mkvtoolnix-gui

Notes:

• there is no re-encoding involved, so the merging process takes only a
  couple of seconds
• it can merge other video formats, like avi, mp4, but the output is always mkv
• it can't merge videos with different apect ratios

For more info see the documentation here

Quick how-to:

Click "add", select the first video, then click "append", then select the other videos to append. You can select multiple videos as long as you select them in order or you can append one by one. Then click "Start muxing". You might want to change the output filename. The other options are not really necessary for basic merging. Nevertheless, you can also add multiples subtitles in various formats or languages and also multiple audio tracks.

AVI files - avimerge

Description

avimerge is a versatile tool. It can contatenate several AVI files into one. It can also be used to fix an index of a broken file and can also replace audio tracks or muxes new ones. It can read raw AC3 and MP3 files for multplex- ing.

Installation

sudo apt-get install transcode transcode-utils

Usage

You can merge avi files with:

avimerge -i input1.avi input2.avi -o output.avi

It's encoding-free, so joining the parts usually doesn't take much longer than a minute.

Options

Other available options are:

Usage: avimerge [options]
     -o file                   output file name
     -i file1 [file2 [...]]    input file(s)
     -p file                   multiplex additional audio track from file
     -a num                    select audio track number from input file [0]
     -A num                    select audio track number in output file [next]
     -b n                      handle vbr audio [autodetect]
     -c                        drop video frames in case audio is missing [off]
     -f FILE                   read AVI comments from FILE [off]
     -x FILE                   read AVI index from FILE [off] (see aviindex(1))