1 files changed, 116 insertions, 0 deletions
diff --git a/voctocore/lib/shmsrc.py b/voctocore/lib/shmsrc.py
new file mode 100644
index 0000000..53a7d9d
--- /dev/null
+++ b/voctocore/lib/shmsrc.py
@@ -0,0 +1,116 @@
+#!/usr/bin/python3
+import time, logging
+from gi.repository import GLib, Gst
+
+from lib.config import Config
+
+class FailsafeShmSrc(Gst.Bin):
+	log = logging.getLogger('FailsafeShmSrc')
+	last_buffer_arrived = 0
+	is_in_failstate = True
+
+	def __init__(self, name, socket):
+		super().__init__()
+		self.set_name(socket)
+
+		caps = Gst.Caps.from_string(Config.get('sources', 'videocaps'))
+		self.log.debug('parsing videocaps from config: %s', caps.to_string())
+
+		# Create elements
+		self.shmsrc = Gst.ElementFactory.make('shmsrc', None)
+		self.identity1 = Gst.ElementFactory.make('identity', None)
+		self.identity2 = Gst.ElementFactory.make('identity', None)
+		self.switch = Gst.ElementFactory.make('input-selector', None)
+		self.failsrc = Gst.ElementFactory.make('videotestsrc', None)
+
+		if not self.shmsrc or not self.identity1 or not self.identity2 or not self.switch or not self.failsrc:
+			self.log.error('could not create elements')
+
+		# Add elements to Bin
+		self.add(self.shmsrc)
+		self.add(self.identity1)
+		self.add(self.identity2)
+		self.add(self.switch)
+		self.add(self.failsrc)
+
+		# Get Switcher-Pads
+		self.goodpad = self.switch.get_request_pad('sink_%u')
+		self.failpad = self.switch.get_request_pad('sink_%u')
+
+		# Set properties
+		self.shmsrc.set_property('socket-path', socket)
+		self.shmsrc.set_property('is-live', True)
+		self.shmsrc.set_property('do-timestamp', True)
+		self.identity2.set_property('sync', True)
+		self.switch.set_property('active-pad', self.failpad)
+
+		# Link elements
+		self.shmsrc.link_filtered(self.identity1, caps)
+		self.identity1.get_static_pad('src').link(self.goodpad)
+
+		self.failsrc.link_filtered(self.identity2, caps)
+		self.identity2.get_static_pad('src').link(self.failpad)
+
+		# Install pad probes
+		self.shmsrc.get_static_pad('src').add_probe(Gst.PadProbeType.BLOCK | Gst.PadProbeType.EVENT_DOWNSTREAM, self.event_probe, None)
+		self.shmsrc.get_static_pad('src').add_probe(Gst.PadProbeType.BLOCK | Gst.PadProbeType.BUFFER, self.data_probe, None)
+
+		# Install Watchdog
+		GLib.timeout_add(500, self.watchdog)
+
+		# Add Ghost Pads
+		self.add_pad(
+			Gst.GhostPad.new('src', self.switch.get_static_pad('src'))
+		)
+
+	def do_handle_message(self, msg):
+		if msg.type == Gst.MessageType.ERROR and msg.src == self.shmsrc:
+			self.log.warning('received error-message from ShmSrc, dropping')
+		else:
+			Gst.Bin.do_handle_message(self, msg)
+
+	def event_probe(self, pad, info, ud):
+		e = info.get_event()
+		if e.type == Gst.EventType.EOS:
+			self.log.warning('received EOS-event on event-probe, dropping')
+			self.switch_to_failstate()
+			return Gst.PadProbeReturn.DROP
+		
+		return Gst.PadProbeReturn.PASS
+
+
+	def data_probe(self, pad, info, ud):
+		self.last_buffer_arrived = time.time()
+		self.switch_to_goodstate()
+		return Gst.PadProbeReturn.PASS
+
+	def watchdog(self):
+		if self.last_buffer_arrived + 0.1 < time.time():
+			self.log.warning('watchdog encountered a timeout')
+			self.switch_to_failstate()
+		
+		if self.last_buffer_arrived + 3 < time.time() and round(time.time() % 3) == 0:
+			self.restart()
+		
+		return True
+	
+	def restart(self):
+		self.log.warning('restarting ShmSrc')
+		self.shmsrc.set_state(Gst.State.NULL)
+		self.shmsrc.set_state(Gst.State.PLAYING)
+	
+	def switch_to_goodstate(self):
+		if not self.is_in_failstate:
+			return
+		
+		self.log.warning('switching output to goodstate')
+		self.is_in_failstate = False
+		self.switch.set_property('active-pad', self.goodpad)
+	
+	def switch_to_failstate(self):
+		if self.is_in_failstate:
+			return
+		
+		self.log.warning('switching output to failstate')
+		self.is_in_failstate = True
+		self.switch.set_property('active-pad', self.failpad)