So here I am, after days and nights of inefficient efforts.
It seems I face two different problems, one being perhaps able to solve the second.
First one, when I use mimicdecoder. In console, I get a :
[probe_ffmpeg.c] critical: unable to open '/dev/stdin' (libavformat failure)
(...)
mimic2rgb: End of file. 21.14 fps, CFT: 0:00:07, ( 0| 0|20)
[decoder.c] cancelling the import threads0:00:10, (16| 0| 4)
[transcode] encoded 42 frames (0 dropped, 0 cloned), clip length 10.50 s
So it looks like something is broken in my ffmpeg/libavformat install. But I dunno what. I changed from libavformat-extra-52 to libavformat52, without any success. Installed many -dev packages, without any success.
I've no idea how to solve this one...
Which, once solved, could perhaps - or not :/ - transform my .cam in .avi *_*
That brings me to my second problem :
Using many other "cam to avi" possibilities (Mobile Media Converter, AviDemux, VLC,...), I can transform some other old .cam files into .avi files.
But some files, including the one I need to get in avi, are somehow corrupted. What sounded strange to me, was that aMSN log viewer was perfectly able to read them.
So I investigated a bit, and got these results :
1) aMSN has one file for one month logs, per e-mail address of course.
2) Inside the log viewer, we have the different days and hours of every cam session of the month. I guess this is related to the .dat (index?) file that's created with every .cam file.
3) In this very case, every other transcoder fail after 8 seconds.
4) Inside aMSN log viewer, I realized that if I started the viewing from the very beginning, after those 8 seconds the viewer also fails to show the movie (it suddenly stops, and the little cursor move from the beginning of the bar to its end).
5) But I never suffered of that before, because those first 8 seconds are of no interest, so I always pointed the cursor a few minutes later.
6) So it seems aMSN, even if it fails to read when it starts from the beginning, is able to display the rest of the movie if we don't go through this damned 8th second.
7) So perhaps is it any way to "cut" the .cam file after 10 seconds? Or if I can cut it into different files, every one of them being a different cam session, as aMSN shows them? Unfortunately, avidemux and every prog' I could think at weren't able to even open the .cam file.
But bay me one of those amsn genius would have a brilliant idea on how to do so

?