diff --git a/Makefile.am b/Makefile.am
index 90a6343..872ca5e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -9,7 +9,13 @@ else
 ORTP_DIR = oRTP
 endif
 
-SUBDIRS = m4 pixmaps po ipkg $(ORTP_DIR) gsmlib mediastreamer2\
+if EXTERNAL_GSM
+GSM_DIR =
+else
+GSM_DIR = gsmlib
+endif
+
+SUBDIRS = m4 pixmaps po ipkg $(ORTP_DIR) $(GSM_DIR) mediastreamer2\
 		media_api exosip coreapi console gtk share
 
 
diff --git a/configure.in b/configure.in
index 5c55410..81e917c 100644
--- a/configure.in
+++ b/configure.in
@@ -320,6 +320,30 @@ AC_SUBST(ORTP_LIBS)
 
 AM_CONDITIONAL(EXTERNAL_ORTP, [test "$external_ortp" = 'true'])
 
+AC_ARG_WITH(gsm,
+         AS_HELP_STRING([--with-gsm],[Sets the installation prefix of GSM codec library (default=/usr)]),
+	 [ gsmdir=${withval}],[ gsmdir=/usr ])
+
+AC_ARG_ENABLE(external-gsm,
+      AS_HELP_STRING([--enable-external-gsm],[Use external GSM library (default=false)]),
+      [case "${enableval}" in
+        yes) external_gsm=true ;;
+        no)  external_gsm=false ;;
+        *) AC_MSG_ERROR(bad value ${enableval} for --enable-external-gsm) ;;
+      esac],[external_gsm=false])
+
+if test "$external_gsm" = 'true'; then
+	LP_CHECK_GSM
+else
+	AC_CONFIG_SUBDIRS(gsmlib)
+	GSM_CFLAGS="-I\$(top_srcdir)/gsmlib"
+	GSM_LIBS="\$(top_builddir)/gsmlib/libgsm.la"
+	AC_SUBST(GSM_CFLAGS)
+	AC_SUBST(GSM_LIBS)
+fi
+
+AM_CONDITIONAL(EXTERNAL_GSM, [test "$external_gsm" = 'true'])
+
 dnl Packaging: Pick oRTP version from ${top_srcdir}/oRTP/configure.ac
 dnl Feel free to propose an alternative & cleaner version...
 top_srcdir=`dirname $0`
diff --git a/m4/gsm.m4 b/m4/gsm.m4
new file mode 100644
index 0000000..b75a747
--- /dev/null
+++ b/m4/gsm.m4
@@ -0,0 +1,29 @@
+AC_DEFUN([LP_CHECK_GSM],[
+
+gsm_pkgconfig=true
+
+PKG_CHECK_MODULES([GSM], [gsm], , [gsm_pkgconfig=false])
+
+if test $gsm_pkgconfig = false; then
+	if test "${gsmdir}" != "/usr"; then
+		CFLAGS_save="$CFLAGS"
+		CFLAGS="$CFLAGS -I${gsmdir}/include"
+	fi
+	AC_CHECK_HEADER([gsm/gsm.h], , AC_MSG_ERROR([Could not find GSM headers !]))
+	if test "${gsmdir}" != "/usr"; then
+		GSM_CFLAGS="-I${gsmdir}/include"
+		CFLAGS="$CFLAGS_save"
+		LIBS_save="$LIBS"
+		LIBS="$LIBS -L${gsmdir}/lib"
+	fi
+	AC_CHECK_LIB([gsm], [gsm_create], , AC_MSG_ERROR([Could not find GSM library]))
+	if test "${gsmdir}" != "/usr"; then
+		GSM_LIBS="-L${gsmdir}/lib -lgsm"
+		LIBS="$LIBS_save"
+	else
+		GSM_LIBS="-lgsm"
+	fi
+fi
+AC_SUBST([GSM_LIBS])
+AC_SUBST([GSM_CFLAGS])
+])
diff --git a/mediastreamer2/autogen.sh b/mediastreamer2/autogen.sh
index 64516e8..fb71734 100755
--- a/mediastreamer2/autogen.sh
+++ b/mediastreamer2/autogen.sh
@@ -14,6 +14,6 @@ echo "Generating build scripts in mediastreamer..."
 set -x
 libtoolize --copy --force
 autoheader
-$ACLOCAL 
+$ACLOCAL -I m4
 $AUTOMAKE --force-missing --add-missing --copy
 autoconf
diff --git a/mediastreamer2/configure.ac b/mediastreamer2/configure.ac
index 89d66fa..9621a5e 100644
--- a/mediastreamer2/configure.ac
+++ b/mediastreamer2/configure.ac
@@ -263,31 +263,40 @@ AC_SUBST(SPEEX_LIBS)
 AM_CONDITIONAL(BUILD_SPEEX, test x$build_speex = xyes )
 
