diff --git a/gst/vaapi/gstvaapidecode.c b/gst/vaapi/gstvaapidecode.c
index 545a604be9..b1f4bc5f4e 100644
--- a/gst/vaapi/gstvaapidecode.c
+++ b/gst/vaapi/gstvaapidecode.c
@@ -88,11 +88,36 @@ static GstStaticPadTemplate gst_vaapidecode_src_factory =
         GST_PAD_ALWAYS,
         GST_STATIC_CAPS(gst_vaapidecode_src_caps_str));
 
-static void
-gst_vaapidecode_implements_iface_init(GstImplementsInterfaceClass *iface);
+/* GstImplementsInterface interface */
+static gboolean
+gst_vaapidecode_implements_interface_supported(
+    GstImplementsInterface *iface,
+    GType                   type
+)
+{
+    return (type == GST_TYPE_VIDEO_CONTEXT);
+}
 
 static void
-gst_video_context_interface_init(GstVideoContextInterface *iface);
+gst_vaapidecode_implements_iface_init(GstImplementsInterfaceClass *iface)
+{
+    iface->supported = gst_vaapidecode_implements_interface_supported;
+}
+
+/* GstVideoContext interface */
+static void
+gst_vaapidecode_set_video_context(GstVideoContext *context, const gchar *type,
+    const GValue *value)
+{
+    GstVaapiDecode *decode = GST_VAAPIDECODE (context);
+    gst_vaapi_set_display (type, value, &decode->display);
+}
+
+static void
+gst_video_context_interface_init(GstVideoContextInterface *iface)
+{
+    iface->set_context = gst_vaapidecode_set_video_context;
+}
 
 #define GstVideoContextClass GstVideoContextInterface
 G_DEFINE_TYPE_WITH_CODE(
@@ -417,39 +442,6 @@ gst_vaapidecode_reset_full(GstVaapiDecode *decode, GstCaps *caps, gboolean hard)
     return gst_vaapidecode_create(decode, caps);
 }
 
-/* GstImplementsInterface interface */
-
-static gboolean
-gst_vaapidecode_implements_interface_supported(
-    GstImplementsInterface *iface,
-    GType                   type
-)
-{
-    return (type == GST_TYPE_VIDEO_CONTEXT);
-}
-
-static void
-gst_vaapidecode_implements_iface_init(GstImplementsInterfaceClass *iface)
-{
-    iface->supported = gst_vaapidecode_implements_interface_supported;
-}
-
-/* GstVideoContext interface */
-
-static void
-gst_vaapidecode_set_video_context(GstVideoContext *context, const gchar *type,
-    const GValue *value)
-{
-    GstVaapiDecode *decode = GST_VAAPIDECODE (context);
-    gst_vaapi_set_display (type, value, &decode->display);
-}
-
-static void
-gst_video_context_interface_init(GstVideoContextInterface *iface)
-{
-    iface->set_context = gst_vaapidecode_set_video_context;
-}
-
 static void
 gst_vaapidecode_finalize(GObject *object)
 {
diff --git a/gst/vaapi/gstvaapidownload.c b/gst/vaapi/gstvaapidownload.c
index 4d1d49fef8..5a29501fc1 100644
--- a/gst/vaapi/gstvaapidownload.c
+++ b/gst/vaapi/gstvaapidownload.c
@@ -99,11 +99,36 @@ struct _GstVaapiDownloadClass {
     GstBaseTransformClass parent_class;
 };
 
-static void
-gst_vaapidownload_implements_iface_init(GstImplementsInterfaceClass *iface);
+/* GstImplementsInterface interface */
+static gboolean
+gst_vaapidownload_implements_interface_supported(
+    GstImplementsInterface *iface,
+    GType                   type
+)
+{
+    return (type == GST_TYPE_VIDEO_CONTEXT);
+}
 
 static void
-gst_video_context_interface_init(GstVideoContextInterface *iface);
+gst_vaapidownload_implements_iface_init(GstImplementsInterfaceClass *iface)
+{
+    iface->supported = gst_vaapidownload_implements_interface_supported;
+}
+
+/* GstVideoContext interface */
+static void
+gst_vaapidownload_set_video_context(GstVideoContext *context, const gchar *type,
+    const GValue *value)
+{
+  GstVaapiDownload *download = GST_VAAPIDOWNLOAD (context);
+  gst_vaapi_set_display (type, value, &download->display);
+}
+
+static void
+gst_video_context_interface_init(GstVideoContextInterface *iface)
+{
+    iface->set_context = gst_vaapidownload_set_video_context;
+}
 
 #define GstVideoContextClass GstVideoContextInterface
 G_DEFINE_TYPE_WITH_CODE(
@@ -161,39 +186,6 @@ gst_vaapidownload_query(
     GstQuery *query
 );
 
