I’m running Ardour 6.5.0 with JACK (Qjackctl) on Linux Mint 19 (64bit). Experiencing frequent crashes that are making Ardour essentially unusable, they happen the moment I open my projects. Otherwise, while producing quite often the playhead disappears and playback stops, and refuses to start again — where earlier I had the playhead following my mouse, now it is nowhere to be seen. In all these cases, Qjackctl tends to display a message along these lines:
subgraph starting at ardour timed out (subgraph_wait_fd=9, status = 0, state = Running, pollret = 0 revents = 0x0
Recently, when this happens, I open Window > Audio/MIDI setup and try to reconnect to JACK. It doesn’t tend to work out, and I get this output in the Ardour log:
2021-01-26T12:53:21 [ERROR]: VST '/usr/lib/vst/mod-harmonizer.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-harmonizer.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/Harmonizer'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/Harmonizer'
VST '/usr/lib/vst/mod-drop.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-drop.lv2.so': failed to load cache file.
VST '/usr/lib/vst/mod-drop.lv2.so': Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/Drop'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/Drop'
VST '/usr/lib/vst/mod-capo.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-capo.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/Capo'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/Capo'
VST '/usr/lib/vst/mod-superwhammy.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-superwhammy.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/SuperWhammy'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/SuperWhammy'
VST '/usr/lib/vst/mod-2voices.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-2voices.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/2Voices'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/2Voices'
VST '/usr/lib/vst/mod-harmonizercs.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-harmonizercs.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/HarmonizerCS'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/HarmonizerCS'
VST '/usr/lib/vst/mod-supercapo.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-supercapo.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/SuperCapo'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/SuperCapo'
VST '/usr/lib/vst/mod-harmonizer2.lv2.so': [WARNING]: Cannot get VST information for '/usr/lib/vst/mod-harmonizer2.lv2.so': failed to load cache file.
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#fixedBlockLength' in 'http://moddevices.com/plugins/mod-devel/Harmonizer2'
Unsupported required feature: 'http://lv2plug.in/ns/ext/buf-size#powerOf2BlockLength' in 'http://moddevices.com/plugins/mod-devel/Harmonizer2'
JACK: zombified - calling shutdown handler
2021-01-26T12:53:40 [ERROR]: JACK: zombified - calling shutdown handler
Finally, when such crashes occur I often get a message box that reads: “Ardour is not connected to any audio backend. You cannot open or close sessions in this condition.” What’s happening here? Thanks for the help.
To be honest the technicalities of JACK audio etc. really confuse me. (I’m just a kid who makes beats!) I thought you have to use JACK to run Ardour but have just figured out that I can run it with my built-in pulseaudio too? It seems to run alright with pulseaudio for now, but I’ve been switching to JACK when I need to use my USB mike, because I can’t seem to find the mike input in Ardour’s routing when using pulseaudio. So I have a few questions in response to @x42 :
How do I check my JACK audio version? Is jack2 an update to jack1?
If so, how do I switch between jack1 and jack2 on qjackctl?
Is it possible to configure pulseaudio to work with a USB microphone as a workaround while I fix my JACK issues?
I don’t understand what “zombifying” means… what’s happening when JACK “zombifies”?
In general we recommend to prefer Ardour’s built in ALSA backend (Pulseaudio is playback only).
Do you use different devices for input and output? Record from USB-microphone input, play to PC’s soundcard? If so that may explain the issues you’re seeing with jack.
You don’t. you uninstall jack1 and install jack2 instead (or vice versa) using your distro’s package manager.
See above, prefer Ardour’s ALSA backend. It even performs a bit better than JACK and is also more robust in case you need MIDI.
You only need JACK if you want to share the soundcard with other JACK applications, or use other JACK apps alongside with Ardour.
(historically, before 2013, Ardour required JACK, and a lot of tutorials out there have still not caught up). Pulseaudio is not reliable for production, Ardour only supports it for convenience.
In modern computers that are processing realtime audio (using a program like Ardour), every few milliseconds the program has to do a bunch of work (reading, writing, transforming samples to/from the audio hardware). There’s a deadline for this work, and if the program doesn’t get it done in time, the user will hear clicks and skips and pops (we call them “xruns”).
If the program is using JACK to move audio data to/from the audio hardware, JACK is aware of when a program takes too long to get its work done. Since there’s no sensible way to get the program to “go faster” or “do better”, JACK simply stops telling the program that it has work to do.
In more technical terms, the program forms part of a “graph” of nodes, each of which is responsible for processing data (with only 1 program - like ardour - there are just 2 nodes, JACK and the program), and JACK’s decision is described as “removing the application from the graph”.
But to make things shorter, we call this “zombifying” the program, or “zombification”. The program is still alive from the perspective of the computer and the user, but JACK will no longer tell it do any work, or give it any data or ask for any data from it.
Firstly, thanks so much for the replies, this helps me understand a lot!
Do you use different devices for input and output? Record from USB-microphone input, play to PC’s soundcard? If so that may explain the issues you’re seeing with jack.
When using my USB mike I usually output through the mike’s connected headphones as well. However they appear as slightly different devices in Qjackctl > Advanced > Input and Output: one appears as “USB Yeti Stereo Microphone,” the other as “USB Audio Device” or something. My output for jackd --version is
jackdmp version 1.9.17 tmpdir /dev/shm protocol 8.
Pulseaudio is playback only
Oh, so is this why I don’t get any input options when using Pulseaudio?
we call them “xruns”
I’m getting a bunch of these! I had to go to preferences and stop Ardour from creating markers everytime an xrun happens, because I was having to manually delete all of them (one every other second or so). Is this related to the I/O discrepancy mentioned above?
That may explain things. With JACK, this advanced config should only be used with devices that have a common sample-clock (e.g using hardware word-clock sync). Otherwise you’ll get dropouts. xruns galore!
If you want to use jack, have a look at https://jackaudio.org/faq/multiple_devices.html
in short, start jack in playback only more, and add the input device using alsa_in (or zita-a2j from zita-ajbridge)
