Start/end time points for video segments

I have a video, I want to use it in a video segment, but I don't want the entire video, only a portion of it, from t=3s to t=63s. I want an option in the video segment to only take this part of the video in the final output video. Probably using the '-ss' and '-t' options in avconv/ffmpeg. Should default to t=0 and t=TotalDuration..