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. And I highly recommend you use WonderFox DVD Ripper Pro. It's a professional and reliable DVD ripper, allowing you to copy DVD to VIDEO_TS , rip DVD to ISO, and convert DVD to digital formats like MP4, AVI, MOV, MPG, H264, etc. You can also use it to add subtitles to DVD. Now free download this excellent DVD ripper and convert DVD to VIDEO_TS with the simple steps below.