va: filter: Add gst_va_filter_add_deinterlace_buffer()

This function decorates gst_va_filter_add_filter_buffer() to get the
number of past and future frames to hold, given the method.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2495>

sys/va/gstvafilter.c

@@ -1374,6 +1374,48 @@ _query_pipeline_caps (GstVaFilter * self, GArray * filters,
   return TRUE;
 }
 
+gboolean
+gst_va_filter_add_deinterlace_buffer (GstVaFilter * self,
+    VAProcDeinterlacingType method, guint32 * forward, guint32 * backward)
+{
+  GArray *filters = NULL;
+  VAProcFilterParameterBufferDeinterlacing params = {
+    .type = VAProcFilterDeinterlacing,
+    .algorithm = method,
+  };
+  VAProcPipelineCaps pipeline_caps = { 0, };
+  gboolean ret;
+
+  g_return_val_if_fail (GST_IS_VA_FILTER (self), FALSE);
+
+  if (!gst_va_filter_is_open (self))
+    return FALSE;
+
+  if (!(method != VAProcDeinterlacingNone
+          && method != VAProcDeinterlacingCount))
+    return FALSE;
+
+  if (!gst_va_filter_add_filter_buffer (self, &params, sizeof (params), 1))
+    return FALSE;
+
+  GST_OBJECT_LOCK (self);
+  if (self->filters)
+    filters = g_array_ref (self->filters);
+  GST_OBJECT_UNLOCK (self);
+  ret = _query_pipeline_caps (self, filters, &pipeline_caps);
+  if (filters)
+    g_array_unref (filters);
+  if (!ret)
+    return FALSE;
+
+  if (forward)
+    *forward = pipeline_caps.num_forward_references;
+  if (backward)
+    *backward = pipeline_caps.num_backward_references;
+
+  return TRUE;
+}
+
 gboolean
 gst_va_filter_add_filter_buffer (GstVaFilter * self, gpointer data, gsize size,
     guint num)

sys/va/gstvafilter.h

@@ -95,6 +95,10 @@ gboolean              gst_va_filter_add_filter_buffer     (GstVaFilter * self,
                                                            gpointer data,
                                                            gsize size,
                                                            guint num);
+gboolean              gst_va_filter_add_deinterlace_buffer(GstVaFilter * self,
+                                                           VAProcDeinterlacingType method,
+                                                           guint32 * forward,
+                                                           guint32 * backward);
 gboolean              gst_va_filter_drop_filter_buffers   (GstVaFilter * self);
 gboolean              gst_va_filter_process               (GstVaFilter * self,
                                                            GstVaSample * src,