From 672a30d0def1f02b6911892ddd4dfc854e1727d3 Mon Sep 17 00:00:00 2001
From: He Junyan <junyan.he@intel.com>
Date: Mon, 16 Nov 2020 23:53:39 +0800
Subject: [PATCH] va: basedec: fallback to system memory if downstream caps is
 any.

When the downstream element reports an ANY caps, and it also fails to
support VideoMeta, we should fallback to the system memory.
Note: the basetransform kind elements never return valid allocation
query before set_caps(). So, if a basetransform return an ANY sink
caps, we always fallback to system memory for it.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1711>
---
 sys/va/gstvabasedec.c | 52 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/sys/va/gstvabasedec.c b/sys/va/gstvabasedec.c
index b33e854..3e9dcbd 100644
--- a/sys/va/gstvabasedec.c
+++ b/sys/va/gstvabasedec.c
@@ -438,6 +438,22 @@ _default_video_format_from_chroma (guint chroma_type)
   }
 }
 
+/* Check whether the downstream supports VideoMeta; if not, we need to
+ * fallback to the system memory. */
+static gboolean
+_downstream_has_video_meta (GstVaBaseDec * base, GstCaps * caps)
+{
+  GstQuery *query;
+  gboolean ret = FALSE;
+
+  query = gst_query_new_allocation (caps, FALSE);
+  if (gst_pad_peer_query (GST_VIDEO_DECODER_SRC_PAD (base), query))
+    ret = gst_query_find_allocation_meta (query, GST_VIDEO_META_API_TYPE, NULL);
+  gst_query_unref (query);
+
+  return ret;
+}
+
 void
 gst_va_base_dec_get_preferred_format_and_caps_features (GstVaBaseDec * base,
     GstVideoFormat * format, GstCapsFeatures ** capsfeatures)
@@ -447,9 +463,18 @@ gst_va_base_dec_get_preferred_format_and_caps_features (GstVaBaseDec * base,
   GstStructure *structure;
   const GValue *v_format;
   guint num_structures, i;
+  gboolean is_any;
 
   g_return_if_fail (base);
 
+  /* verify if peer caps is any */
+  {
+    peer_caps =
+        gst_pad_peer_query_caps (GST_VIDEO_DECODER_SRC_PAD (base), NULL);
+    is_any = gst_caps_is_any (peer_caps);
+    gst_clear_caps (&peer_caps);
+  }
+
   peer_caps = gst_pad_get_allowed_caps (GST_VIDEO_DECODER_SRC_PAD (base));
   GST_DEBUG_OBJECT (base, "Allowed caps %" GST_PTR_FORMAT, peer_caps);
 
@@ -475,19 +500,32 @@ gst_va_base_dec_get_preferred_format_and_caps_features (GstVaBaseDec * base,
   else
     gst_clear_caps (&peer_caps);
 
-  if (gst_caps_is_empty (preferred_caps)
-      || gst_caps_is_any (preferred_caps)) {
-    /* if any or not linked yet then system memory and nv12 */
+  if (gst_caps_is_empty (preferred_caps)) {
     if (capsfeatures)
-      *capsfeatures = NULL;
+      *capsfeatures = NULL;     /* system memory */
     if (format)
       *format = _default_video_format_from_chroma (base->rt_format);
     goto bail;
   }
 
-  features = gst_caps_get_features (preferred_caps, 0);
-  if (features && capsfeatures)
-    *capsfeatures = gst_caps_features_copy (features);
+  if (capsfeatures) {
+    features = gst_caps_get_features (preferred_caps, 0);
+    if (features) {
+      *capsfeatures = gst_caps_features_copy (features);
+
+      if (is_any
+          && !gst_caps_features_is_equal (features,
+              GST_CAPS_FEATURES_MEMORY_SYSTEM_MEMORY)
+          && !_downstream_has_video_meta (base, preferred_caps)) {
+        GST_INFO_OBJECT (base, "Downstream reports ANY caps but without"
+            " VideoMeta support; fallback to system memory.");
+        gst_caps_features_free (*capsfeatures);
+        *capsfeatures = NULL;
+      }
+    } else {
+      *capsfeatures = NULL;
+    }
+  }
 
   if (!format)
     goto bail;
-- 
2.7.4