monitor_audio.py

#!/usr/bin/python

# based on monitor-bluetooth
# Changes by Domen Puncer <domen@cba.si>

import gobject
import dbus
import dbus.mainloop.glib
import os, subprocess
import re


print("Starting bluetooth monitoring...")

DEVICE="alsa_output.usb-Burr-Brown_from_TI_USB_Audio_DAC-00-DAC.analog-stereo"

"""

"""
def loopback_modules():
    cmd = ["sudo", "-u", "pi", "pactl", "list", "modules", "short"]
    res = subprocess.check_output(cmd)
    # non-empty lines in result
    for line in [line.strip() for line in res.split("\n") if line.strip()]:
        groups = re.match("(?P<id>[0-9]+)\s+module-loopback\tsource=bluez_source\.(?P<mac>[\w]{17}) sink=.*", line)
        if groups:
            yield groups.group("id"), groups.group("mac")


# we want this event: {AudioSource.PropertyChanged} [/org/bluez/16797/hci0/dev_00_24_7E_51_F7_52] State = playing
# and when that happens: pactl load-module module-loopback source=bluez_source.00_24_7E_51_F7_52 sink=alsa_output.pci-0000_00_1b.0.analog-stereo
def property_changed(name, value, path, interface):
    iface = interface[interface.rfind(".") + 1:]
    val = str(value)
    print("{{{}.PropertyChanged}} [{}] {} = {}".format(iface, path, name, val))

    # continue and add new module
    bt_addr = "_".join(path.split('/')[-1].split('_')[1:])

    if iface == "AudioSource" and name == "State" and val == "playing":
        # check if there already is a module for this mac:
        if bt_addr in [mac for pos, mac in loopback_modules()]:
            print("Loopback module already loaded for {}.".format(bt_addr))
            return

        # build command, run as user pi
        cmd = ["sudo", "-u", "pi",
            "pactl", "load-module", "module-loopback",
            "source=bluez_source.{}".format(bt_addr), "sink={}".format(DEVICE)]
        module_nr = subprocess.check_output(cmd)
        print("Loaded loopback for {} with module #{}.".format(bt_addr, module_nr))

    elif iface == "AudioSource" and name == "State" and val == "disconnected":
        # disconnection, find index, unload-module
        for (pos, mac) in loopback_modules():
            if mac == bt_addr:
                res = subprocess.check_output(["sudo", "-u", "pi", "pactl", "unload-module", pos])
                print("Cleaned index {}, result: {}.".format(pos, res))


def object_signal(value, path, interface, member):
    iface = interface[interface.rfind(".") + 1:]
    val = str(value)
    print("{{}.{}} [{}] Path = {}".format(iface, member, path, val))

if __name__ == '__main__':
    dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)

    bus = dbus.SystemBus()

    bus.add_signal_receiver(property_changed, bus_name="org.bluez", signal_name = "PropertyChanged", path_keyword="path", interface_keyword="interface")

    mainloop = gobject.MainLoop()
    mainloop.run()