Trimming video with avconv

To remove a section from the start of a video

Use the ss  (start seek) option before the i  (input filename) parameter. The following would trim the first 35 seconds from the start of the video.:

Using the codec copy  option means it won’t alter the audio/video streams, and means the operation happens is nearly instantly

To trim the end off a video

Use the t option to specify the number of seconds you want to trim up to from the start of the video. The following would keep just the first 2 minutes of the video:

 To keep just a section from the middle of a video

The two options above can be used in conjuntion, i.e. the following would keep 2 minutes of footage, starting at 35 seconds into the original video: