[DLStreamer] Fix memory leak in RegionOfInterest (open-edge-platform#1170)

Co-authored-by: Tomasz Bujewski <[email protected]>

Author: yunowo

libraries/dl-streamer/include/dlstreamer/gst/videoanalytics/region_of_interest.h

@@ -21,6 +21,7 @@
 #include <gst/video/gstvideometa.h>
 
 #include <cassert>
+#include <memory>
 #include <stdexcept>
 #include <string>
 #include <vector>
@@ -244,8 +245,11 @@ class RegionOfInterest {
         while (gst_analytics_relation_meta_get_direct_related(od_meta.meta, od_meta.id, GST_ANALYTICS_REL_TYPE_CONTAIN,
                                                               GST_ANALYTICS_MTD_TYPE_ANY, &state, &handle)) {
             GstStructure *s = GVA::Tensor::convert_to_tensor(handle);
-            if (s != nullptr)
+            if (s != nullptr) {
+                auto shared_s = std::shared_ptr<GstStructure>(s, gst_structure_free);
                 _tensors.emplace_back(s);
+                _converted_structures.push_back(shared_s);
+            }
         }
     }
 
@@ -371,6 +375,12 @@ class RegionOfInterest {
      * obtained from GstVideoRegionOfInterestMeta
      */
     std::vector<Tensor> _tensors;
+
+    /**
+     * @brief vector of GstStructure shared pointers that were allocated by convert_to_tensor.
+     */
+    std::vector<std::shared_ptr<GstStructure>> _converted_structures;
+
     /**
      * @brief last added detection Tensor instance, defined as Tensor with name set to "detection"
      */

libraries/dl-streamer/include/dlstreamer/gst/videoanalytics/video_frame.h

@@ -332,21 +332,30 @@ class VideoFrame {
     }
 
     std::vector<RegionOfInterest> get_regions() const {
-        std::vector<RegionOfInterest> regions;
-        gpointer state = NULL;
-        GstAnalyticsRelationMeta *relation_meta;
-        GstVideoRegionOfInterestMeta *roi_meta;
-        GstAnalyticsODMtd od_mtd;
-
-        relation_meta = gst_buffer_get_analytics_relation_meta(buffer);
+        GstAnalyticsRelationMeta *relation_meta = gst_buffer_get_analytics_relation_meta(buffer);
 
         if (!relation_meta) {
             return {};
         }
 
+        // Count regions to pre-allocate vector capacity
+        gpointer state = NULL;
+        GstAnalyticsODMtd od_mtd;
+        size_t count = 0;
+        while (
+            gst_analytics_relation_meta_iterate(relation_meta, &state, gst_analytics_od_mtd_get_mtd_type(), &od_mtd)) {
+            ++count;
+        }
+
+        // Pre-allocate vector to avoid reallocation during emplace_back
+        std::vector<RegionOfInterest> regions;
+        regions.reserve(count);
+
+        // Construct RegionOfInterest objects
+        state = NULL;
         while (
             gst_analytics_relation_meta_iterate(relation_meta, &state, gst_analytics_od_mtd_get_mtd_type(), &od_mtd)) {
-            roi_meta = gst_buffer_get_video_region_of_interest_meta_id(buffer, od_mtd.id);
+            GstVideoRegionOfInterestMeta *roi_meta = gst_buffer_get_video_region_of_interest_meta_id(buffer, od_mtd.id);
             if (!roi_meta) {
                 throw std::runtime_error(
                     "GVA::VideoFrame: Failed to get video region of interest meta for object detection metadata");