diff --git a/ChangeLog b/ChangeLog
index 782dd030a7..7e3bb2dad4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2008-02-01  Wim Taymans  <wim.taymans@collabora.co.uk>
+
+	Patch by: Thijs Vermeir <thijsvermeir at gmail dot com>
+
+	* gst-libs/gst/rtp/gstrtpbuffer.c:
+	(gst_rtp_buffer_set_extension_data):
+	* gst-libs/gst/rtp/gstrtpbuffer.h:
+	* tests/check/libs/rtp.c: (GST_START_TEST), (rtp_suite):
+	Add gst_rtp_buffer_set_extension_data() 
+	Add a unit test for this addition. Fixes #511478.
+	API: GstRTPBuffer:gst_rtp_buffer_set_extension_data()
+
 2008-01-30  Jan Schmidt  <jan.schmidt@sun.com>
 
 	* configure.ac:
diff --git a/gst-libs/gst/rtp/gstrtpbuffer.c b/gst-libs/gst/rtp/gstrtpbuffer.c
index 7284adddf8..ab207a4b0f 100644
--- a/gst-libs/gst/rtp/gstrtpbuffer.c
+++ b/gst-libs/gst/rtp/gstrtpbuffer.c
@@ -630,6 +630,51 @@ gst_rtp_buffer_get_extension_data (GstBuffer * buffer, guint16 * bits,
   return TRUE;
 }
 
+/**
+ * gst_rtp_buffer_set_extension_data:
+ * @buffer: the buffer
+ * @bits: the bits specific for the extension
+ * @length: the length that counts the number of 32-bit words in
+ * the extension, excluding the extension header ( therefore zero is a valid length)
+ *
+ * Set the extension bit of the rtp buffer and fill in the @bits and @length of the
+ * extension header. It will refuse to set the extension data if the buffer is not
+ * large enough.
+ *
+ * Returns: True if done.
+ *
+ * Since : 0.10.18
+ */
+gboolean
+gst_rtp_buffer_set_extension_data (GstBuffer * buffer, guint16 bits,
+    guint16 length)
+{
+  guint32 min_size = 0;
+  guint8 *data;
+
+  g_return_val_if_fail (GST_IS_BUFFER (buffer), FALSE);
+  g_return_val_if_fail (GST_BUFFER_DATA (buffer) != NULL, FALSE);
+
+  gst_rtp_buffer_set_extension (buffer, TRUE);
+  min_size =
+      GST_RTP_HEADER_LEN + GST_RTP_HEADER_CSRC_SIZE (buffer) + 4 +
+      length * sizeof (guint32);
+
+  if (min_size > GST_BUFFER_SIZE (buffer)) {
+    GST_WARNING_OBJECT (buffer,
+        "rtp buffer too small: need more than %d bytes but only have %d bytes",
+        min_size, GST_BUFFER_SIZE (buffer));
+    return FALSE;
+  }
+
+  data =
+      GST_BUFFER_DATA (buffer) + GST_RTP_HEADER_LEN +
+      GST_RTP_HEADER_CSRC_SIZE (buffer);
+  GST_WRITE_UINT16_BE (data, bits);
+  GST_WRITE_UINT16_BE (data + 2, length);
+  return TRUE;
+}
+
 /**
  * gst_rtp_buffer_get_ssrc:
  * @buffer: the buffer
diff --git a/gst-libs/gst/rtp/gstrtpbuffer.h b/gst-libs/gst/rtp/gstrtpbuffer.h
index dc8c2ace18..a9106e3655 100644
--- a/gst-libs/gst/rtp/gstrtpbuffer.h
+++ b/gst-libs/gst/rtp/gstrtpbuffer.h
@@ -68,6 +68,7 @@ gboolean        gst_rtp_buffer_get_extension         (GstBuffer *buffer);
 void            gst_rtp_buffer_set_extension         (GstBuffer *buffer, gboolean extension);
 gboolean        gst_rtp_buffer_get_extension_data    (GstBuffer *buffer, guint16 *bits,
                                                       gpointer *data, guint *wordlen);
+gboolean        gst_rtp_buffer_set_extension_data    (GstBuffer *buffer, guint16 bits, guint16 length);
 
 guint32         gst_rtp_buffer_get_ssrc              (GstBuffer *buffer);
 void            gst_rtp_buffer_set_ssrc              (GstBuffer *buffer, guint32 ssrc);
diff --git a/tests/check/libs/rtp.c b/tests/check/libs/rtp.c
index 82423d55e5..757f00b3de 100644
--- a/tests/check/libs/rtp.c
+++ b/tests/check/libs/rtp.c
@@ -106,6 +106,49 @@ GST_START_TEST (test_rtp_buffer)
 
 GST_END_TEST;
 
+GST_START_TEST (test_rtp_buffer_set_extension_data)
+{
+  GstBuffer *buf;
+  guint8 *data;
+  guint16 bits;
+  guint size;
+  gpointer pointer;
+
+  /* check GstRTPHeader structure alignment and packing */
+  buf = gst_rtp_buffer_new_allocate (4, 0, 0);
+  data = GST_BUFFER_DATA (buf);
+
+  /* should be impossible to set the extension data */
+  fail_unless (gst_rtp_buffer_set_extension_data (buf, 0, 4) == FALSE);
+  fail_unless (gst_rtp_buffer_get_extension (buf) == TRUE);
+
+  /* should be possible to set the extension data */
+  fail_unless (gst_rtp_buffer_set_extension_data (buf, 270, 0) == TRUE);
+  fail_unless (gst_rtp_buffer_get_extension (buf) == TRUE);
+  gst_rtp_buffer_get_extension_data (buf, &bits, &pointer, &size);
+  fail_unless (bits == 270);
+  fail_unless (size == 0);
+  fail_unless (pointer == GST_BUFFER_DATA (buf) + 16);
+  pointer = gst_rtp_buffer_get_payload (buf);
+  fail_unless (pointer == GST_BUFFER_DATA (buf) + 16);
+  gst_buffer_unref (buf);
+
+  buf = gst_rtp_buffer_new_allocate (20, 0, 0);
+  data = GST_BUFFER_DATA (buf);
+  fail_unless (gst_rtp_buffer_get_extension (buf) == FALSE);
+  fail_unless (gst_rtp_buffer_set_extension_data (buf, 333, 2) == TRUE);
+  fail_unless (gst_rtp_buffer_get_extension (buf) == TRUE);
+  gst_rtp_buffer_get_extension_data (buf, &bits, &pointer, &size);
+  fail_unless (bits == 333);
+  fail_unless (size == 2);
+  fail_unless (pointer == GST_BUFFER_DATA (buf) + 16);
+  pointer = gst_rtp_buffer_get_payload (buf);
+  fail_unless (pointer == GST_BUFFER_DATA (buf) + 24);
+  gst_buffer_unref (buf);
+}
+
+GST_END_TEST;
+
 static Suite *
 rtp_suite (void)
 {
@@ -114,6 +157,7 @@ rtp_suite (void)
 
   suite_add_tcase (s, tc_chain);
   tcase_add_test (tc_chain, test_rtp_buffer);
+  tcase_add_test (tc_chain, test_rtp_buffer_set_extension_data);
   return s;
 }