Hi Nadine,
The videos do not need to be in chunks of 1000 so a single large uncompressed .avi file should work. The timestamp file is only needed for syncing the Ca2+ data to behavior. When extracting dF/F traces the script will require timestamps but you can generate these by running something like ms.time = linspace(0,ms.numFrames*1000/30,ms.numFrames); where 30 is the framerate the scope was running at.
We are in the process of switching over to a new analysis pipeline using CNMF. I would suggest you look into that as well.