normalize video track timescale (#123)

ErsatzTV.Core/FFmpeg/FFmpegPlaybackSettings.cs

@@ -27,5 +27,6 @@ namespace ErsatzTV.Core.FFmpeg
         public string AudioCodec { get; set; }
         public bool Deinterlace { get; set; }
         public Option<string> FrameRate { get; set; }
+        public Option<int> VideoTrackTimeScale { get; set; }
     }
 }

ErsatzTV.Core/FFmpeg/FFmpegPlaybackSettingsCalculator.cs

@@ -91,6 +91,8 @@ namespace ErsatzTV.Core.FFmpeg
                         result.FrameRate = string.IsNullOrWhiteSpace(ffmpegProfile.FrameRate)
                             ? None
                             : Some(ffmpegProfile.FrameRate);
+
+                        result.VideoTrackTimeScale = 90000;
                     }
 
                     if (result.ScaledSize.IsSome || result.PadToDesiredResolution ||

ErsatzTV.Core/FFmpeg/FFmpegProcessBuilder.cs

@@ -330,6 +330,16 @@ namespace ErsatzTV.Core.FFmpeg
             return this;
         }
 
+        public FFmpegProcessBuilder WithVideoTrackTimeScale(Option<int> videoTrackTimeScale)
+        {
+            videoTrackTimeScale.IfSome(timeScale =>
+            {
+                _arguments.Add("-video_track_timescale");
+                _arguments.Add($"{timeScale}");
+            });
+            return this;
+        }
+
         public FFmpegProcessBuilder WithDeinterlace(bool deinterlace)
         {
             _complexFilterBuilder = _complexFilterBuilder.WithDeinterlace(deinterlace);

ErsatzTV.Core/FFmpeg/FFmpegProcessService.cs

@@ -49,7 +49,8 @@ namespace ErsatzTV.Core.FFmpeg
                 .WithRealtimeOutput(playbackSettings.RealtimeOutput)
                 .WithSeek(playbackSettings.StreamSeek)
                 .WithInputCodec(path, playbackSettings.HardwareAcceleration, videoStream.Codec)
-                .WithFrameRate(playbackSettings.FrameRate);
+                .WithFrameRate(playbackSettings.FrameRate)
+                .WithVideoTrackTimeScale(playbackSettings.VideoTrackTimeScale);
 
             playbackSettings.ScaledSize.Match(
                 scaledSize =>