text: #!/usr/bin/env python3
  
  ################################################################################
  # Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
  #
  # Permission is hereby granted, free of charge, to any person obtaining a
  # copy of this software and associated documentation files (the "Software"),
  # to deal in the Software without restriction, including without limitation
  # the rights to use, copy, modify, merge, publish, distribute, sublicense,
  # and/or sell copies of the Software, and to permit persons to whom the
  # Software is furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  # THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  # DEALINGS IN THE SOFTWARE.
  ################################################################################
  
  import sys
  sys.path.append('../')
  import gi
  gi.require_version('Gst', '1.0')
  from gi.repository import GObject, Gst
  from common.is_aarch_64 import is_aarch64
  from common.bus_call import bus_call
  
  import pyds
  #from bindings.jetson import pyds
  
  PGIE_CLASS_ID_VEHICLE = 0
  PGIE_CLASS_ID_BICYCLE = 1
  PGIE_CLASS_ID_PERSON = 2
  PGIE_CLASS_ID_ROADSIGN = 3
  
  
  def osd_sink_pad_buffer_probe(pad,info,u_data):
      frame_number=0
      #Intiallizing object counter with 0.
      obj_counter = {
          PGIE_CLASS_ID_VEHICLE:0,
          PGIE_CLASS_ID_PERSON:0,
          PGIE_CLASS_ID_BICYCLE:0,
          PGIE_CLASS_ID_ROADSIGN:0
      }
      num_rects=0
  
      gst_buffer = info.get_buffer()
      if not gst_buffer:
          print("Unable to get GstBuffer ")
          return
  
      # Retrieve batch metadata from the gst_buffer
      # Note that pyds.gst_buffer_get_nvds_batch_meta() expects the
      # C address of gst_buffer as input, which is obtained with hash(gst_buffer)
      batch_meta = pyds.gst_buffer_get_nvds_batch_meta(hash(gst_buffer))
      l_frame = batch_meta.frame_meta_list
      while l_frame is not None:
          try:
              # Note that l_frame.data needs a cast to pyds.NvDsFrameMeta
              # The casting is done by pyds.NvDsFrameMeta.cast()
              # The casting also keeps ownership of the underlying memory
              # in the C code, so the Python garbage collector will leave
              # it alone.
             frame_meta = pyds.NvDsFrameMeta.cast(l_frame.data)
          except StopIteration:
              break
  
          frame_number=frame_meta.frame_num
          num_rects = frame_meta.num_obj_meta
          l_obj=frame_meta.obj_meta_list
          while l_obj is not None:
              try:
                  # Casting l_obj.data to pyds.NvDsObjectMeta
                  obj_meta=pyds.NvDsObjectMeta.cast(l_obj.data)
              except StopIteration:
                  break
              obj_counter[obj_meta.class_id] += 1
              try: 
                  l_obj=l_obj.next
              except StopIteration:
                  break
  
          # Acquiring a display meta object. The memory ownership remains in
          # the C code so downstream plugins can still access it. Otherwise
          # the garbage collector will claim it when this probe function exits.
          display_meta=pyds.nvds_acquire_display_meta_from_pool(batch_meta)
          display_meta.num_labels = 1
          py_nvosd_text_params = display_meta.text_params[0]
          # Setting display text to be shown on screen
          # Note that the pyds module allocates a buffer for the string, and the
          # memory will not be claimed by the garbage collector.
          # Reading the display_text field here will return the C address of the
          # allocated string. Use pyds.get_string() to get the string content.
          py_nvosd_text_params.display_text = "Frame Number={} Number of Objects={} Vehicle_count={} Person_count={}".format(frame_number, num_rects, obj_counter[PGIE_CLASS_ID_VEHICLE], obj_counter[PGIE_CLASS_ID_PERSON])
  
          # Now set the offsets where the string should appear
          py_nvosd_text_params.x_offset = 10
          py_nvosd_text_params.y_offset = 12
  
