Mencoder - Movie Encoder for Linux

Mencoder is a simple movie encoder, designed to encode MPlayer-playable movies (AVI/ASF/OGG/DVD/VCD/VOB/MPG/MOV/VIV/FLI/RM/NUV/NET) to other MPlayer-playable formats. It can encode with various codecs, like DivX4 (1 or 2 passes), libavcodec, PCM/MP3/VBRMP3 audio. It also has stream copying and video resizing abilities.

Since it uses the same code as MPlayer, it also features the same huge number of highly-configurable video and audio filters to transform the video and audio stream.

In order to convert the videos all you have to do is open a console and issued the proper commands. For easy tasks this is the better way, because it's faster and you can just copy/paste the bash lines through different console sessions and have Mencoder multitask all of your videos to be converted. 

If you have some more complicated tasks to do (extracting subtitles, cropping video frame, deinterlace, change endpoints) i suggest that you do it with a visual tool, like Avidemux.

Among the file types mencoder can handle are MPEG/VOB, AVI, ASF/WMA/WMV, RM, QT/MOV/MP4, Ogg/OGM, MKV, VIVO, FLI, and FLV, basically, the command structure is:

[mencoder] + [input file name] + [audio options] + [video options] + [output file name]

Here's a simple command that converts an MPG file to AVI format:

mencoder file.mpg -o file.avi -ovc lavc -oac lavc

Suppose you have a folder full of small video files of different types and would like to merge them into one big movie for easy watching. First, rename them so that they're in the order you want them to appear in the final video, then use:

mencoder * -o output.avi

To convert a video file to run on a device running iPodLinux, use:

mencoder -ovc raw -ofps 15 -oac pcm -vf scale=176:-2,expand=176:132,format=bgr16 input.file -o output.avi

Convert 3gp movies to avi:

mencoder mymovie.3gp -ovc lavc -lavcopts vcodec=msmpeg4v2 -oac mp3lame -lameopts vbr=3 -o mymovie.avi''