Latency problem


I’m using Ardour 3 Beta 5 under Fedora 17 and have a problem regarding latency: I have two MIDI-tracks. One for the snare- and one for the kick-drum. The snare-track has a LinuxSampler-plugin whose audio output is connected to Ardour’s master-in. The kick-track is connected via JACK-MIDI to ZynAddSubFX. Zyn’s audio-outputs are also connected to Ardour’s master-in.

If I increase the JACK’s buffer-size during mixing to avoid buffer-underruns, both tracks have a different latencies! Don’t know if the snare or the kick comes earlier, but both don’t fit together rhymically. How can I avoid this?

Thanks in advance.


I don’t think we’re supposed to talk about A3 here in the forums.

If it were my project, I’d just record the kick and snare to audio tracks. Those tracks could then be nudged into perfect sync, and would not be affected by the JACK latency. It would also mean that I had fewer things to worry about while mixing.


I don’t think it’s a bug in A3 so I think it’s OK to discuss it here. I think it is caused by the round-trip of MIDI- and audio-data. But how to prevent it? Recording every single track really doesn’t fit well into my workflow… Any other suggestions?

Does no one have any idea?

Sorry for the big amount of typos above… :wink:

Thanks for your message. I restarted everything to change the buffer size. But I’ll wait for Ardour 3 final before experimenting again on this…


We aren’t supposed to talk about A3 here at all. but anyways…

A question, are you changing the buffer size on the fly or restarting jack… If you are doing it on the fly then don’t … try doing it be restarting jack to ensure that the apps actually register the change.

Next thing I would do is connect the outputs of your plugins back to the inputs of an audio track, not to the master in… Then at least you can mix those sounds better, visualise them and see where the problem might be.

I don’t know if that would solve your problem… this could be an issue with Jack (MIDI or audio), or an issue with one of the other apps.

As a test you could sample your kick sound out of Zyn and input it into linuxsampler. Then drive both sounds out of Linuxsampler… that will isolate whether Ardour has an issue sending the MIDI or if it is in one of the external paths. If it is with Ardour… submit a bug on Mantis… follow all the normal procedures… and make sure you detail a repeatable test…

If they are the same, then you need to identify which app is delayed (easiest done by sending both instruments a 4/4/ kick and recording, then you will see clearly which instrument is delayed)… and hit up the mailing list for that app.