support: add support for other clocks

Add support for using other clocks.
clock.id can be used to set one of the system clocks.
clock.device can be used to open a clock device such as a PTP clock
device.
Use a dll to track the progress of non-monotonic clocks.

src/daemon/pipewire.conf.in

@@ -194,6 +194,8 @@ context.objects = [
             node.name       = Dummy-Driver
             node.group      = pipewire.dummy
             priority.driver = 20000
+            #clock.id       = monotonic # realtime | tai | monotonic-raw | boottime
+            #clock.name     = "clock.system.monotonic"
         }
     }
     { factory = spa-node-factory
@@ -205,6 +207,20 @@ context.objects = [
             node.freewheel  = true
         }
     }
+    # An example clock reading from /dev/ptp0. Another option is to sync the
+    # ptp clock to CLOCK_TAI and then set clock.id = tai.
+    #{ factory = spa-node-factory
+    #    args = {
+    #        factory.name    = support.node.driver
+    #        node.name       = PTP0-Driver
+    #        node.group      = pipewire.ptp0
+    #        priority.driver = 30000
+    #        clock.name      = "clock.system.ptp0"
+    #        #clock.id       = tai
+    #        clock.device    = "/dev/ptp0"
+    #    }
+    #}
+
     # This creates a new Source node. It will have input ports
     # that you can link, to provide audio for this source.
     #{ factory = adapter