- 增加一个探头
GstElement* osd_sink_pad = gst_element_get_static_pad (osd, "sink"); gst_pad_add_probe (osd_sink_pad, GST_PAD_PROBE_TYPE_BUFFER, osd_sink_pad_buffer_probe, NULL, NULL);
- 实现osd_sink_pad_buffer_probe函数
可以设置的信息有：
识别对象的Bounding Box，边框、背景色等等；
识别对象的文字标签（字体、颜色、标示框）；
吾这里都设置为半透明，显得很高档。
static GstPadProbeReturn osd_sink_pad_buffer_probe (GstPad * pad, GstPadProbeInfo * probe_info, gpointer u_data) { GstBuffer *buf = (GstBuffer *) probe_info->data; NvDsFrameMeta *frame_meta = NULL; NvOSD_TextParams *text_params= NULL; NvOSD_RectParams *rect_params= NULL; NvDsObjectParams *obj_meta = NULL; static GQuark _nvdsmeta_quark = 0; if (!_nvdsmeta_quark) { //g_quark_to_string _nvdsmeta_quark = g_quark_from_static_string (NVDS_META_STRING); } while ((gst_meta = gst_buffer_iterate_meta (buf, &state))) { if (!gst_meta_api_type_has_tag (gst_meta->info->api, _nvdsmeta_quark)) { continue; } nvdsmeta = (NvDsMeta *) gst_meta; /* 只对解析类型的元感兴趣。 */ if (nvdsmeta->meta_type != NVDS_META_FRAME_INFO) { continue; } frame_meta = (NvDsFrameMeta *) nvdsmeta->meta_data; if (frame_meta == NULL) { return GST_PAD_PROBE_OK; } frame_meta->num_strings = 0; num_rects = frame_meta->num_rects; for (rect_index = 0; rect_index < num_rects; rect_index++) { /* 现在，使用上述信息，构造一个用于显示在边界框顶端的字串，在这里构造。*/ obj_meta = (NvDsObjectParams *) & frame_meta->obj_params[rect_index]; rect_params = &(obj_meta->rect_params); if (rect_params) { rect_params->has_bg_color = 1; rect_params->bg_color.red = 0.5; rect_params->bg_color.green = 0.0; rect_params->bg_color.blue = 0.0; rect_params->bg_color.alpha = 0.3; rect_params->border_color.red = 1.0; rect_params->border_color.green = 1.0; rect_params->border_color.blue = 0.0; rect_params->border_color.alpha = 1.0; } text_params = &(obj_meta->text_params); /* 丢弃管线的字串。测试表明一直为空。 */ if (text_params->display_text) { g_free (text_params->display_text); } text_params->display_text = g_malloc0 (MAX_DISPLAY_LEN); g_snprintf (text_params->display_text, MAX_DISPLAY_LEN, "%02d-%s", rect_index, pgie_classes_str[obj_meta->class_id]); /* 设置字串显示效果 */ text_params->x_offset = obj_meta->rect_params.left; text_params->y_offset = obj_meta->rect_params.top - 25; /* Font , font-color and font-size */ text_params->font_params.font_name = "Arial"; text_params->font_params.font_size = 12; text_params->font_params.font_color.red = 1.0; text_params->font_params.font_color.green = 1.0; text_params->font_params.font_color.blue = 1.0; text_params->font_params.font_color.alpha = 1.0; /* Text background color */ text_params->set_bg_clr = 1; text_params->text_bg_clr.red = 0.0; text_params->text_bg_clr.green = 0.0; text_params->text_bg_clr.blue = 0.5; text_params->text_bg_clr.alpha = 0.3; frame_meta->num_strings++; } } return GST_PAD_PROBE_OK; }
