Native synths crackle on arpeggios

[depretux]

Hi all

I'm using lmms 1.1.3 from the kxstudio repos on debian wheezy amd64, on top of a core2duo T6400, 2Ghz
Most apps, both audio and midi work alright on this setup, either under jack or alsa. However lmms seems to eat too much CPU for anything regarding audio processing.

I'm currently interested in using the lmms arpeggiator, so I for example set up the arpeggiator in the tripleosc plugin, and use my midi keyboard to control it. Everything works ok until I lower the time settings too far, or if I fire many voices at the same time. In those scenarios, the cpu usage meter spikes and audio starts to crackle. This happens under the alsa, jack and sdl backends, with varying frame buffer settings.

This happens with every lmms' native plugin that I have tried.

I was wondering if this problem was part of lmms' audio section or if midi was involved: I used the arpeggiator to drive an external standalone synth (amsynth) and no matter how low the time or gate settings were set, or if I had a dense 'stacking' setting, cpu usage remained stable.

I know the native synths might be a little bit intensive on the cpu, but the spike don't seem linearly corelated to the amount of voices I'm using.

I really don't have a clue on where to start troubleshooting this (or how to properly fill a bug report) but just let me know of anything that can be done to help.

Thanks a lot!

[musikbear]

normally lmms plays arps with native synths with no problems.
Could you make a file with this problem and upload it?

[depretux]

Thanks for your answer, I've solved the issue.

I usually run jack with a -p128 -r48000 setting, but lowering the sample rate to 44100, and setting lmms to a frame buffer of 1024 (while keeping jack at 128) gave me a working set up.

I can now arpeggiate at 1/32nd with a 140bpm with most synths, and It wont crackle.

I don't feel any extra latency, so I guess the lmms frame buffer is ignored when running on jack

[musikbear]

Nice to know that it is solved!