 dnl check for gsm
-AC_ARG_WITH( gsm,
-		  [  --with-gsm		Sets the installation prefix of gsm codec library [default=/usr] ],
-		  [ gsmdir=${withval}],[ gsmdir=/usr ])
-if test -e ../gsmlib/gsm.h ; then 
-	echo "building from linphone source tree, using ../gsmlib/gsm.h"
-	GSM_CFLAGS="-I\$(top_srcdir)/../gsmlib"
-	GSM_LIBS="\$(top_builddir)/../gsmlib/libgsm.la"
-	build_gsm=yes
-	AC_SUBST(GSM_CFLAGS)
-	AC_SUBST(GSM_LIBS)
-else
-	MS_CHECK_DEP([gsm codec],[GSM],[${gsmdir}/include],
-		[${gsmdir}/lib],[gsm.h],[gsm],[gsm_create])
-
-	if test "$GSM_found" = "yes" ; then
-	   build_gsm=yes
+AC_ARG_WITH(gsm,
+	AS_HELP_STRING([--with-gsm],[Sets the installation prefix of gsm codec library (default=/usr)]),
+	[ gsmdir=${withval}],[ gsmdir=/usr ])
+AC_ARG_ENABLE(external-gsm,
+	AS_HELP_STRING([--enable-external-gsm],[Use external GSM library]),
+	[case "${enableval}" in
+	      yes) external_gsm=true ;;
+	      no)  external_gsm=false ;;
+	      *) AC_MSG_ERROR(bad value ${enableval} for --enable-external-gsm) ;;
+	 esac],[external_gsm=false])
+
+if test "$external_gsm" = 'false'; then
+	if test -e $srcdir/../gsmlib/gsm.h ; then 
+		echo "building from linphone source tree, using ../gsmlib/gsm.h"
+		GSM_CFLAGS="-I\$(top_srcdir)/../gsmlib"
+		GSM_LIBS="\$(top_builddir)/../gsmlib/libgsm.la"
+		AC_SUBST(GSM_CFLAGS)
+		AC_SUBST(GSM_LIBS)
+		build_gsm=yes
+	else
+		external_gsm=true
 	fi
 fi
+if test "$external_gsm" = 'true'; then
+	MS_CHECK_GSM
+	build_gsm=yes
+fi
+
+AM_CONDITIONAL(BUILD_GSM, test x$build_gsm = xyes )
 
 build_resample=false
 AC_CHECK_LIB(resample,resample_open,[LIBS="$LIBS -lresample"; build_resample=yes])
 AM_CONDITIONAL(BUILD_RESAMPLE, test x$build_resample = xyes )
 
-AM_CONDITIONAL(BUILD_GSM, test x$build_gsm = xyes )
-
 MS_CHECK_VIDEO
 AM_CONDITIONAL(BUILD_VIDEO, test "$video" = "true")
 AM_CONDITIONAL(BUILD_THEORA, test "$have_theora" = "yes")
diff --git a/mediastreamer2/m4/gsm.m4 b/mediastreamer2/m4/gsm.m4
new file mode 100644
index 0000000..2208955
--- /dev/null
+++ b/mediastreamer2/m4/gsm.m4
@@ -0,0 +1,29 @@
+AC_DEFUN([MS_CHECK_GSM],[
+
+gsm_pkgconfig=true
+
+PKG_CHECK_MODULES([GSM], [gsm], , [gsm_pkgconfig=false])
+
+if test $gsm_pkgconfig = false; then
+	if test "${gsmdir}" != "/usr"; then
+		CFLAGS_save="$CFLAGS"
+		CFLAGS="$CFLAGS -I${gsmdir}/include"
+	fi
+	AC_CHECK_HEADER([gsm/gsm.h], , AC_MSG_ERROR([Could not find GSM headers !]))
+	if test "${gsmdir}" != "/usr"; then
+		GSM_CFLAGS="-I${gsmdir}/include"
+		CFLAGS="$CFLAGS_save"
+		LIBS_save="$LIBS"
+		LIBS="$LIBS -L${gsmdir}/lib"
+	fi
+	AC_CHECK_LIB([gsm], [gsm_create], , AC_MSG_ERROR([Could not find GSM library]))
+	if test "${gsmdir}" != "/usr"; then
+		GSM_LIBS="-L${gsmdir}/lib -lgsm"
+		LIBS="$LIBS_save"
+	else
+		GSM_LIBS="-lgsm"
+	fi
+fi
+AC_SUBST([GSM_LIBS])
+AC_SUBST([GSM_CFLAGS])
+])
diff --git a/mediastreamer2/mediastreamer-config.h.in b/mediastreamer2/mediastreamer-config.h.in
index 3054af5..fb22c79 100644
--- a/mediastreamer2/mediastreamer-config.h.in
+++ b/mediastreamer2/mediastreamer-config.h.in
@@ -18,6 +18,9 @@
 /* Define to 1 if you have the `avcodec' library (-lavcodec). */
 #undef HAVE_LIBAVCODEC
 
+/* Define to 1 if you have the `gsm' library (-lgsm). */
+#undef HAVE_LIBGSM
+
 /* Define to 1 if you have the <linux/videodev2.h> header file. */
 #undef HAVE_LINUX_VIDEODEV2_H