python: Update plugin examples

Fix warnings from bindings changes in various plugin
examples

Fix the python mixer plugin by ensuring that PIL
is not holding a reference to mapped GstBuffer memory.

Port the filesrc example from old_examples

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5187>

subprojects/gst-python/examples/plugins/python/audioplot.py

@@ -15,7 +15,6 @@ gi.require_version('Gst', '1.0')
 gi.require_version('GstBase', '1.0')
 gi.require_version('GstAudio', '1.0')
 gi.require_version('GstVideo', '1.0')
-
 from gi.repository import Gst, GLib, GObject, GstBase, GstAudio, GstVideo
 
 try:
@@ -55,7 +54,7 @@ DEFAULT_FRAMERATE_DENOM = 1
 
 
 class AudioPlotFilter(GstBase.BaseTransform):
-    __gstmetadata__ = ('AudioPlotFilter','Filter', \
+    __gstmetadata__ = ('AudioPlotFilter', 'Filter',
                        'Plot audio waveforms', 'Mathieu Duponchelle')
 
     __gsttemplates__ = (Gst.PadTemplate.new("src",
@@ -187,10 +186,8 @@ class AudioPlotFilter(GstBase.BaseTransform):
             return ret.fixate()
 
     def do_set_caps(self, icaps, ocaps):
-        in_info = GstAudio.AudioInfo()
-        in_info.from_caps(icaps)
-        out_info = GstVideo.VideoInfo()
-        out_info.from_caps(ocaps)
+        in_info = GstAudio.AudioInfo.new_from_caps(icaps)
+        out_info = GstVideo.VideoInfo().new_from_caps(ocaps)
 
         self.convert_info = GstAudio.AudioInfo()
         self.convert_info.set_format(GstAudio.AudioFormat.S32,
@@ -238,5 +235,6 @@ class AudioPlotFilter(GstBase.BaseTransform):
 
         return True
 
+
 GObject.type_register(AudioPlotFilter)
 __gstelementfactory__ = ("audioplot", Gst.Rank.NONE, AudioPlotFilter)

subprojects/gst-python/examples/plugins/python/filesrc.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python
+# -*- Mode: Python -*-
+# vi:si:et:sw=4:sts=4:ts=4
+
+# GStreamer python bindings
+# Copyright (C) 2002 David I. Lehn <dlehn@users.sourceforge.net>
+#               2004 Johan Dahlin  <johan@gnome.org>
+#
+# filesrc.py: implements a file source element completely in python
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Library General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library 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
+# Library General Public License for more details.
+#
+# You should have received a copy of the GNU Library General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+# Boston, MA 02110-1301, USA.
+import gi
+import sys
+
+gi.require_version('Gst', '1.0')
+gi.require_version('GstBase', '1.0')
+from gi.repository import GLib, Gst, GObject, GstBase
+
+
+if __name__ == '__main__':
+    Gst.init(None)
+Gst.init_python()
+
+
+class FileSource(GstBase.BaseSrc):
+    __gstmetadata__ = ('PyFileSource', 'Source',
+                       'Custom Python filesrc example', 'Jan Schmidt')
+
+    __gsttemplates__ = (
+        Gst.PadTemplate.new("src",
+                            Gst.PadDirection.SRC,
+                            Gst.PadPresence.ALWAYS,
+                            Gst.Caps.new_any()),
+    )
+
+    blocksize = 4096
+    fd = None
+
+    def __init__(self, name):
+        super().__init__()
+        self.curoffset = 0
+        self.set_name(name)
+
+    def set_property(self, name, value):
+        if name == 'location':
+            self.fd = open(value, 'rb')
+
+    def do_create(self, offset, size, wot):
+        if offset != self.curoffset:
+            self.fd.seek(offset, 0)
+        data = self.fd.read(self.blocksize)
+        if data:
+            self.curoffset += len(data)
+            return Gst.FlowReturn.OK, Gst.Buffer.new_wrapped(data)
+        else:
+            return Gst.FlowReturn.EOS, None
+
+
+GObject.type_register(FileSource)
+__gstelementfactory__ = ("filesrc_py", Gst.Rank.NONE, FileSource)
+
+
+def main(args):
+    Gst.init()
+
+    if len(args) != 3:
+        print(f'Usage: {args[0]} input output')
+        return -1
+
+    bin = Gst.Pipeline('pipeline')
+
+    filesrc = FileSource('filesource')
+    assert filesrc
+    filesrc.set_property('location', args[1])
+
+    filesink = Gst.ElementFactory.make('filesink', 'sink')
+    filesink.set_property('location', args[2])
+
+    bin.add(filesrc, filesink)
+    Gst.Element.link_many(filesrc, filesink)
+
+    bin.set_state(Gst.State.PLAYING)
+    mainloop = GLib.MainLoop()
+
+    def bus_event(bus, message):
+        t = message.type
+        if t == Gst.MessageType.EOS:
+            mainloop.quit()
+        elif t == Gst.MessageType.ERROR:
+            err, debug = message.parse_error()
+            print(f"Error: {err}, {debug}")
+            mainloop.quit()
+        return True
+    bus = bin.get_bus()
+    bus.add_signal_watch()
+    bus.connect('message', bus_event)
+
+    mainloop.run()
+    bin.set_state(Gst.State.NULL)
+
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv))

subprojects/gst-python/examples/plugins/python/mixer.py

@@ -17,7 +17,6 @@ import gi
 gi.require_version('Gst', '1.0')
 gi.require_version('GstBase', '1.0')
 gi.require_version('GObject', '2.0')
-
 from gi.repository import Gst, GObject, GstBase
 
 Gst.init_python()
@@ -41,14 +40,16 @@ OCAPS = Gst.Caps(Gst.Structure('video/x-raw',
                                height=240,
                                framerate=Gst.Fraction(30, 1)))
 
+
 class BlendData:
     def __init__(self, outimg):
         self.outimg = outimg
         self.pts = 0
         self.eos = True
 
+
 class Videomixer(GstBase.Aggregator):
-    __gstmetadata__ = ('Videomixer','Video/Mixer', \
+    __gstmetadata__ = ('Videomixer', 'Video/Mixer',
                        'Python video mixer', 'Mathieu Duponchelle')
 
     __gsttemplates__ = (
@@ -73,6 +74,10 @@ class Videomixer(GstBase.Aggregator):
         bdata.outimg = Image.blend(bdata.outimg, img, alpha=0.5)
         bdata.pts = buf.pts
 
+        # Need to ensure the PIL image has been released, or unmap will fail
+        # with an outstanding memoryview buffer error
+        del img
+
         buf.unmap(info)
 
         bdata.eos = False
@@ -100,5 +105,6 @@ class Videomixer(GstBase.Aggregator):
 
         return Gst.FlowReturn.OK
 
+
 GObject.type_register(Videomixer)
 __gstelementfactory__ = ("py_videomixer", Gst.Rank.NONE, Videomixer)