diff --git a/include/nana/audio/player.hpp b/include/nana/audio/player.hpp
index 278e0ecc..24378214 100644
--- a/include/nana/audio/player.hpp
+++ b/include/nana/audio/player.hpp
@@ -4,7 +4,10 @@
 #include <nana/deploy.hpp>
 
 namespace nana{	namespace audio
-{       /// play an audio file in Windows WAV format
+{       /// class player
+        /// \brief play an audio file in PCM Windows WAV format 
+        ///
+        /// \include  audio_player.cpp
 	class player
 		: private nana::noncopyable
 	{
diff --git a/include/nana/gui/screen.hpp b/include/nana/gui/screen.hpp
index ef9126e8..06c344ee 100644
--- a/include/nana/gui/screen.hpp
+++ b/include/nana/gui/screen.hpp
@@ -34,27 +34,38 @@ namespace nana
 		virtual const ::nana::rectangle& workarea() const = 0;
 	};
 
+    /// Provides some functions to get the metrics of the monitors \include screen.cpp
 	class screen
 	{
 		struct implement;
 	public:
-		static ::nana::size desktop_size();
-		static ::nana::size primary_monitor_size();
+        /// gets the size in pixel of the whole virtual desktop
+		static ::nana::size desktop_size();        
+
+        /// gets the resolution in pixel of the primary monitor, 
+        /// if there is only one monitor installed in the system, 
+        /// the return value of primary_monitor_size is equal to desktop_size's.
+		static ::nana::size primary_monitor_size();  
+
 
 		screen();
 
 		/// Reload has no preconditions, it's safe to call on moved-from
 		void reload();
 
-		/// Returns the number of display monitors
+		/// Returns the number of display monitors installed in the system
 		std::size_t count() const;
 
+        /// gets the display monitor that contains the specified point
 		display& from_point(const point&);
+
+        /// gets the display monitor that contains the specified window
 		display& from_window(window);
 
 		display& get_display(std::size_t index) const;
 		display& get_primary() const;
 
+        /// applies a given function to all display monitors
 		void for_each(std::function<void(display&)>) const;
 	private:
 		std::shared_ptr<implement> impl_;
diff --git a/source/audio/detail/audio_stream.cpp b/source/audio/detail/audio_stream.cpp
index 96def3d9..998b85bf 100644
--- a/source/audio/detail/audio_stream.cpp
+++ b/source/audio/detail/audio_stream.cpp
@@ -8,7 +8,8 @@ namespace nana{	namespace audio
 		//class audio_stream
 			bool audio_stream::open(const nana::string& file)
 			{
-				fs_.open(static_cast<std::string>(nana::charset(file)), std::ios::binary);
+				std::string fname{nana::charset(file)};//static_cast<std::string>()
+                fs_.open(fname, std::ios::binary);
 				if(fs_)
 				{
 					wave_spec::master_riff_chunk riff;