vf_vdpaurb: deprecate this filter

DOCS/man/vf.rst

@@ -807,6 +807,8 @@ Available filters are:
             Apply high quality VDPAU scaling (needs capable hardware).
 
 ``vdpaurb``
+    This filter is deprecated. Use ``--hwdec=vdpau-copy`` instead.
+
     VDPAU video read back. Works with ``--vo=vdpau`` and ``--vo=opengl`` only.
     This filter will read back frames decoded by VDPAU so that other filters,
     which are not normally compatible with VDPAU, can be used like normal.

video/filter/vf_vdpaurb.c

@@ -87,6 +87,9 @@ static int vf_open(vf_instance_t *vf)
 {
     struct vf_priv_s *p = vf->priv;
 
+    MP_WARN(vf, "This filter is deprecated and will be removed.\n");
+    MP_WARN(vf, "Use --hwdec=vdpau-copy instead.\n");
+
     vf->filter_ext = filter_ext;
     vf->filter = NULL;
     vf->reconfig = reconfig;