standard AVI files use internaly 32 bit pointers. One can address a maximum of 4GB using 32 bit pointers. Such files originally had SOFTWARE based limits of 1GB at the begining ( all MCI based software ), 2GB (Video for Windows oriented software) and today the theoretical maximum of this kind of avi files is 4 GB by using DirectShow based software or software which is using it's own code for reading and writing avi files.