You can use the 'OnProgress' event - ffmpeg Documentation[^] To add a progress tracker using a percentage, add the following to your code - textBox_taskMsg.Text = "Task is being performed.. This may take some time."; string[] files = { textBox_Source1.Text, textBox_Source2.Text }; string output = textBox_Source1.Text + "_merged.mp4"; var conversion = await FFmpeg.Conversions.FromSnippet.Concatenate(output, files) .OnProgress += (sender, args) => { //Calculate and display the progress as a percentage to your uswer... double progressPercentage = args.Percent; textBox_taskMsg.Text = $"Merging... {progressPercentage:F2}% complete"; }; await conversion.Start(); textBox_taskMsg.Text = "Merge Complete.";

Check the bitrate on the result file from wondershare (windows explorer will show you that) and use VLC to check the codecs the result file contains - H265 for example is a lot more compact than H264 for example, but not everything can read it. But as Dave said, that one would appear to be abandoned - and that may be because it was never finished, or had bugs, or ... you never know. You know you can splice files directly using FFMPEG as an external process? Concatenate – FFmpeg[^] "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!