VLC subtitle manipulation

[saiprasad]

I would like to contribute to VLC. I want to know how I can manipulate subtitle text that is displayed( removing/ adding some text to it). I am able to compile the VLC in ubuntu as of now. Please tell me which file to edit, which function is responsible to display subtitle. I want to add/remove some string to existing subtitle.

[saiprasad]

I would like to clarify my doubt further:
while playing a video subtitle is displayed based on time span. Now if I manually add suffix to every string of subtitle for ex: "#display_on_space_key_press".
This substring should be displayed as a subtitle only when user press space key(ascii value 32). Any help regarding which file and functions to modify will be helpful