Maybe I have misunderstood how things work, or I'm using too old version of jack, but here's what happens: 1. Start jack 2 (jack-audio-connection-kit-devel-1.9.9.5-1.fc17.x86_64) 2. Press the "Start transport rolling" button in qjackctl. 3. Qjackctl reports "Rolling" in the display. 4. Create jack client 5. Call jack_transport_query(client, NULL). 6. jack_transport_query(client, NULL) always returns JackTransportStopped Shouldn't jack_transport_query(client, NULL) return JackTransportRolling? (It doesn't matter whether I activate the client or not before calling jack_transport_query(client, NULL)).