You can merge a series of .avi files with ffmpeg using the concat filter. However, the concat filter requires that all inputs have the same streams (same codecs, same time base, etc.).
Here is an example of how you can do it (each video file should end in ..-01.avi
, ..-02.avi
, etc..):
First, create a file that contains the list of all your .avi files. You can do this manually, but if your files are named in a sequence like 01.avi, 02.avi, 03.avi, and so on, you can generate this list automatically using a bash command. Here's how you can do it: