Merge many video files using splicer.

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C#

ffmpeg

Hello, I am trying to make a program that copies a specific video until the total length is longer than a specified amount. I need help trying to join them.
Here is my joining code.

// videos is a List<string> containing a list of every single copied video's path.
// dir is the current directory returned by Directory.GetCurrentDirectory()
// outputVideoSelect.FileName is a user specified output file
using Splicer; 
using Splicer.Timeline;
using Splicer.Renderer;

            using (ITimeline timeline = new DefaultTimeline())
            {
                IGroup group = timeline.AddVideoGroup(32, 720, 576);
                
                for (int v = 1; v < videos.ToArray().Length; v++) {
                    group.AddTrack().AddVideo(videos[v]);
                }
                

                using (AviFileRenderer renderer = new AviFileRenderer(timeline, $"{dir}\\output.mp4"))
                {
                    renderer.Render();
                }
            }
            File.Move($"{dir}\\output.mp4", $"{outputVideoSelect.FileName}");

What I have tried:

FFMPEG (no luck)
CMD's copy function (no luck)
Using a for loop to make my list of videos to render using Splicer (program throws

An exception of type 'System.Runtime.InteropServices.COMException' occurred in DirectShowLib-2005.dll but was not handled in user code
The filename, directory name, or volume label syntax is incorrect.

)