For a few days, RadioBook had a DMR tab — tune in to a BrandMeister talkgroup and listen to live traffic, right in the app. It worked. Then it got pulled back out. Here's the whole story, because I'd rather be straight about it than just have it quietly disappear.
Why listening was possible at all
DMR's actual over-the-air voice codec, AMBE+2, is patent-encumbered — that's what killed an earlier attempt at building a transmit-capable DMR app entirely. But listening turned out to be a different problem: BrandMeister runs a public service called Hoseline that does the real AMBE decode server-side and streams back plain, patent-free μ-law audio to anyone's browser. Nothing about that half was ever in question — I even verified the audio math byte-for-byte against the standard decode algorithm before writing a line of app code.
The wall
What I didn't check closely enough going in: whether a client other than BrandMeister's own web page was actually welcome to connect. It isn't. Their Hoseline endpoint rejects any request that isn't their own website — confirmed by testing it directly, not just inferred. Every non-browser client I tried got the same flat rejection, and that's consistent with what happened when the app itself tried it too.
There's no public developer program to request access from, either — I checked their actual documentation site before suggesting anything, and the "Developers" section of their own docs is an empty stub marked "work in progress."
Where it stands
The DMR tab is hidden from the app's menu for now. All the code — the protocol client, the audio decoder, the talkgroup import — is still there, just not reachable, in case that ever changes. If you want to see it work, the honest path is asking BrandMeister directly whether they'd allowlist a specific app; that's not something I can do on anyone's behalf.