[LAD] LV2 input buffer problem in ardour

hi *! whatever i do, i can't seem to get any data from an audio input port in my lv2 plugin. i made local copies of all buffer pointers (even though that shouldn't be necessary iirc), and in case ardour does in-place processing, i always cache sample N before writing it to the first output, so that i still have it available for the other outputs. i even set lv2:inPlaceBroken, but no luck. now i was beginning to suspect i'm very very stupid, but then i installed the eg-amp.lv2 plugin (the simple amplifier example from the lv2core repository, which i've used as a template for my own code), and hey presto: no signal either. what the fu..ndamental problem might be, i can't say. any insights most welcome. thanks, jörn