As DVD subtitle rippers can only recognize .vob or .ifo files, first you need to convert DVD to a VIDEO_TS file that contains all DVD information including. vob files, .ifo files and .bup files. Therefore, a good DVD Ripper is a must-have. Here I highly recommend WonderFox DVD Ripper Pro. It's a professional and reliable DVD ripper that allows you to copy DVD to VIDEO_TS , copy DVD to ISO and copy DVD to digital formats like MP4, AVI, MOV, 3GP, FLV, etc. You can also use it to add subtitles to DVD. Follow the steps below to convert DVD to VIDEO_TS.