I have movie separated at two parts and when i tried to add subtitles with the Avisub to first and after that to second part it works with no problems. After that i tried other thing : I joined the movies files and subtitles for first part of the movie with this for the second part of the movie and after that i tried to add subtitles with Avisub but it doesn't work. Why? That happens with all movies separated at two or more parts.I can't add subtitles after joining the video files