Yes, it would. -vf are video filters, ie. they affect the output video stream. EDIT: Misread your question, but yeah, I think you can make -vf ass read the ASS

Yes, it would. -vf are video filters, ie. they affect the output video stream. EDIT: Misread your question, but yeah, I think you can make -vf ass read the ASS file from the (MKV, I assume?) file itself.