--- ffmpeg-4.1/configure.orig	2018-11-05 23:22:33.000000000 +0000
+++ ffmpeg-4.1/configure	2019-01-17 19:13:20.212000000 +0000
@@ -5268,6 +5268,12 @@
         ranlib=:
         enable dos_paths
         ;;
+    midipix*)
+        target_os=midipx
+        disable symver
+        enabled x86_64 && objformat="win64" || objformat="win32"
+	enable shared
+        ;;
     cygwin*)
         target_os=cygwin
         shlibdir_default="$bindir_default"
@@ -5764,7 +5770,6 @@
         disabled x86asm && die "nasm/yasm not found or too old. Use --disable-x86asm for a crippled build."
         X86ASMFLAGS="-f $objformat"
         enabled pic               && append X86ASMFLAGS "-DPIC"
-        test -n "$extern_prefix"  && append X86ASMFLAGS "-DPREFIX"
         case "$objformat" in
             elf*) enabled debug && append X86ASMFLAGS $x86asm_debug ;;
         esac