extern "C" bool NvDsInferParseCustomYoloV2Tiny(
    std::vector<NvDsInferLayerInfo> const& outputLayersInfo,
    NvDsInferNetworkInfo const& networkInfo,
    NvDsInferParseDetectionParams const& detectionParams,
    std::vector<NvDsInferParseObjectInfo>& objectList)
{
    ...
}
CHECK_CUSTOM_PARSE_FUNC_PROTOTYPE(NvDsInferParseCustomYoloV2Tiny);

....
else if (m_ConfigBlocks.at(i).at("type") == "yolo") {
            nvinfer1::Dims prevTensorDims = previous->getDimensions();
            assert(prevTensorDims.d[1] == prevTensorDims.d[2]);
            TensorInfo& curYoloTensor = m_OutputTensors.at(outputTensorCount);
            curYoloTensor.gridSize = prevTensorDims.d[1];
            curYoloTensor.stride = m_InputW / curYoloTensor.gridSize;
            m_OutputTensors.at(outputTensorCount).volume = curYoloTensor.gridSize
                * curYoloTensor.gridSize
                * (curYoloTensor.numBBoxes * (5 + curYoloTensor.numClasses));
            std::string layerName = "yolo_" + std::to_string(i);
            curYoloTensor.blobName = layerName;
            nvinfer1::IPluginV2* yoloPlugin
                = new YoloLayerV3(m_OutputTensors.at(outputTensorCount).numBBoxes,
                                  m_OutputTensors.at(outputTensorCount).numClasses,
                                  m_OutputTensors.at(outputTensorCount).gridSize);
            assert(yoloPlugin != nullptr);
            nvinfer1::IPluginV2Layer* yolo =
                network.addPluginV2(&previous, 1, *yoloPlugin);
            assert(yolo != nullptr);
            yolo->setName(layerName.c_str());
            std::string inputVol = dimsToString(previous->getDimensions());
            previous = yolo->getOutput(0);
            assert(previous != nullptr);
            previous->setName(layerName.c_str());
            std::string outputVol = dimsToString(previous->getDimensions());
            network.markOutput(*previous);
            channels = getNumChannels(previous);
            tensorOutputs.push_back(yolo->getOutput(0));
            printLayerInfo(layerIndex, "yolo", inputVol, outputVol, std::to_string(weightPtr));
            ++outputTensorCount;
        }
...

GST_DEBUG_BIN_TO_DOT_FILE(pipeline, GST_DEBUG_GRAPH_SHOW_ALL, "dstest1-pipeline");

/* Create RTSP output bin */
rtsp_out_bin = gst_element_factory_make ("nvrtspoutsinkbin", "nvrtsp-renderer");

if (!rtsp_out_bin) {
  g_printerr ("Failed to create RTSP output elements. Exiting.\n");
  return -1;
}

g_object_set (G_OBJECT (rtsp_out_bin), "sync", TRUE, NULL);
g_object_set (G_OBJECT (rtsp_out_bin), "bitrate", 768000, NULL);
g_object_set (G_OBJECT (rtsp_out_bin), "rtsp-port", rtsp_port_num, NULL);
g_object_set (G_OBJECT (rtsp_out_bin), "enc-type", enc_type, NULL);

gst_bin_add_many (GST_BIN (pipeline), rtsp_out_bin, NULL);

static GstPadProbeReturn
osd_sink_pad_buffer_probe (GstPad * pad, GstPadProbeInfo * info,
    gpointer u_data)
{
  GstBuffer *buf = (GstBuffer *) info->data;
  NvDsFrameMeta *frame_meta = NULL;
  NvOSD_TextParams *txt_params = NULL;
  guint vehicle_count = 0;
  guint person_count = 0;
  gboolean is_first_object = TRUE;
  NvDsMetaList *l_frame, *l_obj;

  NvDsBatchMeta *batch_meta = gst_buffer_get_nvds_batch_meta (buf);
  if (!batch_meta) {
    // No batch meta attached.
    return GST_PAD_PROBE_OK;
  }

