Video Conversion in .net core MVC.

Hello I have use this code for video convert .mts to .mp4 with NReco.VideoConverter.LicenseKey

string fileNameonly = Path.GetFileNameWithoutExtension(Video.FileName);

string outputFileName = Path.ChangeExtension(Video.FileName, ".mp4");

//#pragma warning disable CS0618 // Type or member is obsolete

// Conversion.ToMp4(Video.FileName, outputFileName).Start();

//#pragma warning restore CS0618 // Type or member is obsolete

string filePath = fileNameonly + ".mp4";

but i have face a problem.Format are not correct Please help me