A very simple gst plugin in python

print_tst.py

#!/usr/local/bin/python3
# -*- Mode: Python -*-
# vi:si:et:sw=4:sts=4:ts=4

# This is a modified version of https://github.com/GStreamer/gst-python/blob/master/examples/plugins/python/identity.py
import gi
gi.require_version("Gst", "1.0")
gi.require_version('GstBase', '1.0')

from gi.repository import Gst, GObject, GstBase
Gst.init(None)


class print_tst(GstBase.BaseTransform):
    __gstmetadata__ = ("Print test",
                       "Transform",
                       "Simple plugin to string string",
                       'Felipe Ortiz')

    __gsttemplates__ = (Gst.PadTemplate.new("src",
                                            Gst.PadDirection.SRC,
                                            Gst.PadPresence.ALWAYS,
                                            Gst.Caps.new_any()),
                        Gst.PadTemplate.new("sink",
                                            Gst.PadDirection.SINK,
                                            Gst.PadPresence.ALWAYS,
                                            Gst.Caps.new_any()))

    def __init__(self):
        GstBase.BaseTransform.__init__(self)

    # The problem: when I switch between do_transform_ip and do_transform
    # the following message appears:
    # fortiz$ gst-launch-1.0 filesrc location=/path/to/any/text/file ! print_tst ! fakesink
    # Setting pipeline to PAUSED ...
    # Pipeline is PREROLLING ...
    # (gst-launch-1.0:12864): GStreamer-CRITICAL **: gst_mini_object_unref: assertion 'mini_object != NULL' failed
    # and the command never ends...
    
    # def do_transform(self, in_buff, out_buff):
    #     err, map_info = in_buff.map(Gst.MapFlags.READ)
    #     print(map_info.data)
    #     return Gst.FlowReturn.OK

    def do_transform_ip(self, buff):
        err, map_info = buff.map(Gst.MapFlags.READ)
        print(map_info.data)
        return Gst.FlowReturn.OK


GObject.type_register(print_tst)
__gstelementfactory__ = ("print_tst", Gst.Rank.NONE, print_tst)