Stochas just produces silence with LMMS and Carla

[DaveyBoy1970]

I'm not sure this is bug as such, and is probably a feature request.

I'm trying to use Stochas within Carla patchbay with LMMS under Ubuntu. It works beautifully with playback, however when it comes to exporting the finished track, all Stochas-derived notes are ignored and the track is just silent. The problem is the same with both the Linux and Windows VSTs (using the Wine bridge).

I thought that it was just a failing of either the Linux interface or some other interface in LMMS and I've reported it to them. But I've discovered that BlueArp works just fine, albeit requiring the wine bridge - and so far it seems that is the only note-generating plugin that does work. While BlueArp is very powerful and useful, I would love to use the probabilistic nature of Stochas as I'm trying to create very long generative pieces.

I realise this issue probably affects just me, but is there anything that can be done?

[baconpaul]

I wonder if stochas is even generating midi when doing the render. Like: I wonder if transport isn't toggled 'on' in lmms when exporting.

[rudeog]

@DaveyBoy1970 is there a way you can export 'in real time'? Not sure if this option exists in LMMS. I know in Reaper this is called 'Online Render'.
FWIW in Reaper the offline render works fine for Stochas. As @baconpaul suggests, maybe LMMS is not turning on transport during render.

[DaveyBoy1970]

Fast response! I think you're probably right. Is there any way I could check that?

[baconpaul]

(it might also be carla not communicating transport but that's less likely).

if you have dev skills, if you can build stochas from source you could put a print statement in. could point at a few likely spots if you want.

[rudeog]

Hmm, I have not used LMMS and dont have a way to test it. I did a quick search and didn't turn up anything.
One thing you could try is, if you are able to record output midi from stochas to your track, then the midi should exist in your project and you could disable stochas while exporting. Although I am not sure whether this would be supported either. Is there a way to route midi from one track to another? if so you might try that and recording the midi on the latter track.

[DaveyBoy1970]

The only way I can export in real time is to record the playback with something like audacity. That works up to a point, but if a synth decides to get heavy-handed with the processor I end up with clicks in the recording.

Like I said, I was originally putting this down to a failure in LMMS but BlueArp works perfectly and that should use a similar method? (I'm starting to get out of my depth lol)

[DaveyBoy1970]

@rudeog - You can only export midi from LMMS - I don't think it can do a rel time MIDI recording.

I have tried routing the MIDI to different tracks, but it doesn't seem to do anything and LMMS usually crashes.

[rudeog]

I found this video which is not doing exactly what we want, but might help get there: https://www.youtube.com/watch?v=uxZcunifT6w&ab_channel=KrisOcchipinti
Look around 5:19 where he is linking output midi from a track to input midi on another track. If you were to try that, and then arm that second track for recording, it should hopefully record the midi output from Stochas which would hopefully be sent from the first track (apologies if this is what you already tried above). This would rely on LMMS outputting midi from the VST as opposed to just outputting the midi piano roll.
Failing that, you could try some kind of external midi loop back program (not sure if that exists), and in that case, you'd send midi out to it (as he goes over earlier in the video with amSynth) and then bring it back in. It starts getting pretty inconvenient at that point though I guess.
As Paul said earlier if you are able to do a linux build we could direct where to put some log messages which might indicate where the problem is (either LMMS or Stochas).

[DaveyBoy1970]

Great. I'll try that this evening. I think I might have tried it already in my fiddlings, but it's better to follow a demonstration.

I wasn't intending on doing a build, but I will be starting afresh on a new PC soon, so maybe that would be the time to do such a thing. I'm not incredibly adept with code but I can follow instructions.

[DaveyBoy1970]

Well I had a go at it.

In carla I had Stochas and the MIDI simple filter going in a chain to the MIDI output (tried various channels). MIDi data was definitely going through because the keys on the indicator keyboard in the MIDI filter were lighting up.

I mapped the MIDI channel to another track with a plain synth - nothing fancy. When I added a note to the piano roll on the track Stochas was connected to, it played on the mapped track. Starting playback, the Stochas track played, but the mapped track was silence.