simplehandler.py

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# Copyright (C) 2009--2013  Kipp Cannon, Chad Hanna, Drew Keppel
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.


#
# =============================================================================
#
#                                   Preamble
#
# =============================================================================
#


import sys
import os


import pygtk
pygtk.require("2.0")
import gobject
gobject.threads_init()
import pygst
pygst.require('0.10')
import gst
import signal


## @file
# The simplehander module
#
# ### Review Status
#
# | Names                                       | Hash                                        | Date       |
# | ------------------------------------------- | ------------------------------------------- | ---------- |
# | Florent, Sathya, Duncan Me., Jolien, Kipp, Chad | b3ef077fe87b597578000f140e4aa780f3a227aa    | 2014-05-01 |
#
# #### Action items
#
# - Get event based programming expert to have a look?
#

## @package python.simplehandler
# The simplehander module
#



#
# =============================================================================
#
#                               Pipeline Handler
#
# =============================================================================
#


class Handler(object):
    """!
    A simple handler that prints pipeline error messages to stderr, and
    stops the pipeline and terminates the mainloop at EOS.  Complex
    applications will need to write their own pipeline handler, but for
    most simple applications this will suffice, and it's easier than
    copy-and-pasting this all over the place.
    """
    def __init__(self, mainloop, pipeline):
        self.mainloop = mainloop
        self.pipeline = pipeline

        bus = pipeline.get_bus()
        bus.add_signal_watch()
        self.on_message_handler_id = bus.connect("message", self.on_message)

        def excepthook(*args):
            # system exception hook that forces hard exit.  without this,
            # exceptions that occur inside python code invoked as a call-back
            # from the gstreamer pipeline just stop the pipeline, they don't
            # cause gstreamer to exit.

            # FIXME:  they probably *would* cause if we could figure out why
            # element errors and the like simply stop the pipeline instead of
            # crashing it, as well.  Perhaps this should be removed when/if the
            # "element error's don't crash program" problem is fixed
            sys.__excepthook__(*args)
            os._exit(1)

        sys.excepthook = excepthook


    def quit(self, bus):
        """
        Decouple this object from the Bus object to allow the Bus'
        reference count to drop to 0, and .quit() the mainloop
        object.  This method is invoked by the default EOS and
        ERROR message handlers.
        """
        bus.disconnect(self.on_message_handler_id)
        del self.on_message_handler_id
        bus.remove_signal_watch()
        self.mainloop.quit()

    def do_on_message(self, bus, message):
        """!
        Add extra message handling by overriding this in your
        subclass.  If this method returns True, no further message
        handling is performed.  If this method returns False,
        message handling continues with default cases or EOS, INFO,
        WARNING and ERROR messages.
        """
        return False

    def on_message(self, bus, message):
        if self.do_on_message(bus, message):
            pass
        elif message.type == gst.MESSAGE_EOS:
            self.pipeline.set_state(gst.STATE_NULL)
            self.quit(bus)
        elif message.type == gst.MESSAGE_INFO:
            gerr, dbgmsg = message.parse_info()
            print >>sys.stderr, "info (%s:%d '%s'): %s" % (gerr.domain, gerr.code, gerr.message, dbgmsg)
        elif message.type == gst.MESSAGE_WARNING:
            gerr, dbgmsg = message.parse_warning()
            print >>sys.stderr, "warning (%s:%d '%s'): %s" % (gerr.domain, gerr.code, gerr.message, dbgmsg)
        elif message.type == gst.MESSAGE_ERROR:
            gerr, dbgmsg = message.parse_error()
            # FIXME:  this deadlocks.  shouldn't we be doing this?
            #self.pipeline.set_state(gst.STATE_NULL)
            self.quit(bus)
            sys.exit("error (%s:%d '%s'): %s" % (gerr.domain, gerr.code, gerr.message, dbgmsg))


class OneTimeSignalHandler(object):
    """!
    A helper class for application signal handling.  Use this to help your
    application to cleanly shutdown gstreamer pipelines when responding to e.g.,
    ctrl+c.
    """
    def __init__(self, pipeline, signals = [signal.SIGINT, signal.SIGTERM]):
        self.pipeline = pipeline
        self.count = 0
        for sig in signals:
            signal.signal(sig, self)

    def do_on_call(self, signum, frame):
        """!
        Over ride this for your subclass
        """
        pass

    def __call__(self, signum, frame):
        self.count += 1
        if self.count == 1:
            print >>sys.stderr, "*** SIG %d attempting graceful shutdown (this might take several minutes) ... ***" % signum
            try:
                self.do_on_call(signum, frame)
                if not self.pipeline.send_event(gst.event_new_eos()):
                    raise Exception("pipeline.send_event(EOS) returned failure")
            except Exception, e:
                print >>sys.stderr, "graceful shutdown failed: %s\naborting." % str(e)
                os._exit(1)
        else:
                print >>sys.stderr, "*** received SIG %d %d times... ***" % (signum, self.count)