I needed to join several video files into one larger. All files were of the same codec, container (AVI) so it should have been simple. But instead I needed to try several programs to actually succeed. Those that I tried didn’t work as expected or made unbelievable results (one made file 315 GB large from 7 files large 1,3 GB in total — that didn’t work).
The only program that worked is AVI Joiner. Unfortunately, it is a shareware program but it has a trial period (which was enough for me this time).
Files are merged relatively quickly and results are great: it’s doing joining fast, quality is identical as from original files, and size is same as sum of all files.
AVI Joiner is very simple to use so I recommend it to everyone that needs quick joining of AVI files.