first mic delay tests.

in the main menu: enter the sing menu and go back (i don't know why this
is necessary)
press W to play the wave file and measure the latency (shown on the top
right). try this multiple times to figure out what the actual latency
is.
press M to play the same tone via MIDI output and measure the latency.
on my system MIDI is 150ms slower than playing the wave file

src/base/UMusic.pas

@@ -609,6 +609,7 @@   TSoundLibrary = class
       Change:  TAudioPlaybackStream;
       Option:  TAudioPlaybackStream;
       Click:   TAudioPlaybackStream;
+      Ping:   TAudioPlaybackStream;
       Applause:TAudioPlaybackStream;
       BGMusic: TAudioPlaybackStream;
 
@@ -990,6 +991,7 @@ procedure TSoundLibrary.LoadSounds();
   Change  := AudioPlayback.OpenSound(SoundPath.Append('select music change music 50.mp3'));
   Option  := AudioPlayback.OpenSound(SoundPath.Append('option change col.mp3'));
   Click   := AudioPlayback.OpenSound(SoundPath.Append('rimshot022b.wav'));
+  Ping    := AudioPlayback.OpenSound(SoundPath.Append('ping.wav'));
   Applause:= AudioPlayback.OpenSound(SoundPath.Append('Applause.mp3'));
 
   BGMusic := AudioPlayback.OpenSound(SoundPath.Append('background track.mp3'));
@@ -1006,6 +1008,7 @@ procedure TSoundLibrary.UnloadSounds();
   FreeAndNil(Change);
   FreeAndNil(Option);
   FreeAndNil(Click);
+  FreeAndNil(Ping);
   FreeAndNil(Applause);
   FreeAndNil(BGMusic);
 end;

src/menu/UDisplay.pas

@@ -113,6 +113,8 @@   TDisplay = class
 
       procedure SaveScreenShot;
 
+      procedure DrawDelay(Delay: Integer);
+
       function  Draw: boolean;
 
       // TODO rewrite ParseInput to include handling/suppressing input as return, use KeepGoing as by-reference
@@ -889,6 +891,19 @@ function TDisplay.ConsoleParseMouse(MouseButton: integer; BtnDown: boolean; X, Y
   end;
 end;
 
+procedure TDisplay.DrawDelay(Delay: Integer);
+begin
+  // set font specs using UDisplay methods
+  SetFontFamily(0);
+  SetFontStyle(ftRegular);
+  SetFontSize(21);
+  SetFontItalic(false);
+  glColor4f(0, 0, 0, 1);
+  SetFontPos(605, 0);
+  glPrint('Delay measured: ' + IntToStr(Delay) + ' ms');
+  glColor4f(1, 1, 1, 1);
+end;
+
 //------------
 // DrawDebugInformation - procedure draw fps and some other informations on screen
 //------------

src/screens/UScreenMain.pas

@@ -39,9 +39,13 @@ interface
   UFiles,
   UMenu,
   UMusic,
+  URecord,
   UScreenSong,
   USong,
   UThemes,
+  MidiOut,
+  MidiCons,
+  Math,
   MD5,
   sdl2,
   SysUtils;
@@ -52,6 +56,10 @@   TScreenMain = class(TMenu)
   public
     TextDescription:     integer;
     TextDescriptionLong: integer;
+    PingTime:            integer;
+    PingResponse:        integer;
+    CurrentSound:        TCaptureBuffer;
+    MidiOut:             TMidiOutput;
 
     constructor Create; override;
     function ParseInput(PressedKey: Cardinal; CharCode: UCS4Char;
@@ -111,6 +119,24 @@ function TScreenMain.ParseInput(PressedKey: Cardinal; CharCode: UCS4Char;
         end;
       end;
 
+      SDLK_W: begin
+        SoundLib.Ping.Volume := 1.0;
+        PingResponse := 0;
+        PingTime := SDL_GetTicks;
+        SoundLib.Ping.Play;
+        Exit;
+      end;
+
+      SDLK_M: begin
+        SoundLib.Ping.Volume := 1.0;
+        PingResponse := 0;
+        PingTime := SDL_GetTicks;
+        MidiOut.PutShort($B1, $7, 127);
+        MidiOut.PutShort($81, 24 + 60, 127);
+        MidiOut.PutShort($91, 24 + 60, 127);
+        Exit;
+      end;
+
       SDLK_J: begin
         FadeTo(@ScreenJukeboxPlaylist, SoundLib.Start);
         Exit;
@@ -304,6 +330,12 @@ constructor TScreenMain.Create;
   Interaction := 0;
 
   WantSoftwareRenderingMsg := SoftwareRendering;
+
+  PingTime := 0;
+  PingResponse := 0;
+
+  MidiOut := TMidiOutput.Create(nil);
+  MidiOut.Open;
 end;
 
 procedure TScreenMain.OnShow;
@@ -322,6 +354,8 @@ procedure TScreenMain.OnShow;
   * at the moment there is no better place for this
   *}
   Party.Clear;
+
+  AudioInput.CaptureStart;
 end;
 
 function TScreenMain.Draw: boolean;
@@ -336,6 +370,18 @@ function TScreenMain.Draw: boolean;
       ScreenPopupError.ShowPopup(Language.Translate('ERROR_SOFTWARE_RENDERING'));
     end;
   end;
+
+  CurrentSound := AudioInputProcessor.Sound[0];
+  CurrentSound.AnalyzeBuffer;
+
+  if (CurrentSound.ToneAbs = 48) and (PingResponse = 0) then
+  begin
+    PingResponse := SDL_GetTicks - PingTime;
+    MidiOut.PutShort($B1, $7, 127);
+    MidiOut.PutShort($81, 24 + 60, 127);
+    MidiOut.PutShort(MIDI_STOP, 0, 0);
+  end;
+  Display.DrawDelay(PingResponse);
 end;
 
 procedure TScreenMain.SetInteraction(Num: integer);