Thanks Nick! Will take this into account.

I've stumbled over another question in the meantime:

It seems to me that after the call to set_encoding(), self._snapshot contains the decoder flags from the state of the *old* decoder. On the next call of eg. tell(), the flags from the old decoder are then passed to setstate() of the new decoder.

Isn't this a problem? I thought the flags could mean different things to different codecs.