I was wondering if it is possible to change the filter used to write to or read form a file without closing/reopening the file? The usecase is reading/writing matlab files, which contain zipped blocks within a context of unzipped data. So I would need to be able to switch on compression once such a block starts and switch off afterwards, and it would be nice not to have to ftell/close/create appropriate stream/open/ fseek every time. Best Daniel