diff --git a/prepare.py b/prepare.py
index 54fa4bfd5..b2e8decb4 100755
--- a/prepare.py
+++ b/prepare.py
@@ -47,6 +47,8 @@ class DesktopTarget(prepare.Target):
         if platform.system() == 'Windows':
             current_path = current_path.replace('\\', '/')
         self.config_file = 'configs/config-desktop.cmake'
+        if platform.system() == 'Windows':
+            self.generator = 'Visual Studio 12 2013'
         self.additional_args = [
             '-DCMAKE_INSTALL_MESSAGE=LAZY',
             '-DLINPHONE_BUILDER_EXTERNAL_SOURCE_PATH=' +
@@ -162,7 +164,7 @@ def main(argv=None):
     argparser.add_argument(
         '-f', '--force', help="Force preparation, even if working directory already exist.", action='store_true')
     argparser.add_argument(
-        '-G', '--generator', help="CMake build system generator (default: Unix Makefiles, use cmake -h to get the complete list).", default='Unix Makefiles', dest='generator')
+        '-G', '--generator', help="CMake build system generator (default: let CMake choose, use cmake -h to get the complete list).", default=None, dest='generator')
     argparser.add_argument(
         '-L', '--list-cmake-variables', help="List non-advanced CMake cache variables.", action='store_true', dest='list_cmake_variables')
     argparser.add_argument(
@@ -178,7 +180,6 @@ def main(argv=None):
 
     args, additional_args = argparser.parse_known_args()
 
-    additional_args += ["-G", args.generator]
     additional_args += ["-DLINPHONE_BUILDER_GROUP_EXTERNAL_SOURCE_PATH_BUILDERS=YES"]
 
     if args.only_submodules:
@@ -193,14 +194,14 @@ def main(argv=None):
                             "-DENABLE_H263P=YES",
                             "-DENABLE_ILBC=YES",
                             "-DENABLE_ISAC=YES",
-                            "-DENABLE_MKV=YES",
                             "-DENABLE_MPEG4=YES",
-                            "-DENABLE_OPENH264=YES"
+                            "-DENABLE_OPENH264=YES",
                             "-DENABLE_SILK=YES"]
 
     if args.package:
-        additional_args += ["-DENABLE_PACKAGING=YES"
-                            "-DENABLE_RELATIVE_PREFIX=YES"]
+        additional_args += ["-DENABLE_PACKAGING=YES"]
+        if platform.system() != 'Windows':
+            additional_args += ["-DENABLE_RELATIVE_PREFIX=YES"] # Already forced in all cases on Windows platform
     if check_tools() != 0:
         return 1
 
@@ -225,6 +226,12 @@ def main(argv=None):
         target = PythonRaspberryTarget()
     else:
         target = DesktopTarget()
+    if args.generator is not None:
+        target.generator = args.generator
+    if target.generator is None:
+        # Default to "Unix Makefiles" if no target specific generator is set and the user has not defined one
+        target.generator = "Unix Makefiles"
+
     if args.clean or args.veryclean:
         if args.veryclean:
             target.veryclean()
@@ -240,18 +247,18 @@ def main(argv=None):
                 retcode = 0
             return retcode
         # only generated makefile if we are using Ninja or Makefile
-        if args.generator.endswith('Ninja'):
+        if target.generator.endswith('Ninja'):
             if not check_is_installed("ninja", "it"):
                 return 1
             generate_makefile('ninja -C')
             info("You can now run 'make' to build.")
-        elif args.generator.endswith("Unix Makefiles"):
+        elif target.generator.endswith("Unix Makefiles"):
             generate_makefile('$(MAKE) -C')
             info("You can now run 'make' to build.")
-        elif args.generator == "Xcode":
+        elif target.generator == "Xcode":
             info("You can now open Xcode project with: open WORK/cmake/Project.xcodeproj")
         else:
-            warning("Not generating meta-makefile for generator {}.".format(args.generator))
+            warning("Not generating meta-makefile for generator {}.".format(target.generator))
 
     return 0
 
diff --git a/submodules/belle-sip b/submodules/belle-sip
index bb8d52bef..9e0cd4a73 160000
--- a/submodules/belle-sip
+++ b/submodules/belle-sip
@@ -1 +1 @@
-Subproject commit bb8d52befd3b65fc06bfdcffac1dac7079c8c964
+Subproject commit 9e0cd4a739acf16a55cd3f6f54d99d7748e5c7be
diff --git a/submodules/cmake-builder b/submodules/cmake-builder
index 511422d7e..ce4fd715c 160000
--- a/submodules/cmake-builder
+++ b/submodules/cmake-builder
@@ -1 +1 @@
-Subproject commit 511422d7e76c3b31a08535f80670ac189206b569
+Subproject commit ce4fd715cca79c20cb00b9e94bbdef2f7c3b85c8
diff --git a/submodules/mswasapi b/submodules/mswasapi
index 1adae8780..cf04af555 160000
--- a/submodules/mswasapi
+++ b/submodules/mswasapi
@@ -1 +1 @@
-Subproject commit 1adae8780c22b38a48bd5948ba0fbf88d1e7f8f0
+Subproject commit cf04af5559222eac11aa4f4a1979ce4ce39cca90
diff --git a/submodules/mswebrtc b/submodules/mswebrtc
index 9f7b3128b..27680f2d9 160000
--- a/submodules/mswebrtc
+++ b/submodules/mswebrtc
@@ -1 +1 @@
-Subproject commit 9f7b3128b9c6b396c89d784ba5ddfa68be05607a
+Subproject commit 27680f2d99e6f431d8fcc433c4120ddf48263578