Add a configure-time check using avcodec_find_encoder_by_name("libmp3lame") to

look for LAME support.  Unfortunatly FFMPEG's internal MP3 support is rather
broken.  If --enable-broken-mp3 is supplied configure will continue otherwise
LAME must be compiled into FFMPEG.

Originally committed to SVN as r1989.

configure.in

@@ -225,6 +225,49 @@ if test "$with_ffmpeg" != "no"; then
   fi
 fi
 
+
+if test "$with_ffmpeg" = "yes"; then
+
+AC_ARG_ENABLE(broken-mp3, [--enable-broken-mp3   Enable the use of FFMPEG w/out LAME compiled in.])
+  AC_MSG_CHECKING([whether ffmpeg has LAME compiled in])
+  aegisub_save_LDFLAGS="$LDFLAGS"
+  AC_LANG(C)
+  LDFLAGS="$LDFLAGS $AVCODEC_LDFLAGS"
+  AC_RUN_IFELSE(
+    [AC_LANG_PROGRAM([#include <ffmpeg/avcodec.h>],
+    [
+      avcodec_register_all();
+      if (avcodec_find_encoder_by_name("libmp3lame"))
+        return 1;
+    ])
+  ],
+  ffmpeg_mp3_broken="yes",
+  ffmpeg_mp3_broken="no")
+
+  LDFLAGS="$aegisub_save_LDFLAGS"
+  AC_LANG(C++)
+fi
+
+if test $ffmpeg_mp3_broken = "yes"; then
+  AC_MSG_RESULT([no])
+  AC_MSG_NOTICE([
+***********************************************************************
+* Your installation of FFMPEG does not have LAME support compiled in.
+* This will result in _broken_ mp3 decoding, either recompile FFMPEG
+* with LAME support, or supply --with-broken-mp3 (With this you will have
+* to demux the audio, convert to wav and load the audio/wav seperately.)
+*   * LAME can be found at: http://lame.sourceforge.net/index.php
+***********************************************************************
+  ])
+echo "enable_broken_mp3: $enable_broken_mp3"
+  if test "$enable_broken_mp3" != "yes"; then
+    AC_MSG_FAILURE([Please read.])
+  fi
+else
+  AC_MSG_RESULT([yes])
+fi
+
+
 AC_SUBST(SWSCALE_LDFLAGS)
 AC_SUBST(AVCODEC_LDFLAGS)
 AC_SUBST(AVFORMAT_LDFLAGS)