Add standalone NVENC encoder

src/nvenc/nvenc_d3d11.h

@@ -0,0 +1,35 @@
+#pragma once
+#ifdef _WIN32
+
+  #include <comdef.h>
+  #include <d3d11.h>
+
+  #include "nvenc_base.h"
+
+namespace nvenc {
+
+  _COM_SMARTPTR_TYPEDEF(ID3D11Device, IID_ID3D11Device);
+  _COM_SMARTPTR_TYPEDEF(ID3D11Texture2D, IID_ID3D11Texture2D);
+
+  class nvenc_d3d11 final: public nvenc_base {
+  public:
+    nvenc_d3d11(ID3D11Device *d3d_device);
+    ~nvenc_d3d11();
+
+    ID3D11Texture2D *
+    get_input_texture();
+
+  private:
+    bool
+    init_library() override;
+
+    bool
+    create_and_register_input_buffer() override;
+
+    HMODULE dll = NULL;
+    const ID3D11DevicePtr d3d_device;
+    ID3D11Texture2DPtr d3d_input_texture;
+  };
+
+}  // namespace nvenc
+#endif