how to map the grabed iamges(video) to texture?

Do you mean you want to grab a picture of e.g. a business card or a product label and then "read" the text that is written on it, i.e. convert the picture to text?

If yes, be aware that this is a *very* difficult task, especially given that pictures from phone cameras are often of rather poor resolution and the resulting picture might be at a certain angle instead of perfectly perpendicular to the text surface which complicates the matter further. Very challenging!

The magical word here is probably OCR: Optical character recognition. If you search for "ocr algorithms" with Google you will get basic information about this.

I am not aware of open-source or at least freeware OCR implementations ported already to Symbian, but there may be something for another platform that could be ported to Symbian with a reasonable amount of work (say, a few months of work). Starting an OCR implementation from scratch would of course be even harder.