public static void Convert(GrabbedMedia videoStream, GrabbedMedia audioStream, string videoPath, string audioPath, string outputPath)
{
var builder = new MediaBuilder(outputPath);
builder.AddStreamSource(videoPath, MediaStreamType.Video);
builder.AddStreamSource(audioPath, MediaStreamType.Audio);
builder.OutputMimeType = videoStream.Format.Mime;
builder.OutputShortName = videoStream.Format.Extension;
builder.Build();
}