add support for input audio/video sync

MediaBrowser.Api/Playback/BaseStreamingService.cs

@@ -1503,6 +1503,16 @@ namespace MediaBrowser.Api.Playback
                 inputModifier += " -acodec " + state.InputAudioCodec;
             }
 
+            if (!string.IsNullOrEmpty(state.InputAudioSync))
+            {
+                inputModifier += " -async " + state.InputAudioSync;
+            }
+
+            if (!string.IsNullOrEmpty(state.InputVideoSync))
+            {
+                inputModifier += " -vsync " + state.InputVideoSync;
+            }
+
             if (state.ReadInputAtNativeFramerate)
             {
                 inputModifier += " -re";

MediaBrowser.Api/Playback/StreamState.cs

@@ -64,6 +64,9 @@ namespace MediaBrowser.Api.Playback
         public string AudioSync = "1";
         public string VideoSync = "vfr";
 
+        public string InputAudioSync { get; set; }
+        public string InputVideoSync { get; set; }
+ 
         public bool DeInterlace { get; set; }
 
         public bool ReadInputAtNativeFramerate { get; set; }