  //batch_meta : NvDsBatchMeta https://docs.nvidia.com/metropolis/deepstream/sdk-api/struct__NvDsBatchMeta.html
  //
  //l_frame : NvDsFrameMetaList, 本質是GList http://irtfweb.ifa.hawaii.edu/SoftwareDocs/gtk20/glib/glib-doubly-linked-lists.html#GList
  //   struct GList
  // {
  //   gpointer data;
  //   GList *next;
  //   GList *prev;
  // };

  for (l_frame = batch_meta->frame_meta_list; l_frame; l_frame = l_frame->next) {
    frame_meta = (NvDsFrameMeta *) l_frame->data;

    if (frame_meta == NULL) {
      // Ignore Null frame meta.
      continue;
    }

    is_first_object = TRUE;

    // frame_meta : NvDsFrameMeta https://docs.nvidia.com/metropolis/deepstream/sdk-api/struct__NvDsFrameMeta.html
    // l_obj : NvDsObjectMetaList * 本質是GList 
    // obj_meta : NvDsObjectMeta
    for (l_obj = frame_meta->obj_meta_list; l_obj; l_obj = l_obj->next) {
      NvDsObjectMeta *obj_meta = (NvDsObjectMeta *) l_obj->data;

      if (obj_meta == NULL) {
        // Ignore Null object.
        continue;
      }

      // obj_meta : NvDsObjectMeta
      // text_params : NvOSD_TextParams 描述物件的文字
      // line233 - 241應該是清掉原本的文字然後放入字定義的class名稱
      txt_params = &(obj_meta->text_params);
      if (txt_params->display_text)
        g_free (txt_params->display_text);

      txt_params->display_text = g_malloc0 (MAX_DISPLAY_LEN);

      g_snprintf (txt_params->display_text, MAX_DISPLAY_LEN, "%s ",
          pgie_classes_str[obj_meta->class_id]);

      if (obj_meta->class_id == PGIE_CLASS_ID_VEHICLE)
        vehicle_count++;
      if (obj_meta->class_id == PGIE_CLASS_ID_PERSON)
        person_count++;

      /* Now set the offsets where the string should appear */
      txt_params->x_offset = obj_meta->rect_params.left;
      txt_params->y_offset = obj_meta->rect_params.top - 25;

      /* Font , font-color and font-size */
      txt_params->font_params.font_name = "Serif";
      txt_params->font_params.font_size = 10;
      txt_params->font_params.font_color.red = 1.0;
      txt_params->font_params.font_color.green = 1.0;
      txt_params->font_params.font_color.blue = 1.0;
      txt_params->font_params.font_color.alpha = 1.0;

      /* Text background color */
      txt_params->set_bg_clr = 1;
      txt_params->text_bg_clr.red = 0.0;
      txt_params->text_bg_clr.green = 0.0;
      txt_params->text_bg_clr.blue = 0.0;
      txt_params->text_bg_clr.alpha = 1.0;

      /*
       * Ideally NVDS_EVENT_MSG_META should be attached to buffer by the
       * component implementing detection / recognition logic.
       * Here it demonstrates how to use / attach that meta data.
       */
      if (is_first_object && !(frame_number % frame_interval)) {
        /* Frequency of messages to be send will be based on use case.
         * Here message is being sent for first object every frame_interval(default=30).
         */

        NvDsEventMsgMeta *msg_meta =
            (NvDsEventMsgMeta *) g_malloc0 (sizeof (NvDsEventMsgMeta));
        msg_meta->bbox.top = obj_meta->rect_params.top;
        msg_meta->bbox.left = obj_meta->rect_params.left;
        msg_meta->bbox.width = obj_meta->rect_params.width;
        msg_meta->bbox.height = obj_meta->rect_params.height;
        msg_meta->frameId = frame_number;
        msg_meta->trackingId = obj_meta->object_id;
        msg_meta->confidence = obj_meta->confidence;
        generate_event_msg_meta (msg_meta, obj_meta->class_id, obj_meta);

        // 要增加自訂的meta data必須要先用            nvds_acquire_user_meta_from_pool (batch_meta);取得
        // https://docs.nvidia.com/metropolis/deepstream/dev-guide/text/DS_plugin_metadata.html#user-custom-metadata-addition-inside-nvdsbatchmeta

