private async Task prelimProcessing()
{
tags = new Tags(inputFileName);
encodingInfo = new EncodingInfo(inputFileName);
chapters = new Chapters(inputFileName, tags.duration.TotalSeconds);
var defaultFilename = Path.Combine(
Path.GetDirectoryName(inputFileName),
PathLib.ToPathSafeString(tags.author),
PathLib.ToPathSafeString(tags.title) + ".m4b"
);
// set default name
SetOutputFilename(defaultFilename);
await Task.Run(() => saveCover(inputFileName));
}