mlt: opencv explicitly, add deps SDL2, libexif to enable more

* needs 'which' to find bins from ladspa-sdk, add
* cleanup a bit, qt seems fine as-is (?)

pkgs/development/libraries/mlt/default.nix

@@ -1,7 +1,7 @@
-{ stdenv, fetchFromGitHub, makeWrapper, pkgconfig
-, SDL, ffmpeg, frei0r, libjack2, libdv, libsamplerate
+{ stdenv, fetchFromGitHub, makeWrapper, pkgconfig, which
+, SDL, SDL2, ffmpeg, frei0r, libjack2, libdv, libsamplerate
 , libvorbis, libxml2, movit, sox, qtbase, qtsvg, gtk2
-, fftw, vid-stab, opencv3, ladspa-sdk
+, fftw, vid-stab, opencv3, ladspa-sdk, libexif
 }:
 
 let inherit (stdenv.lib) getDev; in
@@ -17,43 +17,25 @@ stdenv.mkDerivation rec {
     sha256 = "0pzm3mjbbdl2rkbswgyfkx552xlxh2qrwzsi2a4dicfr92rfgq6w";
   };
 
-  nativeBuildInputs = [ makeWrapper pkgconfig ];
+  nativeBuildInputs = [ makeWrapper pkgconfig which ];
   buildInputs = [
-    SDL ffmpeg frei0r libjack2 libdv libsamplerate libvorbis libxml2
+    SDL SDL2 ffmpeg frei0r libjack2 libdv libsamplerate libvorbis libxml2
     movit qtbase qtsvg sox fftw vid-stab opencv3
-    ladspa-sdk gtk2
+    ladspa-sdk libexif gtk2
   ];
 
-  # Mostly taken from documentation previously hosted at:
-  # http://www.kdenlive.org/user-manual/downloading-and-installing-kdenlive/installing-source/installing-mlt-rendering-engine
-  # Which may now be the installation docs here: https://www.mltframework.org/docs/install
   configureFlags = [
     "--enable-gpl"
     "--enable-gpl3"
-    #"--avformat-swscale"
     "--enable-opengl"
+    # must be enabled explicitly
+    "--enable-opencv" 
   ];
 
-  # mlt is unable to cope with our multi-prefix Qt build
-  # because it does not use CMake or qmake.
-  NIX_CFLAGS_COMPILE = [ "-I${getDev qtsvg}/include/QtSvg" ];
-
-  CXXFLAGS = "-std=c++11";
-
   enableParallelBuilding = true;
 
   postInstall = ''
     wrapProgram $out/bin/melt --prefix FREI0R_PATH : ${frei0r}/lib/frei0r-1
-
-    # Remove an unnecessary reference to movit.dev.
-    s=${movit.dev}/include
-    t=$(for ((i = 0; i < ''${#s}; i++)); do echo -n X; done)
-    sed -i $out/lib/mlt/libmltopengl.so -e "s|$s|$t|g"
-
-    # Remove an unnecessary reference to movit.dev.
-    s=${qtbase.dev}/include
-    t=$(for ((i = 0; i < ''${#s}; i++)); do echo -n X; done)
-    sed -i $out/lib/mlt/libmltqt.so -e "s|$s|$t|g"
   '';
 
   passthru = {