finding great similar answer here
If you chop random bytes out the movie is likely not playable. The player might crash or fail to resynchronize the stream – the video might just stop. Plus, you're gonna have a hard time figuring out where the "adult" bytes are, so to speak.
If you already know where the parts are that you want to cut out, I would edit the file in any of the numerous video editors. Even Windows Movie Maker or iMovie would do the job, and those are easily available on both major OSes.
This is a requested feature for VLC. Not really anything user-friendly out there. Still, VLC offers the possibility to create playlists in a certain format that would mute or skip parts of a file. This is called XSPF. You might be able to figure out the proper format for this.
Also, there's movie-content-editor:
A VLC based editor built in python that allows users to create and use custom filter files to make movies more family friendly. Allows users to have the player automatically mute specific words or skip certain scenes based on the content of those scenes.
And sensible-cinema:
Clean Editing Movie Player allows you watch edited movies by applying delete lists (EDL's) (i.e. "mute out" or "cut out" scenes) to DVD's/files, with preliminary support for also applying them to arbitrary web/internet based players like netflix instant, hulu/hulu plus etc
See also these threads on The VideoLAN Forums: