Connect software to jamulus via JACK with different buffer size and sampling frequency

[vocobox]

I am trying to send sound generated by a software synthetizer to a Jamulus session. As pointed by @trebmuh in https://github.com/corrados/jamulus/issues/82, JACK is a good choice for that. However, it seams that JACK is not able to deal with a sound consumer and producer with different buffer size or sampling frequency. Did anyone achieved to send software sound to Jamulus via JACK?

Here's my post on JACK issue list. I unfortunately get no answer.

I am trying to use Jack 2 (0.92_B3) on MacOS 10.12.6 to send audio from an Arturia drum machine (the producer) to Jamulus (the consumer). I ran JackPilot and wonder if it can be used to share audio content between applications with different audio settings.

Connecting the sound producer to Jack

• Each time I try to select Jack in Spark device list, Spark display an error message : "Couldn't change buffer size". I tried all buffer size setting in Jack without success. How can I guess the expected buffer size on the producer application? Is it possible to let Jack adapt to it? Spark does not display sampling frequency and buffer size until the device is loaded.

Connecting the sound consumer to Jack

• At the beginning Jamulus threw an error asking for 48KHz sampling frequency. This halted the Jack server with an error popup, so I restarted the Jack server with 48KHz setting.
• When trying to select Jack as input in Jamulus, JackPilot pops another error : "Another application has changed the sampling rate" which is surprising, since the two applications where both on the same sampling rate.
• Then restart Jamulus and Jack with 48KHz, it is fine. Will Jack be able to resample from consumer to producer sampling rates automatically?

NB : Hog mode is off.

[jkbd]

If you start a JACK-Server, you set sample-rate, buffer size of the cycle and the number of buffers. Audio-applications should adapt to these settings. Theoretically applications should be capable of running with dynamically changing cycle size, so only sample-rate should be a concern.

From my understanding so far, Jamulus uses 48kHz sample-rate, because the OPUS codec does not support 44.1kHz. JACK is not meant to resample frame-rates between applications. Resampling would have to be implemented in Jamulus.

I don't know about macOS and JackPilot quirks. Please try to make sure, that no program tries to reconfigure or override JACK settings.

[corrados]

What do we do with this issue here? Jamulus needs 48 kHz but it should be possible to use any buffer size.

I think this is about Jack audio and not Jamulus. Maybe we should close this issue?

[vocobox]

Yes, thanks for asking.