Converting AVI encoded file with an IMM5 codec
If all else fails, you can try Virtualdub: http://virtualdub.org/ It offers the option to export to a series of BMP files, which you can then stitch together using a more common codec.
Did some googling, and IMM5 seems like a pretty obscure format, possibly without open-source implementation, too.
How about (and this is really the last option) using a desktop recorder tool (Fraps, VLC - yes, it can do that too.) and recording the video as it plays in that "BackupPlayer"? Since it's CCTV footage, it's probably low-resolution and framerate anyway, so you shouldn't have any noticable quality loss when doing that.
This obscure format seems to be produced by a number of DVRs that use the Infinity encoding chip. The references that I have found relate to the IMM4 codec, but may still be worth trying.
The article IMM4 Codec and MEncoder describes how the author converted IMM4 video to other formats, so my advice is to read it carefully. The codec was found to reside in VCMIMM4.dll, which would still probably need to be registered with regsvr32.
MPlayer counts IMM4 among its supported formats and may install the codec, as also explained in the above article.
I have found a download on the cctvone.com website that seems to have an installation file for the IMM4 codec, found here and again here. I have no personal experience with that website.
There may also be some connection between the IMM codec family and the GeoVision CCTV MPEG4 Codec, so you might try installing that as well.
FFmpeg now has a decoder for files encoded with the IMM5 codec. It is not in a released version yet so in order to use it, you will have to build it from the master branch.
It was added on August 29th in this commit
See this blog, too:
https://spreadys.wordpress.com/2013/05/18/portable-smplayer-with-fjht-imm4imm5-and-imm6-codecs-included/
the link is taken from this reddit thread:
https://www.reddit.com/r/techsupport/comments/1un7cx/converting_this_imm5_avi_file_into_something/
In particular, I've installed the mm4,5 and 6 codec and played the video with Windows Media Player successfully.