        NvDsUserMeta *user_event_meta =
            nvds_acquire_user_meta_from_pool (batch_meta);
        if (user_event_meta) {
          user_event_meta->user_meta_data = (void *) msg_meta;
          user_event_meta->base_meta.meta_type = NVDS_EVENT_MSG_META;
          user_event_meta->base_meta.copy_func =
              (NvDsMetaCopyFunc) meta_copy_func;
          user_event_meta->base_meta.release_func =
              (NvDsMetaReleaseFunc) meta_free_func;
          nvds_add_user_meta_to_frame (frame_meta, user_event_meta);
        } else {
          g_print ("Error in attaching event meta to buffer\n");
        }
        is_first_object = FALSE;
      }
    }
  }
  g_print ("Frame Number = %d "
      "Vehicle Count = %d Person Count = %d\n",
      frame_number, vehicle_count, person_count);
  frame_number++;

  return GST_PAD_PROBE_OK;
}

/* pgie_src_pad_buffer_probe will extract metadata received on pgie src pad
 * and update params for drawing rectangle, object information etc. We also
 * iterate through the object list and encode the cropped objects as jpeg
 * images and attach it as user meta to the respective objects.*/
static GstPadProbeReturn
pgie_src_pad_buffer_probe (GstPad * pad, GstPadProbeInfo * info, gpointer ctx)
{
  GstBuffer *buf = (GstBuffer *) info->data;
  GstMapInfo inmap = GST_MAP_INFO_INIT;
  if (!gst_buffer_map (buf, &inmap, GST_MAP_READ)) {
    GST_ERROR ("input buffer mapinfo failed");
    return GST_PAD_PROBE_DROP;
  }
  NvBufSurface *ip_surf = (NvBufSurface *) inmap.data;
  gst_buffer_unmap (buf, &inmap);

  NvDsObjectMeta *obj_meta = NULL;
  guint vehicle_count = 0;
  guint person_count = 0;
  NvDsMetaList *l_frame = NULL;
  NvDsMetaList *l_obj = NULL;
  NvDsBatchMeta *batch_meta = gst_buffer_get_nvds_batch_meta (buf);
  for (l_frame = batch_meta->frame_meta_list; l_frame != NULL;
      l_frame = l_frame->next) {
    NvDsFrameMeta *frame_meta = (NvDsFrameMeta *) (l_frame->data);
    /* For demonstration purposes, we will encode the first 10 frames. */
    if(frame_count <= 10) {
      NvDsObjEncUsrArgs frameData = { 0 };
      /* Preset */
      frameData.isFrame = 1;
      /* To be set by user */
      frameData.saveImg = save_img;
      frameData.attachUsrMeta = attach_user_meta;
      /* Set if Image scaling Required */
      frameData.scaleImg = FALSE;
      frameData.scaledWidth = 0;
      frameData.scaledHeight = 0;
      /* Quality */
      frameData.quality = 80;
      /* Main Function Call */
      nvds_obj_enc_process (ctx, &frameData, ip_surf, NULL, frame_meta);
    }
    guint num_rects = 0;
    for (l_obj = frame_meta->obj_meta_list; l_obj != NULL; l_obj = l_obj->next) {
      obj_meta = (NvDsObjectMeta *) (l_obj->data);
      if (obj_meta->class_id == PGIE_CLASS_ID_VEHICLE) {
        vehicle_count++;
        num_rects++;
      }
      if (obj_meta->class_id == PGIE_CLASS_ID_PERSON) {
        person_count++;
        num_rects++;
      }
      /* Conditions that user needs to set to encode the detected objects of
       * interest. Here, by default all the detected objects are encoded.
       * For demonstration, we will encode the first object in the frame. */
      if ((obj_meta->class_id == PGIE_CLASS_ID_PERSON
              || obj_meta->class_id == PGIE_CLASS_ID_VEHICLE)
          && num_rects == 1) {
        NvDsObjEncUsrArgs objData = { 0 };
        /* To be set by user */
        objData.saveImg = save_img;
        objData.attachUsrMeta = attach_user_meta;
        /* Set if Image scaling Required */
        objData.scaleImg = FALSE;
        objData.scaledWidth = 0;
        objData.scaledHeight = 0;
        /* Preset */
        objData.objNum = num_rects;
        /* Quality */
        objData.quality = 80;
        /*Main Function Call */
        nvds_obj_enc_process (ctx, &objData, ip_surf, obj_meta, frame_meta);
      }
    }
  }
  nvds_obj_enc_finish (ctx);
  frame_count++;
  return GST_PAD_PROBE_OK;
}

