Target sample rate not known outside the flowgraph
This is an old issue and perhaps not often needed, but the fact that the different flowgraphs calculate the target sampling rate inside and is not available to the pre-/post scripts is a challenge for the external tools (and I/Q recordings for now).
I have made a small script that tries to predict this but it is manually updated when the calculations change or new flowgraphs are added. I think it could at least be integrated into observer.py with the variable replacement, like {{SAMP_RATE}}.
It will also be needed to put in to the metadata for SigMF.