analytics: Make GstTensor more suitable for inline allocation

GstTensor contained two fields (data, dims) that were dynamicallay allocated. For
data it's for a GstBuffer and we have pool for efficient memory management. For
dims it's a small array to store the dimension of the tensor. The dims field
can be allocated inplace by moving it at the end of the structure. This will
allow a better memory management when GstTensor is stored in an analytics meta
which will take advantage of the _clear interface for re-use.

- New api to allocate and free GstTensor
To continue to support use-cases where GstTensor is not stored in an
analytics-meta we provide gst_tensor_alloc, gst_tensor_alloc_n and
gst_tensor_free that will facilitate memory management.
- Make GstTensor a boxed type

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6000>

subprojects/gst-plugins-bad/ext/onnx/gstonnxclient.cpp

@@ -333,7 +333,7 @@ GstOnnxClient::GstOnnxClient (GstElement *debug_parent):debug_parent(debug_paren
         gst_tensor_meta_get_info (),
         NULL);
     tmeta->num_tensors = num_tensors;
-    tmeta->tensor = (GstTensor *) g_malloc (num_tensors * sizeof (GstTensor));
+    tmeta->tensors = g_new (GstTensor *, num_tensors);
     bool hasIds = outputIds.size () == num_tensors;
     for (size_t i = 0; i < num_tensors; i++) {
       Ort::Value outputTensor = std::move (outputs[i]);
@@ -341,14 +341,15 @@ GstOnnxClient::GstOnnxClient (GstElement *debug_parent):debug_parent(debug_paren
       ONNXTensorElementDataType tensorType =
           outputTensor.GetTensorTypeAndShapeInfo ().GetElementType ();
 
-      GstTensor *tensor = &tmeta->tensor[i];
+      auto tensorShape = outputTensor.GetTensorTypeAndShapeInfo ().GetShape ();
+      GstTensor *tensor = gst_tensor_alloc (tensorShape.size ());
+      tmeta->tensors[i] = tensor;
+
       if (hasIds)
         tensor->id = outputIds[i];
       else
         tensor->id = 0;
-      auto tensorShape = outputTensor.GetTensorTypeAndShapeInfo ().GetShape ();
       tensor->num_dims = tensorShape.size ();
-      tensor->dims = g_new (gsize, tensor->num_dims);
       tensor->batch_size = 1;
 
       for (size_t j = 0; j < tensorShape.size (); ++j)

subprojects/gst-plugins-bad/gst-libs/gst/analytics/gsttensor.c

@@ -0,0 +1,92 @@
+/* GStreamer
+ * Copyright (C) 2023 Collabora Ltd
+ *
+ * gstanalyticsmeta.c
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gsttensor.h"
+
+#define GST_TENSOR_SIZE(num_dims) \
+  (sizeof (GstTensor) + (sizeof (gsize) * num_dims))
+
+G_DEFINE_BOXED_TYPE (GstTensor, gst_tensor,
+    (GBoxedCopyFunc) gst_tensor_copy, (GBoxedFreeFunc) gst_tensor_free);
+
+/**
+ * gst_tensor_alloc: (constructor)
+ * @num_dims: Number of dimension of the tensors
+ *
+ * Allocate a tensor with @num_dims dimensions.
+ *
+ * Returns: (transfer full) (not nullable): tensor allocated
+ *
+ * Since: 1.26
+ */
+GstTensor *
+gst_tensor_alloc (gsize num_dims)
+{
+  GstTensor *tensor = g_malloc0 (GST_TENSOR_SIZE (num_dims));
+
+  tensor->num_dims = num_dims;
+
+  return tensor;
+}
+}
+
+/**
+ * gst_tensor_free:
+ * @tensor: (in) (transfer full): pointer to tensor to free
+ *
+ * Free tensor
+ *
+ * Since: 1.26
+ */
+void
+gst_tensor_free (GstTensor * tensor)
+{
+  if (tensor->data != NULL) {
+    gst_buffer_unref (tensor->data);
+  }
+  g_free (tensor);
+}
+
+/**
+ * gst_tensor_copy:
+ * @tensor: (transfer none) (nullable): a #GstTensor to be copied
+ *
+ * Create a copy of @tensor.
+ *
+ * Returns: (transfer full) (nullable): a new #GstTensor
+ *
+ * Since: 1.26
+ */
+GstTensor *
+gst_tensor_copy (const GstTensor * tensor)
+{
+  GstTensor *copy = NULL;
+  if (tensor) {
+    copy = (GstTensor *) g_memdup2 (tensor, GST_TENSOR_SIZE (tensor->num_dims));
+    if (copy->data)
+      gst_buffer_ref (copy->data);
+  }
+
+  return copy;
+}

