant piece of the overall BOM (bill-of-materials) cost and may be in the $20 range. If the headphones also support AAC, this can add another dollar…Since an MP3 player will already have an MP3 and/or AAC decoder built in, this means that the consumer buying the headphones is effectively paying twice for the MP3 and AAC decode capabilities."
One goal for this codec was to avoid requiring a lot of power to implement it. According to Burns actually requires about the same number of instructions as the (lossy) SBC codec, currently used for Bluetooth.
Source: PC Magazine
Written by: Rich Fiscus @ 1 Aug 2007 17:58