/* osd_sink_pad_buffer_probe will extract metadata received on OSD sink pad
 * and update params for drawing rectangle, object information. We also iterate
 * through the user meta of type "NVDS_CROP_IMAGE_META" to find image crop meta
 * and demonstrate how to access it.*/
static GstPadProbeReturn
osd_sink_pad_buffer_probe (GstPad * pad, GstPadProbeInfo * info,
    gpointer u_data)
{
  GstBuffer *buf = (GstBuffer *) info->data;

  guint num_rects = 0;
  NvDsObjectMeta *obj_meta = NULL;
  guint vehicle_count = 0;
  guint person_count = 0;
  NvDsMetaList *l_frame = NULL;
  NvDsMetaList *l_obj = NULL;
  NvDsDisplayMeta *display_meta = NULL;
  NvDsBatchMeta *batch_meta = gst_buffer_get_nvds_batch_meta (buf);
  g_print ("Running osd_sink_pad_buffer_probe...\n");
  for (l_frame = batch_meta->frame_meta_list; l_frame != NULL;
      l_frame = l_frame->next) {
    NvDsFrameMeta *frame_meta = (NvDsFrameMeta *) (l_frame->data);
    int offset = 0;
    /* To verify  encoded metadata of cropped frames, we iterate through the
    * user metadata of each frame and if a metadata of the type
    * 'NVDS_CROP_IMAGE_META' is found then we write that to a file as
    * implemented below.
    */
    char fileFrameNameString[FILE_NAME_SIZE];
    const char *osd_string = "OSD";

    /* For Demonstration Purposes we are writing metadata to jpeg images of
      * the first 10 frames only.
      * The files generated have an 'OSD' prefix. */
    if (frame_number < 11) {
      NvDsUserMetaList *usrMetaList = frame_meta->frame_user_meta_list;
      FILE *file;
      int stream_num = 0;
      while (usrMetaList != NULL) {
        NvDsUserMeta *usrMetaData = (NvDsUserMeta *) usrMetaList->data;
        if (usrMetaData->base_meta.meta_type == NVDS_CROP_IMAGE_META) {
          snprintf (fileFrameNameString, FILE_NAME_SIZE, "%s_frame_%d_%d.jpg",
              osd_string, frame_number, stream_num++);
          NvDsObjEncOutParams *enc_jpeg_image =
              (NvDsObjEncOutParams *) usrMetaData->user_meta_data;
          /* Write to File */
          file = fopen (fileFrameNameString, "wb");
          fwrite (enc_jpeg_image->outBuffer, sizeof (uint8_t),
              enc_jpeg_image->outLen, file);
          fclose (file);
        }
        usrMetaList = usrMetaList->next;
      }
    }
    for (l_obj = frame_meta->obj_meta_list; l_obj != NULL; l_obj = l_obj->next) {
      obj_meta = (NvDsObjectMeta *) (l_obj->data);
      if (obj_meta->class_id == PGIE_CLASS_ID_VEHICLE) {
        vehicle_count++;
        num_rects++;
      }
      if (obj_meta->class_id == PGIE_CLASS_ID_PERSON) {
        person_count++;
        num_rects++;
      }
      /* To verify  encoded metadata of cropped objects, we iterate through the
       * user metadata of each object and if a metadata of the type
       * 'NVDS_CROP_IMAGE_META' is found then we write that to a file as
       * implemented below.
       */
      char fileObjNameString[FILE_NAME_SIZE];

