Gstreamer seamless loop test

gstseamlessloop.py

#/usr/bin/env python3
#
# Seamless loop test
# Copyright (c) 2015 Arnaud Loonstra <[email protected]>
#
# This 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 3 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, see <http://www.gnu.org/licenses/>.
#
# There's a bug in gstreamer-vaapi <0.5.10 see: https://bugzilla.gnome.org/show_bug.cgi?id=743035
# workaround is export LIBVA_DRIVER_NAME=bla to make vaapi fail en revert to software decoding
#
# test video: 
# https://github.com/raspberrypi/firmware/raw/master/opt/vc/src/hello_pi/hello_video/test.h264

import gi
gi.require_version('Gst', '1.0')
from gi.repository import GObject, Gst
print(Gst.version())

import argparse
import sys
import os

def bus_call(bus, msg, *args):
    """
    handling messages on the gstreamer bus
    """
    global prerolled, playbin, loop

    if msg.type == Gst.MessageType.ASYNC_DONE:
        if not prerolled:
            print("Initial seek ...");
            flags = Gst.SeekFlags.FLUSH | Gst.SeekFlags.SEGMENT
            playbin.seek_simple (Gst.Format.TIME, flags, 0);
            prerolled = True
    elif msg.type == Gst.MessageType.SEGMENT_DONE:
        print("Looping...")
        flags = Gst.SeekFlags.SEGMENT
        playbin.seek_simple (Gst.Format.TIME, flags, 0);
    elif msg.type == Gst.MessageType.ERROR:
        print(msg.parse_error())
        loop.quit()            # quit.... (better restart app?)
    return True

parser = argparse.ArgumentParser(description='Loop a videofile seamlessly.')
parser.add_argument('file', type=str, help='file to play')
args = parser.parse_args()
if not os.path.isfile(args.file):
    print("File {0} doesn't exist".format(file))
    sys.exit(1)

GObject.threads_init()
loop = GObject.MainLoop()
Gst.init(None)

# create playbin pipeline
prerolled = False
playbin = Gst.ElementFactory.make('playbin', 'playbin0')
bus = playbin.get_bus()
bus.add_watch(0, bus_call, loop) # 0 == GLib.PRIORITY_DEFAULT 
        
# set properties of elements
playbin.set_property("uri", "file://{0}".format(os.path.abspath(args.file)))
playbin.set_state(Gst.State.PLAYING)

try:
    loop.run()
except Exception as e:
    print(e)
finally:
    playbin.set_state(Gst.State.NULL)

To get it to work, I had to make two changes:

Problem: raise NotInitialized("Please call Gst.init(argv) before using GStreamer")
Solution: Comment out line 28.

Problem: GLib.Error('Could not open resource for reading.', 'gst-resource-error-quark', 5)
Solution: Add an extra forward slash after file:// on line 73.