Dave use handbrake, its easy and quality is excellent and its fast.
U can set video size encode>2pass>1st pass turbo + Audio whatever u want and there u go.
<But why on the earth would u want to go to .avi?? Huge step back as avi is not as sharp,does not have rich color,size is bigger vs MKV and much more >
Its like going from Corvette to Toyota Camry...
http
/www.filehippo.com/download_handbrake/tech/