subprojects/gst-plugins-bad/gst-libs/gst/analytics/gsttensor.h

@@ -115,15 +115,33 @@ typedef enum _GstTensorLayout
 typedef struct _GstTensor
 {
   GQuark id;
-  gsize num_dims;
-  gsize *dims;
   GstTensorDimOrder dims_order;
   GstTensorLayout layout;
   GstTensorDataType data_type;
   gsize batch_size;
   GstBuffer *data;
+  gsize num_dims;
+  gsize dims[];
 } GstTensor;
 
+G_BEGIN_DECLS
+
+#define GST_TYPE_TENSOR (gst_tensor_get_type())
+
+GST_ANALYTICS_META_API
+GstTensor * gst_tensor_alloc (gsize num_dims);
+
+GST_ANALYTICS_META_API
+void gst_tensor_free (GstTensor * tensor);
+
+GST_ANALYTICS_META_API
+GstTensor * gst_tensor_copy (const GstTensor * tensor);
+
+GST_ANALYTICS_META_API
+GType gst_tensor_get_type (void);
+
 #define GST_TENSOR_MISSING_ID -1
 
+G_END_DECLS
+
 #endif /* __GST_TENSOR_H__ */

subprojects/gst-plugins-bad/gst-libs/gst/analytics/gsttensormeta.c

@@ -28,7 +28,7 @@ gst_tensor_meta_init (GstMeta * meta, gpointer params, GstBuffer * buffer)
   GstTensorMeta *tmeta = (GstTensorMeta *) meta;
 
   tmeta->num_tensors = 0;
-  tmeta->tensor = NULL;
+  tmeta->tensors = NULL;
 
   return TRUE;
 }
@@ -39,10 +39,9 @@ gst_tensor_meta_free (GstMeta * meta, GstBuffer * buffer)
   GstTensorMeta *tmeta = (GstTensorMeta *) meta;
 
   for (int i = 0; i < tmeta->num_tensors; i++) {
-    g_free (tmeta->tensor[i].dims);
-    gst_buffer_unref (tmeta->tensor[i].data);
+    gst_tensor_free (tmeta->tensors[i]);
   }
-  g_free (tmeta->tensor);
+  g_free (tmeta->tensors);
 }
 
 GType
@@ -81,7 +80,7 @@ gint
 gst_tensor_meta_get_index_from_id (GstTensorMeta * meta, GQuark id)
 {
   for (int i = 0; i < meta->num_tensors; ++i) {
-    if ((meta->tensor + i)->id == id)
+    if (meta->tensors[i]->id == id)
       return i;
   }
 

subprojects/gst-plugins-bad/gst-libs/gst/analytics/gsttensormeta.h

@@ -45,7 +45,7 @@ typedef struct _GstTensorMeta
   GstMeta meta;
 
   gsize num_tensors;
-  GstTensor *tensor;
+  GstTensor **tensors;
 } GstTensorMeta;
 
 G_BEGIN_DECLS

subprojects/gst-plugins-bad/gst-libs/gst/analytics/meson.build

@@ -3,7 +3,8 @@ analytics_sources = files( 'gstanalyticsmeta.c',
                               'gstanalyticsobjectdetectionmtd.c',
                               'gstanalyticsobjecttrackingmtd.c',
                               'gstanalyticssegmentationmtd.c',
-                              'gsttensormeta.c')
+                              'gsttensormeta.c',
+                              'gsttensor.c')
 
 analytics_headers = files(    'analytics.h',
                               'gstanalyticsmeta.h',

subprojects/gst-plugins-bad/gst/tensordecoders/gstssdobjectdetector.c

@@ -442,21 +442,21 @@ DEFINE_GET_FUNC (guint32, UINT32_MAX)
     return;
   }
 
-  if (!gst_buffer_map (tmeta->tensor[numdetect_index].data, &numdetect_map,
+  if (!gst_buffer_map (tmeta->tensors[numdetect_index]->data, &numdetect_map,
           GST_MAP_READ)) {
     GST_ERROR_OBJECT (self, "Failed to map tensor memory for index %d",
         numdetect_index);
     goto cleanup;
   }
 
