Fixed in next gst-plugins-farsight release (0.12.2)

diff -rN -u old-gst-plugins-farsight/configure.ac new-gst-plugins-farsight/configure.ac
--- old-gst-plugins-farsight/configure.ac       2007-05-17 16:34:58.000000000 -0400
+++ new-gst-plugins-farsight/configure.ac       2007-05-17 16:34:59.000000000 -0400
@@ -71,6 +71,11 @@
   gstreamer-$GST_MAJORMINOR >= $GST_REQUIRED,
   HAVE_GST=yes,HAVE_GST=no)
 
+dnl check to disable G729 if we don't have 10.13 at least
+PKG_CHECK_MODULES(GST, \
+  gstreamer-$GST_MAJORMINOR >= 0.10.13,
+  HAVE_GST_13=yes,HAVE_GST_13=no)
+
 dnl Give error and exit if we don't have gstreamer
 if test "x$HAVE_GST" = "xno"; then
   AC_MSG_ERROR(you need gstreamer >= $GST_REQUIRED development packages installed !)
@@ -327,7 +332,7 @@
 AC_SUBST(HAVE_JINGLEP2P)
 AM_CONDITIONAL(USE_JINGLEP2P, test x$USE_JINGLEP2P = xyes)
 
-dnl libj2k
+dnl g729 
 AC_ARG_ENABLE([g729],
   AC_HELP_STRING([--enable-g729],
       [Compile the G729 payloader and depayloader]),
@@ -335,9 +340,11 @@
   [g729="no"])
 
 AC_MSG_RESULT(Checking for --enable-g729... $g729)
-AM_CONDITIONAL(ENABLE_G729, test "x$g729" != "xno")
-if test "x$g729" != "xno"; then
-   AC_DEFINE(ENABLE_G729, , [Compile the G729 payloader and depayloader])
+if test "x$g729" != "xno" && test "x$HAVE_GST_13" == "xyes" ; then
+  AM_CONDITIONAL(ENABLE_G729, true)
+  AC_DEFINE(ENABLE_G729, , [Compile the G729 payloader and depayloader])
+else
+  AM_CONDITIONAL(ENABLE_G729, false)
 fi