obs-studio: package the missing ndi library to make the obs-ndi plug-in actually work

pkgs/applications/video/obs-studio/hardcode-ndi-path.patch

···
+diff --git a/src/obs-ndi.cpp b/src/obs-ndi.cpp
+index 493831c..7b0f8db 100644
+--- a/src/obs-ndi.cpp
++++ b/src/obs-ndi.cpp
+@@ -197,11 +197,7 @@ const char* obs_module_description()
+ const NDIlib_v4* load_ndilib()
+ {
+ 	QStringList locations;
+-	locations << QString(qgetenv(NDILIB_REDIST_FOLDER));
+-#if defined(__linux__) || defined(__APPLE__)
+-	locations << "/usr/lib";
+-	locations << "/usr/local/lib";
+-#endif
++	locations << "@NDI@/lib";
+ 
+ 	for (QString path : locations) {
+ 		blog(LOG_INFO, "Trying '%s'", path.toUtf8().constData());

pkgs/applications/video/obs-studio/obs-ndi.nix

···
 # somewhat manually install this:
 
 # nix-env -f "<nixpkgs>" -iA obs-ndi
-# mkdir -p ~/.config/obs-studio/plugins
-# ln -s ~/.nix-profile/share/obs/obs-plugins/obs-ndi ~/.config/obs-studio/plugins/
+# mkdir -p ~/.config/obs-studio/plugins/bin
+# ln -s ~/.nix-profile/lib/obs-plugins/obs-ndi.so ~/.config/obs-studio/plugins/bin/
 
-{ stdenv, fetchFromGitHub, obs-studio, cmake, qt5 }:
+{ stdenv, fetchFromGitHub, obs-studio, cmake, qt5, ndi }:
 
 stdenv.mkDerivation rec {
   pname = "obs-ndi";
   version = "4.7.1";
+
+  nativeBuildInputs = [ cmake ];
+  buildInputs = [ obs-studio qt5.qtbase ndi ];
 
   src = fetchFromGitHub {
     owner = "Palakis";
···
     sha256 = "040fkbf3f3qgqcrd3072y3zrjb4fwga8zr10jym744xd7bgyylqh";
   };
 
-  patches = [ ./fix-search-path.patch ];
+  patches = [ ./fix-search-path.patch ./hardcode-ndi-path.patch ];
 
-  nativeBuildInputs = [ cmake ];
-  buildInputs = [ obs-studio qt5.qtbase ];
+  postPatch = "sed -i -e s,@NDI@,${ndi},g src/obs-ndi.cpp";
 
   cmakeFlags = [
     "-DLIBOBS_INCLUDE_DIR=${obs-studio}/include/obs"

pkgs/development/libraries/ndi/default.nix

···
+{ stdenv, requireFile, avahi }:
+
+stdenv.mkDerivation rec {
+  pname = "ndi";
+  version = "4";
+
+  src = requireFile rec {
+    name    = "InstallNDISDK_v${version}_Linux.tar.gz";
+    sha256  = "1hac5npyg8nifs9ipj34pkn0zjyx8774x3i3h8znhmijx2j2982p";
+    message = ''
+      In order to use the NDI SDK, you need to comply with NewTek's license and
+      download the Linux version ${version} tarball from:
+
+      ${meta.homepage}
+
+      Once you have downloaded the file, please use the following command and
+      re-run the installation:
+
+      nix-prefetch-url file://\$PWD/${name}
+    '';
+  };
+
+  buildInputs = [ avahi ];
+
+  unpackPhase = ''
+    unpackFile ${src}
+    echo y | ./InstallNDISDK_v4_Linux.sh
+    sourceRoot="NDI SDK for Linux";
+  '';
+
+  installPhase = ''
+    mkdir $out
+    mv bin/x86_64-linux-gnu $out/bin
+    for i in $out/bin/*; do
+      patchelf --set-interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" "$i"
+    done
+    patchelf --set-rpath "${avahi}/lib:${stdenv.cc.libc}/lib" $out/bin/ndi-record
+    mv lib/x86_64-linux-gnu $out/lib
+    for i in $out/lib/*; do
+      if [ -L "$i" ]; then continue; fi
+      patchelf --set-rpath "${avahi}/lib:${stdenv.cc.libc}/lib" "$i"
+    done
+    mv include examples $out/
+    mkdir -p $out/share/doc/${pname}-${version}
+    mv licenses $out/share/doc/${pname}-${version}/licenses
+    mv logos $out/share/doc/${pname}-${version}/logos
+    mv documentation/* $out/share/doc/${pname}-${version}/
+  '';
+
+  # Stripping breaks ndi-record.
+  dontStrip = true;
+
+  meta = with stdenv.lib; {
+    homepage = "https://ndi.tv/sdk/";
+    description = "NDI Software Developer Kit";
+    platforms = ["x86_64-linux"];
+    hydraPlatforms = [];
+    license = licenses.unfree;
+  };
+}

pkgs/top-level/all-packages.nix

···
     then null
     else callPackage ../development/libraries/ncurses { };
 
+  ndi = callPackage ../development/libraries/ndi { };
+
   neardal = callPackage ../development/libraries/neardal { };
 
   neon = callPackage ../development/libraries/neon { };