plugins: allow bufferpool to not allocate vaapi video meta.

Add GST_VAAPI_VIDEO_BUFFER_POOL_ACQUIRE_FLAG_NO_ALLOC params flag that
can be used to disable early allocations of vaapi video metas on buffers,
thus delagating that to the bufferpool user.

gst/vaapi/gstvaapivideobufferpool.c

@@ -216,21 +216,29 @@ gst_vaapi_video_buffer_pool_alloc_buffer (GstBufferPool * pool,
   GstMemory *mem;
   GstBuffer *buffer;
 
+  const gboolean alloc_vaapi_video_meta = !params ||
+      !(params->flags & GST_VAAPI_VIDEO_BUFFER_POOL_ACQUIRE_FLAG_NO_ALLOC);
+
   if (!priv->allocator)
     goto error_no_allocator;
 
+  if (alloc_vaapi_video_meta) {
     meta = gst_vaapi_video_meta_new (priv->display);
     if (!meta)
       goto error_create_meta;
 
     buffer = gst_vaapi_video_buffer_new (meta);
+  } else {
+    meta = NULL;
+    buffer = gst_vaapi_video_buffer_new_empty ();
+  }
   if (!buffer)
     goto error_create_buffer;
 
   mem = gst_vaapi_video_memory_new (priv->allocator, meta);
   if (!mem)
     goto error_create_memory;
-  gst_vaapi_video_meta_unref (meta);
+  gst_vaapi_video_meta_replace (&meta, NULL);
   gst_buffer_append_memory (buffer, mem);
 
   if (priv->has_video_meta) {

gst/vaapi/gstvaapivideobufferpool.h

@@ -69,6 +69,20 @@ typedef struct _GstVaapiVideoBufferPoolPrivate GstVaapiVideoBufferPoolPrivate;
   "GstBufferPoolOptionVideoGLTextureUploadMeta"
 #endif
 
+/**
+ * GstVaapiVideoBufferPoolAcquireFlags:
+ * @GST_VAAPI_VIDEO_BUFFER_POOL_ACQUIRE_FLAG_NO_ALLOC: option to
+ *   request that vaapi video metadata are not initially allocated,
+ *   but are subsequently provided by the user.
+ *
+ * The set of #GstVaapiVideoBufferPool specific flags for
+ * gst_buffer_pool_acquire_buffer().
+ */
+typedef enum {
+  GST_VAAPI_VIDEO_BUFFER_POOL_ACQUIRE_FLAG_NO_ALLOC =
+      GST_BUFFER_POOL_ACQUIRE_FLAG_LAST << 0,
+} GstVaapiVideoBufferPoolAcquireFlags;
+
 /**
  * GstVaapiVideoBufferPool:
  *

gst/vaapi/gstvaapivideomemory.c

@@ -281,7 +281,7 @@ gst_vaapi_video_memory_new (GstAllocator * base_allocator,
   mem->surface = NULL;
   mem->image_info = &allocator->image_info;
   mem->image = NULL;
-  mem->meta = gst_vaapi_video_meta_ref (meta);
+  mem->meta = meta ? gst_vaapi_video_meta_ref (meta) : NULL;
   mem->map_type = 0;
   mem->map_count = 0;
   mem->use_direct_rendering = allocator->has_direct_rendering;
@@ -294,7 +294,7 @@ gst_vaapi_video_memory_free (GstVaapiVideoMemory * mem)
   mem->surface = NULL;
   gst_vaapi_video_memory_reset_image (mem);
   gst_vaapi_surface_proxy_replace (&mem->proxy, NULL);
-  gst_vaapi_video_meta_unref (mem->meta);
+  gst_vaapi_video_meta_replace (&mem->meta, NULL);
   gst_object_unref (GST_MEMORY_CAST (mem)->allocator);
   g_slice_free (GstVaapiVideoMemory, mem);
 }
@@ -319,6 +319,7 @@ gst_vaapi_video_memory_reset_surface (GstVaapiVideoMemory * mem)
   mem->surface = NULL;
   gst_vaapi_video_memory_reset_image (mem);
   gst_vaapi_surface_proxy_replace (&mem->proxy, NULL);
+  if (mem->meta)
     gst_vaapi_video_meta_set_surface_proxy (mem->meta, NULL);
 }
 
@@ -328,6 +329,9 @@ gst_vaapi_video_memory_map (GstVaapiVideoMemory * mem, gsize maxsize,
 {
   gpointer data;
 
+  g_return_val_if_fail (mem, NULL);
+  g_return_val_if_fail (mem->meta, NULL);
+
   if (mem->map_count == 0) {
     switch (flags & GST_MAP_READWRITE) {
       case 0:
@@ -426,6 +430,9 @@ gst_vaapi_video_memory_copy (GstVaapiVideoMemory * mem,
   GstMemory *out_mem;
   gsize maxsize;
 
+  g_return_val_if_fail (mem, NULL);
+  g_return_val_if_fail (mem->meta, NULL);
+
   /* XXX: this implements a soft-copy, i.e. underlying VA surfaces
      are not copied */
   (void) gst_memory_get_sizes (GST_MEMORY_CAST (mem), NULL, &maxsize);