[Jackaudio] Get raw pcm from jack port

I've been trying to find a good way to a stream of audio from jack into opusenc (the official opus encoder tool) and then pass it to something like oggfwd to send to Icecast. However, a few different things I've tried in python haven't worked out, and I'm trying to not have to rely on an "audio file player" (like sox or pyaudio) to sit in the middle. Now I'm wondering if there's a way I can get the raw pcm data from jack. Is this possible? Is there an existing tool?