I have a 40PFL5507H/12. when I watch movie over USB, the subtitle was not read on the screen.

I searched and find philips FQA Answer:

Your TV supports the use of external subtitles with file name extension srt, sub and sami exclusively when you watch movies from a USB memory device. Only Latin-1 and Western European (ISO-8859-1) subtitle character sets are supported.

But no matter how I try, still can not read english subtitles on the screen.
I can read subtitles when I watch the same movie on my computer.