[LAD] Looping audio to oneself via Jack

Fred Gleason fredg at paravelsystems.com
Tue May 3 22:20:33 UTC 2011

Howdy Folks:

Here's a seemingly trivial requirement that has me stymied: I have a Jack client (external, built against 0.102.20) where it occasionally makes sense to connect an output port to an input on the same client.  QJackCtl happily makes the connection; the process callback delivers data as expected, but it's all zeros for the connected input port!  I can route the same client output port to a physical output (ALSA backend) and hear the expected audio.  Likewise, a physical capture port connected to the input on the client receives data from the card as expected.  It's only the "loopback" within the same client that doesn't want to go.

At first I suspected that the JackPortIsTerminal flag might have some bearing on this, but changing this value seems to have no effect.  Am I missing something blatantly obvious here, or is this something that is just not within the scope of Jack to allow?

Any pointers greatly appreciated.


| Frederick F. Gleason, Jr. |               Chief Developer               |
|                           |               Paravel Systems               |
|  ...one of the main causes of the fall of the Roman Empire was that,    |
|  lacking zero, they had no way to indicate successful termination of    |
|  their C programs.                                                      |
|                                            -- Robert Firth              |

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