-  if (!gst_buffer_map (tmeta->tensor[boxes_index].data, &boxes_map,
+  if (!gst_buffer_map (tmeta->tensors[boxes_index]->data, &boxes_map,
           GST_MAP_READ)) {
     GST_ERROR_OBJECT (self, "Failed to map tensor memory for index %d",
         boxes_index);
     goto cleanup;
   }
 
-  if (!gst_buffer_map (tmeta->tensor[scores_index].data, &scores_map,
+  if (!gst_buffer_map (tmeta->tensors[scores_index]->data, &scores_map,
           GST_MAP_READ)) {
     GST_ERROR_OBJECT (self, "Failed to map tensor memory for index %d",
         scores_index);
@@ -464,14 +464,14 @@ DEFINE_GET_FUNC (guint32, UINT32_MAX)
   }
 
   if (classes_index != GST_TENSOR_MISSING_ID &&
-      !gst_buffer_map (tmeta->tensor[classes_index].data, &classes_map,
+      !gst_buffer_map (tmeta->tensors[classes_index]->data, &classes_map,
           GST_MAP_READ)) {
     GST_DEBUG_OBJECT (self, "Failed to map tensor memory for index %d",
         classes_index);
   }
 
 
-  if (!get_guint32_at_index (&tmeta->tensor[numdetect_index], &numdetect_map,
+  if (!get_guint32_at_index (tmeta->tensors[numdetect_index], &numdetect_map,
           0, &num_detections)) {
     GST_ERROR_OBJECT (self, "Failed to get the number of detections");
     goto cleanup;
@@ -488,7 +488,7 @@ DEFINE_GET_FUNC (guint32, UINT32_MAX)
     GQuark label = 0;
     GstAnalyticsODMtd odmtd;
 
-    if (!get_float_at_index (&tmeta->tensor[numdetect_index], &scores_map,
+    if (!get_float_at_index (tmeta->tensors[numdetect_index], &scores_map,
             i, &score))
       continue;
 
@@ -496,16 +496,16 @@ DEFINE_GET_FUNC (guint32, UINT32_MAX)
     if (score < self->score_threshold)
       continue;
 
-    if (!get_float_at_index (&tmeta->tensor[boxes_index], &boxes_map,
+    if (!get_float_at_index (tmeta->tensors[boxes_index], &boxes_map,
             i * 4, &y))
       continue;
-    if (!get_float_at_index (&tmeta->tensor[boxes_index], &boxes_map,
+    if (!get_float_at_index (tmeta->tensors[boxes_index], &boxes_map,
             i * 4 + 1, &x))
       continue;
-    if (!get_float_at_index (&tmeta->tensor[boxes_index], &boxes_map,
+    if (!get_float_at_index (tmeta->tensors[boxes_index], &boxes_map,
             i * 4 + 2, &bheight))
       continue;
-    if (!get_float_at_index (&tmeta->tensor[boxes_index], &boxes_map,
+    if (!get_float_at_index (tmeta->tensors[boxes_index], &boxes_map,
             i * 4 + 3, &bwidth))
       continue;
 
@@ -517,7 +517,7 @@ DEFINE_GET_FUNC (guint32, UINT32_MAX)
     }
 
     if (self->labels && classes_map.memory &&
-        get_guint32_at_index (&tmeta->tensor[classes_index], &classes_map,
+        get_guint32_at_index (tmeta->tensors[classes_index], &classes_map,
             i, &bclass)) {
       if (bclass < self->labels->len)
         label = g_array_index (self->labels, GQuark, bclass);
@@ -540,13 +540,13 @@ DEFINE_GET_FUNC (guint32, UINT32_MAX)
 cleanup:
 
   if (numdetect_map.memory)
-    gst_buffer_unmap (tmeta->tensor[numdetect_index].data, &numdetect_map);
+    gst_buffer_unmap (tmeta->tensors[numdetect_index]->data, &numdetect_map);
   if (classes_map.memory)
-    gst_buffer_unmap (tmeta->tensor[classes_index].data, &classes_map);
+    gst_buffer_unmap (tmeta->tensors[classes_index]->data, &classes_map);
   if (scores_map.memory)
-    gst_buffer_unmap (tmeta->tensor[scores_index].data, &scores_map);
+    gst_buffer_unmap (tmeta->tensors[scores_index]->data, &scores_map);
   if (boxes_map.memory)
-    gst_buffer_unmap (tmeta->tensor[boxes_index].data, &boxes_map);
+    gst_buffer_unmap (tmeta->tensors[boxes_index]->data, &boxes_map);
 }