path: root/voctocore/lib/shmsrc.py

#!/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, socket):
        super().__init__()

        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)