diff --git a/FFMpegCore/FFMpeg/Arguments/SetMirrorVideo.cs b/FFMpegCore/FFMpeg/Arguments/SetMirrorVideo.cs
new file mode 100644
index 0000000..4c18cef
--- /dev/null
+++ b/FFMpegCore/FFMpeg/Arguments/SetMirrorVideo.cs
@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace FFMpegCore.Arguments
+{
+    public class SetMirrorVideo : IArgument
+    {
+        public string Text { get; set; } = "-vf \"hflip\"";
+    }
+}
diff --git a/FFMpegCore/FFMpeg/FFMpegArguments.cs b/FFMpegCore/FFMpeg/FFMpegArguments.cs
index 847e68c..5aa913d 100644
--- a/FFMpegCore/FFMpeg/FFMpegArguments.cs
+++ b/FFMpegCore/FFMpeg/FFMpegArguments.cs
@@ -57,6 +57,12 @@ private FFMpegArgumentProcessor ToProcessor(IOutputArgument argument, Action<FFM
         {
             var args = new FFMpegArgumentOptions();
             addArguments?.Invoke(args);
+
+            if (argument is OutputPipeArgument && !Arguments.Any(x => x is ForceFormatArgument))
+            {
+                args.ForceFormat("matroska");
+            }
+
             Arguments.AddRange(args.Arguments);
             Arguments.Add(argument);
             return new FFMpegArgumentProcessor(this);