Here is a quick and simple guide to add subtitle to .mp4 file that you would like to have harcoded subtitles and convert the whole file to iphone4S mp4.
If you would like to create and add permanent subtitle to videos, look at this,how to add subtitle to videos with a software named "GiliSoft Video Converter".
Step 1:
Download and install "GiliSoft Video Converter ".
Step 2:
Load the video files
Also, the videos are available in various video formats: AVI,MPEG,MPEG2 TS,MP4,MKV,WMV,ASF,3GP,3G2, SWF,H.264/ MPEG-4 AVC,H.264/ PSP AVC Video,MOV,FLV etc.Depending on what your subtitle expectations are and which computing platform you use, adding a subtitle track to your video project doesn't need to cost anything.
Download GiliSoft Video Converter (Adding Subtitle to Videos Software ) Windows Version
Buy GiliSoft Video Converter