-/* GstImplementsInterface interface */
-
-static gboolean
-gst_vaapidownload_implements_interface_supported(
-    GstImplementsInterface *iface,
-    GType                   type
-)
-{
-    return (type == GST_TYPE_VIDEO_CONTEXT);
-}
-
-static void
-gst_vaapidownload_implements_iface_init(GstImplementsInterfaceClass *iface)
-{
-    iface->supported = gst_vaapidownload_implements_interface_supported;
-}
-
-/* GstVideoContext interface */
-
-static void
-gst_vaapidownload_set_video_context(GstVideoContext *context, const gchar *type,
-    const GValue *value)
-{
-  GstVaapiDownload *download = GST_VAAPIDOWNLOAD (context);
-  gst_vaapi_set_display (type, value, &download->display);
-}
-
-static void
-gst_video_context_interface_init(GstVideoContextInterface *iface)
-{
-    iface->set_context = gst_vaapidownload_set_video_context;
-}
-
 static void
 gst_vaapidownload_destroy(GstVaapiDownload *download)
 {
diff --git a/gst/vaapi/gstvaapipostproc.c b/gst/vaapi/gstvaapipostproc.c
index a40352f744..3172482005 100644
--- a/gst/vaapi/gstvaapipostproc.c
+++ b/gst/vaapi/gstvaapipostproc.c
@@ -74,11 +74,40 @@ static GstStaticPadTemplate gst_vaapipostproc_src_factory =
         GST_PAD_ALWAYS,
         GST_STATIC_CAPS(gst_vaapipostproc_src_caps_str));
 
-static void
-gst_vaapipostproc_implements_iface_init(GstImplementsInterfaceClass *iface);
+/* GstImplementsInterface interface */
+static gboolean
+gst_vaapipostproc_implements_interface_supported(
+    GstImplementsInterface *iface,
+    GType                   type
+)
+{
+    return (type == GST_TYPE_VIDEO_CONTEXT);
+}
 
 static void
-gst_video_context_interface_init(GstVideoContextInterface *iface);
+gst_vaapipostproc_implements_iface_init(GstImplementsInterfaceClass *iface)
+{
+    iface->supported = gst_vaapipostproc_implements_interface_supported;
+}
+
+/* GstVideoContext interface */
+static void
+gst_vaapipostproc_set_video_context(
+    GstVideoContext *context,
+    const gchar     *type,
+    const GValue    *value
+)
+{
+    GstVaapiPostproc * const postproc = GST_VAAPIPOSTPROC(context);
+
+    gst_vaapi_set_display(type, value, &postproc->display);
+}
+
+static void
+gst_video_context_interface_init(GstVideoContextInterface *iface)
+{
+    iface->set_context = gst_vaapipostproc_set_video_context;
+}
 
 #define GstVideoContextClass GstVideoContextInterface
 G_DEFINE_TYPE_WITH_CODE(
@@ -161,43 +190,6 @@ get_vaapipostproc_from_pad(GstPad *pad)
     return GST_VAAPIPOSTPROC(gst_pad_get_parent_element(pad));
 }
 
-/* GstImplementsInterface interface */
-
-static gboolean
-gst_vaapipostproc_implements_interface_supported(
-    GstImplementsInterface *iface,
-    GType                   type
-)
-{
-    return (type == GST_TYPE_VIDEO_CONTEXT);
-}
-
-static void
-gst_vaapipostproc_implements_iface_init(GstImplementsInterfaceClass *iface)
-{
-    iface->supported = gst_vaapipostproc_implements_interface_supported;
-}
-
-/* GstVideoContext interface */
-
-static void
-gst_vaapipostproc_set_video_context(
-    GstVideoContext *context,
-    const gchar     *type,
-    const GValue    *value
-)
-{
-    GstVaapiPostproc * const postproc = GST_VAAPIPOSTPROC(context);
-
-    gst_vaapi_set_display(type, value, &postproc->display);
-}
-
-static void
-gst_video_context_interface_init(GstVideoContextInterface *iface)
-{
-    iface->set_context = gst_vaapipostproc_set_video_context;
-}
-
 static inline gboolean
 gst_vaapipostproc_ensure_display(GstVaapiPostproc *postproc)
 {
diff --git a/gst/vaapi/gstvaapisink.c b/gst/vaapi/gstvaapisink.c
index 5d41d05c5e..90350dec5a 100644
--- a/gst/vaapi/gstvaapisink.c
+++ b/gst/vaapi/gstvaapisink.c
@@ -85,11 +85,37 @@ static GstStaticPadTemplate gst_vaapisink_sink_factory =
         GST_PAD_ALWAYS,
         GST_STATIC_CAPS(gst_vaapisink_sink_caps_str));
 
