sudo apt-get install mkvtoolnix

mkvmerge -o out.mkv title1.mkv +title2.mkv +title4.mkv +title5.mkv +title7.mkv +title8.mkv +title9.mkv +title10.mkv

• It seems like it is important to add “+” to every input file after the first file

avconv -i input.mkv -codec copy output.mp4