I had a simular problem with the IMM4 codec.
We had an .avi file built using IMM4. It was delivered to us by a law firm that needed the file converted for playback in court.
When I ran the file through Gspot. Gspot reported the codec used was indeed IMM4 and the "DVR system AVI builder on DSP"
I used google to look up what that meant and best I could tell was the AVI was built by a digital video recorder from a door security protection system.
After calling around I found the system used was the Lorex L23WD Series Security DVR.
Lorex has a download for the IMM$ codec on their website. It is sneeky because it says downlaod codec for L23 Series Security and not IMM4 codec.
http://www.lorextechnology.com/Complete ... Location=+