Thanks a lot for your quick replay!
> In case of the field "tcp.analysis.retransmission" I think there
> is room for improvement. Even when this field is in the packet, no
> output is given. That is because this field does not have a value.
> It is either present or not.
Is this because it's type is 'None'? I'll open a bug, but I would also
like to be able to fix this myself, I just don't have an idea where.
Using filters currently is not an option, since I want to parse the
output of multiple fields automatically. With filters I would have to
run multiple instances of tshark AFAIK.