So, if you're looking for a fully featured video transcoder with an easy to use GUI, then you should consider HandBrake.
*. Supports all sorts of DVDs and Blue-Ray disks (unencrypted ones only).
*. Supports some .VOB extensions, TS and M2TS files.
*. VIDEO_TS folder and DVD image file support.
*. Crop, change bitrate, calculate bit-rate, change file-size, add effects to your videos, change resolutions... it's all there!.
*. Currently supports MP4(M4V) and MKV container formats only.
*. Built in presets such as iPod, iPhone, Apple TV, high or normal quality settings.
*. MPEG-4(ffmpeg), H.264(x264), or Theora(libtheora), AAC, CoreAudio AAC (OS X Only), MP3, or Vorbis. AC-3 codec support.
*. Live video preview.
*. Select/un-select chapters..., etc.
So, if you use Ubuntu and want to install HandBrake, then as usual, open your Terminal and issue the below command.
sudo add-apt-repository ppa:stebbins/handbrake-snapshots
sudo aptitude update
sudo aptitude install handbrake-gtk