build: Fix maintainer-mode and embedded FFmpeg configuration parameters

Don't use AC_CONFIG_SUBDIRS to call the FFmpeg configure script, as it
complains about all the unknown parameters autoconf gives it, and fiddling
with ac_configure_args makes maintainer-mode call our real configure script
with a bunch of bogus arguments.

Instead, use AC_CONFIG_COMMANDS to call the FFmpeg configure script
ourselves.

Remove autogen.sh code that modifies the FFmpeg configure script, as it's
not needed now that we only pass it arguments it understands, and move
the detection of flags like --disable-ffmpeg into the configure script,
otherwise they never get passed to FFmpeg if we call configure ourselves,
such as from a tarball.

autogen.sh

@@ -54,25 +54,6 @@ then
     ln -s ../../common/hooks/pre-commit.hook .git/hooks/pre-commit
 fi
 
-
-# Let's check if we can disable the building of the ffmpeg binary
-can_disable=`$FFMPEG_CO_DIR/configure --help | grep 'disable-ffmpeg' | wc -l`
-
-if [ $can_disable != "0" ]
-then
-    CONFIGURE_DEF_OPT="--disable-ffmpeg"
-fi
-
-# Let's clear the 'exit 1' command when we post an Unknown option
-echo "Patching ffmpeg ./configure"
-sed -e '/Unknown option/ {
-N
-N
-s/exit 1/#/
-}' $FFMPEG_CO_DIR/configure > $FFMPEG_CO_DIR/configure.tmp
-mv $FFMPEG_CO_DIR/configure.tmp $FFMPEG_CO_DIR/configure
-chmod +x $FFMPEG_CO_DIR/configure
-
 autogen_options $@
 
 echo -n "+ check for build tools"

configure.ac

@@ -302,12 +302,15 @@ else
       [extra configure options for internal ffmpeg ./configure script]),,
       with_ffmpeg_extra_configure=no)
 
+  # basic arguments
+  embffmpeg_configure_args="--prefix=$prefix"
+
   # Enable shared and static so that we get .a files, but with PIC code.
-  ac_configure_args="$ac_configure_args --disable-vhook --disable-ffserver --disable-ffplay --enable-postproc --enable-swscale --enable-gpl --enable-static --enable-shared --disable-encoder=flac --disable-decoder=cavs --disable-protocols --disable-devices --disable-network"
+  embffmpeg_configure_args="$embffmpeg_configure_args --disable-ffserver --disable-ffplay --enable-postproc --enable-gpl --enable-static --enable-shared --disable-encoder=flac --disable-decoder=cavs --disable-protocols --disable-devices --disable-network"
 
   # if we are cross-compiling, tell ffmpeg so
   if test "x$cross_compiling" = xyes; then
-    ac_configure_args="$ac_configure_args --enable-cross-compile \
+    embffmpeg_configure_args="$embffmpeg_configure_args --enable-cross-compile \
         --target-os=$host_os --arch=$host_cpu --cross-prefix=$host_alias-"
   fi
 
@@ -317,10 +320,10 @@ else
     # http://trac.macosforge.org/projects/macports/ticket/13725 for more
     # info.
     darwin*) 
-      ac_configure_args="$ac_configure_args --disable-mmx --disable-altivec"
+      embffmpeg_configure_args="$embffmpeg_configure_args --disable-mmx --disable-altivec"
       ;;
     mingw32*)
-      ac_configure_args="$ac_configure_args --enable-memalign-hack"
+      embffmpeg_configure_args="$embffmpeg_configure_args --enable-memalign-hack"
       WIN32_LIBS="-lws2_32"
       ;;
     *)
@@ -328,16 +331,46 @@ else
       ;;
   esac
 
-  # append extra configure options to ac_configure_args if needed
+  dnl checks for extra enable/disable flags
+  FFMPEG_OPTS="`$srcdir/gst-libs/ext/ffmpeg/configure --help`"
+  # Let's check if we can disable the building of the ffmpeg binary
+  can_disable=`echo "$FFMPEG_OPTS" | grep 'disable-ffmpeg' | wc -l`
+  if test "$can_disable" != "0"; then
+    embffmpeg_configure_args="$embffmpeg_configure_args --disable-ffmpeg"
+  fi
+  dnl check if libswscale needs enabling explicitly
+  can_enable=`echo "$FFMPEG_OPTS" | grep 'enable-swscale' | wc -l`
+  if test "$can_enable" != "0"; then
+    embffmpeg_configure_args="$embffmpeg_configure_args --enable-swscale"
+  fi
+
+  # append extra configure options to embffmpeg_configure_args if needed
   if test "x$with_ffmpeg_extra_configure" != "xno"; then
-    ac_configure_args="$ac_configure_args $with_ffmpeg_extra_configure"
+    embffmpeg_configure_args="$embffmpeg_configure_args $with_ffmpeg_extra_configure"
   fi
 
   AC_SUBST(FFMPEG_CO_DIR)
   AC_SUBST(FFMPEG_SVN)
   AC_SUBST(FFMPEG_REVISION)
   AC_SUBST(FFMPEG_EXTERNALS_REVISION)
-  AC_CONFIG_SUBDIRS(gst-libs/ext/ffmpeg)
+  AC_CONFIG_COMMANDS([configure-embedded-ffmpeg],
+    [echo "Configuring included FFmpeg instance with args $embffmpeg_configure_args"
+     origdir=`pwd`
+     dnl Don't put path on the configure call when not needed, as FFmpeg's configure relies on it
+     dnl to detect out-of-tree builds
+     if test -z "$srcdir" -o "$srcdir" = .; then
+       confcmd=./configure
+     else
+       confcmd="$origdir"/"$ac_top_srcdir"/gst-libs/ext/ffmpeg/configure
+     fi
+
+     AS_MKDIR_P(["$ac_top_build_prefix"gst-libs/ext/ffmpeg])
+     cd "$ac_top_build_prefix"gst-libs/ext/ffmpeg &&
+         $confcmd $embffmpeg_configure_args ||
+         AC_MSG_ERROR([Failed to configure embedded FFmpeg tree])
+     cd "$origdir"
+    ],
+    [embffmpeg_configure_args="$embffmpeg_configure_args"])
   AC_MSG_NOTICE([Using included FFMpeg code])
 fi