-map filtering

Add map filtering to choose videostream

FFMpegCore/FFMpeg/Arguments/MapStreamArgument.cs

@@ -0,0 +1,17 @@
+namespace FFMpegCore.Arguments
+{
+    /// <summary>
+    /// Represents choice of video stream, works with one input file
+    /// </summary>
+    public class MapStreamArgument : IArgument
+    {
+        public readonly int VideoStream;
+
+        public MapStreamArgument(int videoStreamNum)
+        {
+            VideoStream = videoStreamNum;
+        }
+
+        public string Text => $"-map 0:{VideoStream}";
+    }
+}

FFMpegCore/FFMpeg/FFMpegArguments.cs

@@ -59,7 +59,8 @@ private FFMpegArguments(IInputArgument inputArgument)
         public FFMpegArguments WithDuration(TimeSpan? duration) => WithArgument(new DurationArgument(duration));
         public FFMpegArguments WithFastStart() => WithArgument(new FaststartArgument());
         public FFMpegArguments WithFrameOutputCount(int frames) => WithArgument(new FrameOutputCountArgument(frames));
-        
+        public FFMpegArguments WithVideoStream(int videoStreamNumber) => WithArgument(new MapStreamArgument(videoStreamNumber));
+
         public FFMpegArguments UsingShortest(bool shortest = true) => WithArgument(new ShortestArgument(shortest));
         public FFMpegArguments UsingMultithreading(bool multithread) => WithArgument(new ThreadsArgument(multithread));
         public FFMpegArguments UsingThreads(int threads) => WithArgument(new ThreadsArgument(threads));