overlay: optimize cache at the GstVideoOverlayRectangle level.

We previously assumed that an overlay composition changed if the number
of overlay rectangles in there actually changed, or that the rectangle
was updated, and thus its seqnum was also updated.

Now, we can cope with cases where the GstVideoOverlayComposition grew
by one or a few more overlay rectangles, and the initial overlay rectangles
are kept as is.

gst-libs/gst/vaapi/gstvaapicontext.c

@@ -54,6 +54,7 @@ struct _GstVaapiOverlayRectangle {
     GstVaapiSubpicture *subpicture;
     GstVaapiRectangle   render_rect;
     guint               seq_num;
+    GstVideoOverlayRectangle *rect;
     guint               is_associated   : 1;
 };
 
@@ -62,7 +63,8 @@ struct _GstVaapiContextPrivate {
     VAConfigID          config_id;
     GPtrArray          *surfaces;
     GstVaapiVideoPool  *surfaces_pool;
-    GPtrArray          *overlay;
+    GPtrArray          *overlays[2];
+    guint               overlay_id;
     GstVaapiProfile     profile;
     GstVaapiEntrypoint  entrypoint;
     guint               width;
@@ -94,6 +96,14 @@ get_max_ref_frames(GstVaapiProfile profile)
     return ref_frames;
 }
 
+static inline void
+gst_video_overlay_rectangle_replace(GstVideoOverlayRectangle **old_rect_ptr,
+    GstVideoOverlayRectangle *new_rect)
+{
+    gst_mini_object_replace((GstMiniObject **)old_rect_ptr,
+        GST_MINI_OBJECT_CAST(new_rect));
+}
+
 #define overlay_rectangle_ref(overlay) \
     gst_vaapi_mini_object_ref(GST_VAAPI_MINI_OBJECT(overlay))
 
@@ -138,6 +148,7 @@ overlay_rectangle_new(GstVideoOverlayRectangle *rect, GstVaapiContext *context)
 
     overlay->context    = context;
     overlay->seq_num    = gst_video_overlay_rectangle_get_seqnum(rect);
+    overlay->rect       = gst_video_overlay_rectangle_ref(rect);
 
     overlay->subpicture = gst_vaapi_subpicture_new_from_overlay_rectangle(
         GST_VAAPI_OBJECT_DISPLAY(context), rect);
@@ -166,6 +177,8 @@ error:
 static void
 overlay_rectangle_finalize(GstVaapiOverlayRectangle *overlay)
 {
+    gst_video_overlay_rectangle_unref(overlay->rect);
+
     if (overlay->subpicture) {
         overlay_rectangle_deassociate(overlay);
         g_object_unref(overlay->subpicture);
@@ -216,6 +229,25 @@ overlay_rectangle_deassociate(GstVaapiOverlayRectangle *overlay)
     return n_associated == 0;
 }
 
+static gboolean
+overlay_rectangle_changed_pixels(GstVaapiOverlayRectangle *overlay,
+    GstVideoOverlayRectangle *rect)
+{
+    if (overlay->seq_num == gst_video_overlay_rectangle_get_seqnum(rect))
+        return FALSE;
+    return TRUE;
+}
+
+static gboolean
+overlay_rectangle_update(GstVaapiOverlayRectangle *overlay,
+    GstVideoOverlayRectangle *rect)
+{
+    if (overlay_rectangle_changed_pixels(overlay, rect))
+        return FALSE;
+    gst_video_overlay_rectangle_replace(&overlay->rect, rect);
+    return TRUE;
+}
+
 static inline GPtrArray *
 overlay_new(void)
 {
@@ -241,12 +273,35 @@ overlay_clear(GPtrArray *overlay)
         g_ptr_array_remove_range(overlay, 0, overlay->len);
 }
 
+static GstVaapiOverlayRectangle *
+overlay_lookup(GPtrArray *overlays, GstVideoOverlayRectangle *rect)
+{
+    guint i;
+
+    for (i = 0; i < overlays->len; i++) {
+        GstVaapiOverlayRectangle * const overlay =
+            g_ptr_array_index(overlays, i);
+
+        if (overlay->rect == rect)
+            return overlay;
+    }
+    return NULL;
+}
+
 static void
-gst_vaapi_context_destroy_overlay(GstVaapiContext *context)
+gst_vaapi_context_clear_overlay(GstVaapiContext *context)
 {
     GstVaapiContextPrivate * const priv = context->priv;
 
-    overlay_clear(priv->overlay);
+    overlay_clear(priv->overlays[0]);
+    overlay_clear(priv->overlays[1]);
+    priv->overlay_id = 0;
+}
+
+static inline void
+gst_vaapi_context_destroy_overlay(GstVaapiContext *context)
+{
+    gst_vaapi_context_clear_overlay(context);
 }
 
 static void
@@ -317,10 +372,10 @@ gst_vaapi_context_create_overlay(GstVaapiContext *context)
 {
     GstVaapiContextPrivate * const priv = context->priv;
 