      /* For Demonstration Purposes we are writing metadata to jpeg images of
       * vehicles or persons for the first 100 frames only.
       * The files generated have a 'OSD' prefix. */
      if (frame_number < 100 && (obj_meta->class_id == PGIE_CLASS_ID_PERSON
              || obj_meta->class_id == PGIE_CLASS_ID_VEHICLE)) {
        NvDsUserMetaList *usrMetaList = obj_meta->obj_user_meta_list;
        FILE *file;
        while (usrMetaList != NULL) {
          NvDsUserMeta *usrMetaData = (NvDsUserMeta *) usrMetaList->data;
          if (usrMetaData->base_meta.meta_type == NVDS_CROP_IMAGE_META) {
            NvDsObjEncOutParams *enc_jpeg_image =
                (NvDsObjEncOutParams *) usrMetaData->user_meta_data;

            snprintf (fileObjNameString, FILE_NAME_SIZE, "%s_%d_%d_%d_%s.jpg",
                osd_string, frame_number, frame_meta->batch_id, num_rects,
                obj_meta->obj_label);
            /* Write to File */
            file = fopen (fileObjNameString, "wb");
            fwrite (enc_jpeg_image->outBuffer, sizeof (uint8_t),
                enc_jpeg_image->outLen, file);
            fclose (file);
            usrMetaList = NULL;
          } else {
            usrMetaList = usrMetaList->next;
          }
        }
      }
    }
    display_meta = nvds_acquire_display_meta_from_pool (batch_meta);
    NvOSD_TextParams *txt_params = &display_meta->text_params[0];
    txt_params->display_text = g_malloc0 (MAX_DISPLAY_LEN);
    offset =
        snprintf (txt_params->display_text, MAX_DISPLAY_LEN, "Person = %d ",
        person_count);
    offset =
        snprintf (txt_params->display_text + offset, MAX_DISPLAY_LEN,
        "Vehicle = %d ", vehicle_count);

    /* Now set the offsets where the string should appear */
    txt_params->x_offset = 10;
    txt_params->y_offset = 12;

    /* Font , font-color and font-size */
    txt_params->font_params.font_name = "Serif";
    txt_params->font_params.font_size = 10;
    txt_params->font_params.font_color.red = 1.0;
    txt_params->font_params.font_color.green = 1.0;
    txt_params->font_params.font_color.blue = 1.0;
    txt_params->font_params.font_color.alpha = 1.0;

    /* Text background color */
    txt_params->set_bg_clr = 1;
    txt_params->text_bg_clr.red = 0.0;
    txt_params->text_bg_clr.green = 0.0;
    txt_params->text_bg_clr.blue = 0.0;
    txt_params->text_bg_clr.alpha = 1.0;

    nvds_add_display_meta_to_frame (frame_meta, display_meta);
  }
  g_print ("Frame Number = %d Number of objects = %d "
      "Vehicle Count = %d Person Count = %d\n",
      frame_number, num_rects, vehicle_count, person_count);
  frame_number++;
  return GST_PAD_PROBE_OK;
}

/** set the user metadata type */
#define NVDS_USER_FRAME_META_EXAMPLE (nvds_get_user_meta_type("NVIDIA.NVINFER.USER_META"))
NvDsMetaType user_meta_type = NVDS_USER_FRAME_META_EXAMPLE;

/* copy function set by user. "data" holds a pointer to NvDsUserMeta*/
static gpointer copy_user_meta(gpointer data, gpointer user_data)
{
  NvDsUserMeta *user_meta = (NvDsUserMeta *)data;
  gchar *src_user_metadata = (gchar*)user_meta->user_meta_data;
  gchar *dst_user_metadata = (gchar*)g_malloc0(USER_ARRAY_SIZE);
  memcpy(dst_user_metadata, src_user_metadata, USER_ARRAY_SIZE);
  return (gpointer)dst_user_metadata;
}

/* release function set by user. "data" holds a pointer to NvDsUserMeta*/
static void release_user_meta(gpointer data, gpointer user_data)
{
  NvDsUserMeta *user_meta = (NvDsUserMeta *) data;
  if(user_meta->user_meta_data) {
    g_free(user_meta->user_meta_data);
    user_meta->user_meta_data = NULL;
  }
}

conn_handle = msgapi_connect_ptr((char *)"url;port;username;password",(nvds_msgapi_connect_cb_t) sample_msgapi_connect_cb, (char *)CFG_FILE);