Due to limitations of both OCR and the images used for subtitles you'll need to help VobSub out during the OCR process. This basically allows your computer to 'read' the text and output the results. OCR The key to converting from image based subtitles to text based is a process called Optical Character Recognition, or OCR.
Fortunately VobSub also includes a tool capable of converting subtitles to text-based formats like SRT or SSA. But there are still times when you need something different, especially when dealing with older file formats like AVI where subtitles need to be in text format rather than images like VobSub rips from a DVD.
VobSub's IDX and SUB subtitle format has beocme very popular do in large part to its flexibility and nearly universal compatibility with media players.
