Well, there's a good reason why SubRip asks you to type in stuff: this way it can tell if some white part of the image is actually a subtitle, as opposed to just white background (when it mistakes the background for a subtitle, you just press Enter for a "null" character).
So, just type in garbage (well, if you want to type in Chinese, using UniCode you should be able to do so using one of those "helper" applications that lets you type in several Latin letters for a Chinese character), and then open the resulting subtitle in SubtitleWorkshop and edit it to your heart's content.
|