          # Font , font-color and font-size
          py_nvosd_text_params.font_params.font_name = "Serif"
          py_nvosd_text_params.font_params.font_size = 10
          # set(red, green, blue, alpha); set to White
          py_nvosd_text_params.font_params.font_color.set(1.0, 1.0, 1.0, 1.0)
  
          # Text background color
          py_nvosd_text_params.set_bg_clr = 1
          # set(red, green, blue, alpha); set to Black
          py_nvosd_text_params.text_bg_clr.set(0.0, 0.0, 0.0, 1.0)
          # Using pyds.get_string() to get display_text as string
          print(pyds.get_string(py_nvosd_text_params.display_text))
          pyds.nvds_add_display_meta_to_frame(frame_meta, display_meta)
          try:
              l_frame=l_frame.next
          except StopIteration:
              break
  			
      return Gst.PadProbeReturn.OK	
  
  
  def main(args):
      # Check input arguments
      if len(args) < 2:
          sys.stderr.write("usage: %s <v4l2-device-path>\n" % args[0])
          sys.exit(1)
  
      # TODO: use parsing
      width = int(args[3])
      height = int(args[5])
      
  
      # Standard GStreamer initialization
      GObject.threads_init()
      Gst.init(None)
  
      # Create gstreamer elements
      # Create Pipeline element that will form a connection of other elements
      print("Creating Pipeline \n ")
      pipeline = Gst.Pipeline()
  
      if not pipeline:
          sys.stderr.write(" Unable to create Pipeline \n")
  
      # Source element for reading from the file
      print("Creating Source \n ")
      source = Gst.ElementFactory.make("v4l2src", "usb-cam-source")
      if not source:
          sys.stderr.write(" Unable to create Source \n")
  
      caps_v4l2src = Gst.ElementFactory.make("capsfilter", "v4l2src_caps")
      if not caps_v4l2src:
          sys.stderr.write(" Unable to create v4l2src capsfilter \n")
  
  
      print("Creating Video Converter \n")
  
      # Adding videoconvert -> nvvideoconvert as not all
      # raw formats are supported by nvvideoconvert;
      # Say YUYV is unsupported - which is the common
      # raw format for many logi usb cams
      # In case we have a camera with raw format supported in
      # nvvideoconvert, GStreamer plugins' capability negotiation
      # shall be intelligent enough to reduce compute by
      # videoconvert doing passthrough (TODO we need to confirm this)
  
  
      # videoconvert to make sure a superset of raw formats are supported
      vidconvsrc = Gst.ElementFactory.make("videoconvert", "convertor_src1")
      if not vidconvsrc:
          sys.stderr.write(" Unable to create videoconvert \n")
  
      # nvvideoconvert to convert incoming raw buffers to NVMM Mem (NvBufSurface API)
      nvvidconvsrc = Gst.ElementFactory.make("nvvideoconvert", "convertor_src2")
      if not nvvidconvsrc:
          sys.stderr.write(" Unable to create Nvvideoconvert \n")
  
      caps_vidconvsrc = Gst.ElementFactory.make("capsfilter", "nvmm_caps")
      if not caps_vidconvsrc:
          sys.stderr.write(" Unable to create capsfilter \n")
  
      # Create nvstreammux instance to form batches from one or more sources.
      streammux = Gst.ElementFactory.make("nvstreammux", "Stream-muxer")
      if not streammux:
          sys.stderr.write(" Unable to create NvStreamMux \n")
  
      # Use nvinfer to run inferencing on camera's output,
      # behaviour of inferencing is set through config file
      pgie = Gst.ElementFactory.make("nvinfer", "primary-inference")
      if not pgie:
          sys.stderr.write(" Unable to create pgie \n")
  
      # Use convertor to convert from NV12 to RGBA as required by nvosd
      nvvidconv = Gst.ElementFactory.make("nvvideoconvert", "convertor")
      if not nvvidconv:
          sys.stderr.write(" Unable to create nvvidconv \n")
  
