The
ubt driver provides support for USB Bluetooth dongles to the Bluetooth protocol stack.
USB Bluetooth dongles provide two interfaces, both of which the
ubt driver claims. The second interface is used for Isochronous data and will have several alternate configurations regarding bandwidth consumption, which can be set using the hw.ubtN.config
sysctl(8) variable. The number of alternate configurations is indicated by the value in the hw.ubtN.alt_config variable, and the isoc frame size for the current configuration is shown in the hw.ubtN.sco_rxsize and hw.ubtN.sco_txsize variables.
By default, configuration 0 is selected, which means that no bandwidth is used on the Isochronous interface and no SCO data can be sent. Consult the Bluetooth USB specification at https://www.bluetooth.org/ for complete instructions on setting bandwidth consumption. The following extract may be useful as a general guidance though details may differ between manufacturers.
0
No active voice channels
1
One voice channel with 8-bit encoding
2
Two voice channels with 8-bit encoding, or one voice channel with 16-bit encoding.
3
Three voice channels with 8-bit encoding
4
Two voice channels with 16-bit encoding
5
Three voice channels with 16-bit encoding