How does it work?

In order to stream music from an MP3 player (or other device such as a handset) to Bluetooth stereo headphones, both devices must support Bluetooth's Advanced Audio Distribution Profile or A2DP.  Before transfer, the stereo data is compressed using the Bluetooth SIG's mandatory format called Sub Band Coding or SBC.  At the other end of the wireless link, the data stream is decompressed to PCM and played via the Bluetooth device's DAC.

Standardisation on SBC is important. However, it doesn't match the formats that consumers use to store their music, which are standards such as MP3. This means that if stereo headphones support only SBC, then the music player, phone or other device has to perform 'transcoding' to decompress/recompress files before transmission (to transcode an MP3 file a player would convert MP3 to PCM and then to SBC, increasing power consumption). SBC is also not as efficient at compacting files as formats such as MP3, so a higher duty cycle is required to stream files.

CSR has exploited the architecture of its DSP-equipped BlueCore5-Multimedia device to allow MP3 files to be streamed directly from BlueCore Player to Bluetooth headphones that are implemented using BlueCore5-Multimedia.  This can result in significant power savings and better audio quality (it can stream the highest compression rate of 320 kbps direct).  Other important music CODEC formats will also be supported.

Power consumption can be reduced considerably by using BlueCore5-Multimedia for the headphone end of the link, as MP3 files (and other formats) may be streamed directly. Note: this diagram shows only 'standard' Bluetooth.  An EDR link decreases power consumption greatly.