-    if (!priv->overlay)
+    if (!priv->overlays[0] || !priv->overlays[1])
         return FALSE;
 
-    overlay_clear(priv->overlay);
+    gst_vaapi_context_clear_overlay(context);
     return TRUE;
 }
 
@@ -476,7 +531,8 @@ gst_vaapi_context_finalize(GObject *object)
     GstVaapiContext * const context = GST_VAAPI_CONTEXT(object);
     GstVaapiContextPrivate * const priv = context->priv;
 
-    overlay_destroy(&priv->overlay);
+    overlay_destroy(&priv->overlays[0]);
+    overlay_destroy(&priv->overlays[1]);
     gst_vaapi_context_destroy(context);
     gst_vaapi_context_destroy_surfaces(context);
 
@@ -615,7 +671,8 @@ gst_vaapi_context_init(GstVaapiContext *context)
     priv->config_id     = VA_INVALID_ID;
     priv->surfaces      = NULL;
     priv->surfaces_pool = NULL;
-    priv->overlay       = overlay_new();
+    priv->overlays[0]   = overlay_new();
+    priv->overlays[1]   = overlay_new();
     priv->profile       = 0;
     priv->entrypoint    = 0;
     priv->width         = 0;
@@ -956,33 +1013,6 @@ gst_vaapi_context_find_surface_by_id(GstVaapiContext *context, GstVaapiID id)
     return NULL;
 }
 
-/* Check if composition changed */
-static gboolean
-gst_vaapi_context_composition_changed(
-    GstVaapiContext            *context,
-    GstVideoOverlayComposition *composition
-)
-{
-    GstVaapiContextPrivate * const priv = context->priv;
-    GstVaapiOverlayRectangle *overlay;
-    GstVideoOverlayRectangle *rect;
-    guint i, n_rectangles;
-
-    n_rectangles = gst_video_overlay_composition_n_rectangles(composition);
-    if (priv->overlay->len != n_rectangles)
-        return TRUE;
-
-    for (i = 0; i < n_rectangles; i++) {
-        rect = gst_video_overlay_composition_get_rectangle(composition, i);
-        g_return_val_if_fail(rect, TRUE);
-        overlay = g_ptr_array_index(priv->overlay, i);
-        g_return_val_if_fail(overlay, TRUE);
-        if (overlay->seq_num != gst_video_overlay_rectangle_get_seqnum(rect))
-            return TRUE;
-    }
-    return FALSE;
-}
-
 /**
  * gst_vaapi_context_apply_composition:
  * @context: a #GstVaapiContext
@@ -1003,6 +1033,7 @@ gst_vaapi_context_apply_composition(
 )
 {
     GstVaapiContextPrivate *priv;
+    GPtrArray *curr_overlay, *next_overlay;
     guint i, n_rectangles;
 
     g_return_val_if_fail(GST_VAAPI_IS_CONTEXT(context), FALSE);
@@ -1013,14 +1044,13 @@ gst_vaapi_context_apply_composition(
         return FALSE;
 
     if (!composition) {
-        if (priv->overlay->len > 0)
+        gst_vaapi_context_clear_overlay(context);
-            overlay_clear(priv->overlay);
         return TRUE;
     }
-    else if (!gst_vaapi_context_composition_changed(context, composition))
-        return TRUE;
 
-    overlay_clear(priv->overlay);
+    curr_overlay = priv->overlays[priv->overlay_id];
+    next_overlay = priv->overlays[priv->overlay_id ^ 1];
+    overlay_clear(next_overlay);
 
     n_rectangles = gst_video_overlay_composition_n_rectangles(composition);
     for (i = 0; i < n_rectangles; i++) {
@@ -1028,16 +1058,24 @@ gst_vaapi_context_apply_composition(
             gst_video_overlay_composition_get_rectangle(composition, i);
         GstVaapiOverlayRectangle *overlay;
 
-        overlay = overlay_rectangle_new(rect, context);
+        overlay = overlay_lookup(curr_overlay, rect);
-        if (!overlay) {
+        if (overlay && overlay_rectangle_update(overlay, rect))
-            GST_WARNING("could not create VA overlay rectangle");
+            overlay_rectangle_ref(overlay);
-            goto error;
+        else {
+            overlay = overlay_rectangle_new(rect, context);
+            if (!overlay) {
+                GST_WARNING("could not create VA overlay rectangle");
+                goto error;
+            }
         }
-        g_ptr_array_add(priv->overlay, overlay);
+        g_ptr_array_add(next_overlay, overlay);
     }
+
+    overlay_clear(curr_overlay);
+    priv->overlay_id ^= 1;
     return TRUE;
 
 error:
-    overlay_clear(priv->overlay);
+    gst_vaapi_context_clear_overlay(context);
     return FALSE;
 }