-static void
-gst_vaapisink_implements_iface_init(GstImplementsInterfaceClass *iface);
+/* GstImplementsInterface interface */
+static gboolean
+gst_vaapisink_implements_interface_supported(
+    GstImplementsInterface *iface,
+    GType                   type
+)
+{
+    return (type == GST_TYPE_VIDEO_CONTEXT ||
+            type == GST_TYPE_X_OVERLAY);
+}
 
 static void
-gst_vaapisink_video_context_iface_init(GstVideoContextInterface *iface);
+gst_vaapisink_implements_iface_init(GstImplementsInterfaceClass *iface)
+{
+    iface->supported = gst_vaapisink_implements_interface_supported;
+}
+
+/* GstVideoContext interface */
+static void
+gst_vaapisink_set_video_context(GstVideoContext *context, const gchar *type,
+    const GValue *value)
+{
+  GstVaapiSink *sink = GST_VAAPISINK (context);
+  gst_vaapi_set_display (type, value, &sink->display);
+}
+
+static void
+gst_vaapisink_video_context_iface_init(GstVideoContextInterface *iface)
+{
+    iface->set_context = gst_vaapisink_set_video_context;
+}
 
 static void
 gst_vaapisink_xoverlay_iface_init(GstXOverlayClass *iface);
@@ -118,40 +144,6 @@ enum {
 #define DEFAULT_DISPLAY_TYPE            GST_VAAPI_DISPLAY_TYPE_ANY
 #define DEFAULT_ROTATION                GST_VAAPI_ROTATION_0
 
-/* GstImplementsInterface interface */
-
-static gboolean
-gst_vaapisink_implements_interface_supported(
-    GstImplementsInterface *iface,
-    GType                   type
-)
-{
-    return (type == GST_TYPE_VIDEO_CONTEXT ||
-            type == GST_TYPE_X_OVERLAY);
-}
-
-static void
-gst_vaapisink_implements_iface_init(GstImplementsInterfaceClass *iface)
-{
-    iface->supported = gst_vaapisink_implements_interface_supported;
-}
-
-/* GstVideoContext interface */
-
-static void
-gst_vaapisink_set_video_context(GstVideoContext *context, const gchar *type,
-    const GValue *value)
-{
-  GstVaapiSink *sink = GST_VAAPISINK (context);
-  gst_vaapi_set_display (type, value, &sink->display);
-}
-
-static void
-gst_vaapisink_video_context_iface_init(GstVideoContextInterface *iface)
-{
-    iface->set_context = gst_vaapisink_set_video_context;
-}
-
 /* GstXOverlay interface */
 
 #if USE_X11
diff --git a/gst/vaapi/gstvaapiupload.c b/gst/vaapi/gstvaapiupload.c
index 6118454634..05941d555c 100644
--- a/gst/vaapi/gstvaapiupload.c
+++ b/gst/vaapi/gstvaapiupload.c
@@ -75,11 +75,41 @@ static GstStaticPadTemplate gst_vaapiupload_src_factory =
         GST_PAD_ALWAYS,
         GST_STATIC_CAPS(gst_vaapiupload_vaapi_caps_str));
 
-static void
-gst_vaapiupload_implements_iface_init(GstImplementsInterfaceClass *iface);
+
+/* GstImplementsInterface interface */
+static gboolean
+gst_vaapiupload_implements_interface_supported(
+    GstImplementsInterface *iface,
+    GType                   type
+)
+{
+    return (type == GST_TYPE_VIDEO_CONTEXT);
+}
 
 static void
-gst_video_context_interface_init(GstVideoContextInterface *iface);
+gst_vaapiupload_implements_iface_init(GstImplementsInterfaceClass *iface)
+{
+    iface->supported = gst_vaapiupload_implements_interface_supported;
+}
+
+/* GstVideoContext interface */
+static void
+gst_vaapiupload_set_video_context(GstVideoContext *context, const gchar *type,
+    const GValue *value)
+{
+    GstVaapiUpload * const upload = GST_VAAPIUPLOAD(context);
+
+    gst_vaapi_set_display(type, value, &upload->display);
+
+    if (upload->uploader)
+        gst_vaapi_uploader_ensure_display(upload->uploader, upload->display);
+}
+
+static void
+gst_video_context_interface_init(GstVideoContextInterface *iface)
+{
+    iface->set_context = gst_vaapiupload_set_video_context;
+}
 
 #define GstVideoContextClass GstVideoContextInterface
 G_DEFINE_TYPE_WITH_CODE(
@@ -149,43 +179,6 @@ gst_vaapiupload_query(
     GstQuery *query
 );
 
-/* GstImplementsInterface interface */
-
-static gboolean
-gst_vaapiupload_implements_interface_supported(
-    GstImplementsInterface *iface,
-    GType                   type
-)
-{
-    return (type == GST_TYPE_VIDEO_CONTEXT);
-}
-
-static void
-gst_vaapiupload_implements_iface_init(GstImplementsInterfaceClass *iface)
-{
-    iface->supported = gst_vaapiupload_implements_interface_supported;
-}
-
-/* GstVideoContext interface */
-
-static void
-gst_vaapiupload_set_video_context(GstVideoContext *context, const gchar *type,
-    const GValue *value)
-{
-    GstVaapiUpload * const upload = GST_VAAPIUPLOAD(context);
-
-    gst_vaapi_set_display(type, value, &upload->display);
-
-    if (upload->uploader)
-        gst_vaapi_uploader_ensure_display(upload->uploader, upload->display);
-}
-
-static void
-gst_video_context_interface_init(GstVideoContextInterface *iface)
-{
-    iface->set_context = gst_vaapiupload_set_video_context;
-}
-
 static void
 gst_vaapiupload_destroy(GstVaapiUpload *upload)
 {