      # Create OSD to draw on the converted RGBA buffer
      nvosd = Gst.ElementFactory.make("nvdsosd", "onscreendisplay")
  
      if not nvosd:
          sys.stderr.write(" Unable to create nvosd \n")
  
      # Finally render the osd output
      if is_aarch64():
          transform = Gst.ElementFactory.make("nvegltransform", "nvegl-transform")
  
      print("Creating EGLSink \n")
      sink = Gst.ElementFactory.make("nveglglessink", "nvvideo-renderer")
      if not sink:
          sys.stderr.write(" Unable to create egl sink \n")
  
      print("Playing cam %s " %args[1])
      caps_v4l2src.set_property('caps', Gst.Caps.from_string("video/x-raw, framerate=30/1"))
      caps_vidconvsrc.set_property('caps', Gst.Caps.from_string("video/x-raw(memory:NVMM)"))
      source.set_property('device', args[1])
      streammux.set_property('width', width)
      streammux.set_property('height', height)
      streammux.set_property('batch-size', 1)
      streammux.set_property('batched-push-timeout', 4000000)
      pgie.set_property('config-file-path', "dstest1_pgie_config.txt")
      # Set sync = false to avoid late frame drops at the display-sink
      sink.set_property('sync', False)
  
      print("Adding elements to Pipeline \n")
      pipeline.add(source)
      pipeline.add(caps_v4l2src)
      pipeline.add(vidconvsrc)
      pipeline.add(nvvidconvsrc)
      pipeline.add(caps_vidconvsrc)
      pipeline.add(streammux)
      pipeline.add(pgie)
      pipeline.add(nvvidconv)
      pipeline.add(nvosd)
      pipeline.add(sink)
      if is_aarch64():
          pipeline.add(transform)
  
      # we link the elements together
      # v4l2src -> nvvideoconvert -> mux -> 
      # nvinfer -> nvvideoconvert -> nvosd -> video-renderer
      print("Linking elements in the Pipeline \n")
      source.link(caps_v4l2src)
      caps_v4l2src.link(vidconvsrc)
      vidconvsrc.link(nvvidconvsrc)
      nvvidconvsrc.link(caps_vidconvsrc)
  
      sinkpad = streammux.get_request_pad("sink_0")
      if not sinkpad:
          sys.stderr.write(" Unable to get the sink pad of streammux \n")
      srcpad = caps_vidconvsrc.get_static_pad("src")
      if not srcpad:
          sys.stderr.write(" Unable to get source pad of caps_vidconvsrc \n")
      srcpad.link(sinkpad)
      streammux.link(pgie)
      pgie.link(nvvidconv)
      nvvidconv.link(nvosd)
      if is_aarch64():
          nvosd.link(transform)
          transform.link(sink)
      else:
          nvosd.link(sink)
  
      # create an event loop and feed gstreamer bus mesages to it
      loop = GObject.MainLoop()
      bus = pipeline.get_bus()
      bus.add_signal_watch()
      bus.connect ("message", bus_call, loop)
  
      # Lets add probe to get informed of the meta data generated, we add probe to
      # the sink pad of the osd element, since by that time, the buffer would have
      # had got all the metadata.
      osdsinkpad = nvosd.get_static_pad("sink")
      if not osdsinkpad:
          sys.stderr.write(" Unable to get sink pad of nvosd \n")
  
      osdsinkpad.add_probe(Gst.PadProbeType.BUFFER, osd_sink_pad_buffer_probe, 0)
  
      # start play back and listen to events
      print("Starting pipeline \n")
      pipeline.set_state(Gst.State.PLAYING)
      try:
          loop.run()
      except:
          pass
      # cleanup
      pipeline.set_state(Gst.State.NULL)
  
  if __name__ == '__main__':
      sys.exit(main(sys.argv))
  
  