Other way you may change subtites files encoding to UTF-8
I've experienced this before, and I found it's because of subtitles' font, use Subtitle Editor to edit your subtitle's font!
You can get Subtitle Editor two ways, Download from it's house http://home.gna.org/subtitleeditor/ or via PPA.
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install subtitleeditor
- Right click on subtitle → open with → Subtitle Editor
- Then Tools → Style Editor, and there you can change your subtitle's font.