Get offset position to find varying metadata#23

In scanimage files, every frame as a `Software` field. But all of them point to the same offset at the beginning of the file (32 for me). Is there a way to get the position of the field for a given frame so that I can know if my metadata are read from different places or not? Basically I would like to access to `fpos` found in tiffread31_readtags.m L356 but I don't know how to do that from a stack. I'm not sure if it would be a really useful feature outside of this only use case (in which case I could simply always load the first `Software` and ignore the rest)