Bluetooh Audio Through the NSLU2.

@POTUSCamacho has an interesting article about how to use the NSLU2 in combination with a USB bluetooth adapter as an audio server. POTUSCamacho explains how to do it with a mono audio adapter but clarifies that it should be possible to do it using a stereo adapter.

Lets take a look at this interesting howto:

Once you have installed Ubuntu, log in and update your packages:

sudo -i apt-get update

Then install the following packages:

sudo -i apt-get install linux-sound-base bluetooth bluez bluez-alsa bluez-btsco bluez-compat bluez-utils python python-bluez vlc

Note: I do alot of other development stuff on my unit. I may have left off something, and if so let me know if you try it and it doesn't work.
Now that the needed packages are installed, an .asoundrc needs to be created in your user home directory. An example:

pcm.bluetooth { type bluetooth device 00:00:00:00:00:00 }

Edit the device section with the MAC address of your bluetooth headset. To find this, issue a reset of the bluetooth adapter by issuing the command:

hciconfig hci0 reset

Then place your headset in pairing mode and issue the following command:

sdptool browse

Now copy the following python script into a file named pair.py:

#!/usr/bin/python import gobject import sys import dbus import dbus.service import dbus.mainloop.glib class Rejected(dbus.DBusException): _dbus_error_name = "org.bluez.Error.Rejected" class Agent(dbus.service.Object): exit_on_release = True def set_exit_on_release(self, exit_on_release): self.exit_on_release = exit_on_release @dbus.service.method("org.bluez.Agent", in_signature="", out_signature="") def Release(self): print "Release" if self.exit_on_release: mainloop.quit() @dbus.service.method("org.bluez.Agent", in_signature="os", out_signature="") def Authorize(self, device, uuid): print "Authorize (%s, %s)" % (device, uuid) authorize = raw_input("Authorize connection (yes/no): ") if (authorize == "yes"): return raise Rejected("Connection rejected by user") @dbus.service.method("org.bluez.Agent", in_signature="o", out_signature="s") def RequestPinCode(self, device): print "RequestPinCode (%s)" % (device) return raw_input("Enter PIN Code: ") @dbus.service.method("org.bluez.Agent", in_signature="o", out_signature="u") def RequestPasskey(self, device): print "RequestPasskey (%s)" % (device) passkey = raw_input("Enter passkey: ") return dbus.UInt32(passkey) @dbus.service.method("org.bluez.Agent", in_signature="ou", out_signature="") def DisplayPasskey(self, device, passkey): print "DisplayPasskey (%s, %d)" % (device, passkey) @dbus.service.method("org.bluez.Agent", in_signature="ou", out_signature="") def RequestConfirmation(self, device, passkey): print "RequestConfirmation (%s, %d)" % (device, passkey) confirm = raw_input("Confirm passkey (yes/no): ") if (confirm == "yes"): return raise Rejected("Passkey doesn't match") @dbus.service.method("org.bluez.Agent", in_signature="s", out_signature="") def ConfirmModeChange(self, mode): print "ConfirmModeChange (%s)" % (mode) @dbus.service.method("org.bluez.Agent", in_signature="", out_signature="") def Cancel(self): print "Cancel" def create_device_reply(device): print "New device (%s)" % (device) mainloop.quit() def create_device_error(error): print "Creating device failed: %s" % (error) mainloop.quit() if __name__ == '__main__': dbus.mainloop.glib.DBusGMainLoop(set_as_default=True) bus = dbus.SystemBus() manager = dbus.Interface(bus.get_object("org.bluez", "/"), "org.bluez.Manager") if len(sys.argv) > 1: path = manager.FindAdapter(sys.argv[1]) else: path = manager.DefaultAdapter() adapter = dbus.Interface(bus.get_object("org.bluez", path), "org.bluez.Adapter") path = "/test/agent" agent = Agent(bus, path) mainloop = gobject.MainLoop() if len(sys.argv) > 2: if len(sys.argv) > 3: device = adapter.FindDevice(sys.argv[2]) adapter.RemoveDevice(device) agent.set_exit_on_release(False) adapter.CreatePairedDevice(sys.argv[2], path, "DisplayYesNo", reply_handler=create_device_reply, error_handler=create_device_error) else: adapter.RegisterAgent(path, "DisplayYesNo") print "Agent registered" mainloop.run() #adapter.UnregisterAgent(path) #print "Agent unregistered"

Now place your headset into pairing mode again and issue the follow command:

sudo -i python pair.py hci0 00:00:00:00:00:00

Once again replacing the address above with your headsets MAC. The last step involves editing the vlcrc. To do this, issue the command:

pico .vlc/vlcrc

Scroll down and replace:

alsadev=(default soundcard)

To:

alsadev=bluetooth

If it does not exist then create it.

Now you should be ready to listen to audio. To listen to the audio from NASA TV's online video stream, issue the command:

cvlc --aout-rate 8000 --novideo http://www.nasa.gov/55644main_NASATV_Windows.asx

If everything is working you should hear audio. Keep in mind that the sample rate needs to be 8000Hz since that is the sample rate the headset can handle.

To pair another headset, or to re-pair the current, the /var/lib/bluetooth/(your MAC)/linkkeys file must be deleted. It will regenerate once you have paired the devices. Also remember that the .asoundrc file must be edited to match a different headset as the MAC will be different.

To find out more info about this article, please visit POTUSCamacho Industries blog.

Spanish version: Audio vía bluetooh desde el NSLU2.