Setting up Ardour/JACK on Mint/Ubuntu

# Full context I would like to set up Ardour and mess around a bit on a keyboard-as-in-music which I got a while ago, turned out not to need, but couldn't return. When I try to start Ardour, with a new session testing, using JACK as the audio system, I get (on starting JACK) the warning: WARNING: Your system has a limit for maximum amount of locked memory. This might cause Ardour to run out of memory before your system runs out of memory. You can view the memory limit with 'ulimit -l', and it is normally controlled by /etc/security/limits.conf` When I try to continue on from there (because I don't expect to be using much memory on it any time soon, since right now I just want to be able to make any sound at all), I get the error error Could not create session in "/home/qwertystop/multimedia/ardour/testing". When I try to start JACK through Qjackctl (with verbose messages on), it either apparently starts (but does not, as far as I can tell, register any input from my keyboard) or pops up its logs to report a failure. In the latter case, scrolling back through them, I found an entry saying that the audio device was already in use, or something similar. That hasn't popped up in a while, I don't think I did anything differently between attempts, and unfortunately I did not copy down the exact log message the last time it did come up. I know it isn't (purely) a matter of whether any other applications are playing audio. If I click Close instead of OK from the Ardour config, I get Could not create session in "/home/qwertystop/multimedia/ardour/testing": Cannot connect to audio/midi engine. I have: - One "USB-MIDI keyboard controller" (Alesis V25) - Built-in audio on motherboard (not connected to any I/O, but does exist and occasionally confuses applications) - Audio output over HDMI from GPU - Linux Mint - Ardour 4.6 (via apt) - jackd 1.9.11 (installed as dependency of Ardour) /proc/asound/cards has: 0 [PCH ]: HDA-Intel - HDA Intel PCH HDA Intel PCH at 0xdf240000 irq 128 1 [NVidia ]: HDA-Intel - HDA NVidia HDA NVidia at 0xdf080000 irq 17 2 [V25 ]: USB-Audio - V25 Alesis V25 at usb-0000:00:14.0-1, full speed ~/.jackdrc had /usr/bin/jackd -v -dalsa -dhw:0 -r44100 -p1024 -n2 the first time I looked, but when I opened Ardour it changed to /usr/bin/jackd -t 200 -p 2048 -R -T -d alsa -n 2 -r 44100 -p 1024 -d hw:PCH,0 -X raw. I tried changing PCH to Nvidia but it didn't help; Ardour changed it back and the other devices don't show up in Ardour's config stuff. Pulseaudio does exist on my system and is currently running. I tried pasuspender qjackctl but JACK still wouldn't start. I also added myself to the audio group, following this , which seems to have stopped it from hitting memory errors. ------------- # Current status The log from the most recent attempt (after adding myself to audio group, running qjackctl through pasuspender, driver is alsa, interface is hw:NVidia) is: 20:13:47.156 Statistics reset. 20:13:47.162 ALSA connection change. 20:13:47.172 D-BUS: Service is available (org.jackaudio.service aka jackdbus). Cannot connect to server socket err = No such file or directory Cannot connect to server request channel jack server is not running or cannot be started JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock 20:13:47.245 ALSA connection graph change. 20:13:52.295 D-BUS: JACK server could not be started. Sorry Cannot connect to server socket err = No such file or directory Cannot connect to server request channel jack server is not running or cannot be started JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock Wed Jan 2 20:13:52 2019: Starting jack server... Wed Jan 2 20:13:52 2019: JACK server starting in realtime mode with priority 10 Wed Jan 2 20:13:52 2019: self-connect-mode is "Don't restrict self connect requests" Wed Jan 2 20:13:52 2019: Jack: JackPosixThread::StartImp : create non RT thread Wed Jan 2 20:13:52 2019: Jack: JackPosixThread::ThreadHandler : start Wed Jan 2 20:13:52 2019: Jack: playback device hw:NVidia Wed Jan 2 20:13:52 2019: Jack: capture device hw:NVidia Wed Jan 2 20:13:52 2019: Jack: capture device hw:NVidia Wed Jan 2 20:13:52 2019: Jack: playback device hw:NVidia Wed Jan 2 20:13:52 2019: Jack: apparent rate = 44100 Wed Jan 2 20:13:52 2019: Jack: frames per period = 1024 Wed Jan 2 20:13:52 2019: Jack: JackDriver::Open capture_driver_name = hw:NVidia Wed Jan 2 20:13:52 2019: Jack: JackDriver::Open playback_driver_name = hw:NVidia Wed Jan 2 20:13:52 2019: Jack: Check protocol client = 8 server = 8 Wed Jan 2 20:13:52 2019: Jack: JackEngine::ClientInternalOpen: name = system Wed Jan 2 20:13:52 2019: Jack: JackEngine::AllocateRefNum ref = 0 Wed Jan 2 20:13:52 2019: Jack: JackPosixSemaphore::Allocate name = jack_sem.1000_default_system val = 0 Wed Jan 2 20:13:52 2019: Jack: JackEngine::NotifyAddClient: name = system Wed Jan 2 20:13:52 2019: Jack: JackGraphManager::SetBufferSize size = 1024 Wed Jan 2 20:13:52 2019: Jack: JackConnectionManager::DirectConnect first: ref1 = 0 ref2 = 0 Wed Jan 2 20:13:52 2019: Jack: JackGraphManager::ConnectRefNum cur_index = 0 ref1 = 0 ref2 = 0 Wed Jan 2 20:13:52 2019: Jack: JackDriver::SetupDriverSync driver sem in flush mode Wed Jan 2 20:13:52 2019: Acquired audio card Audio1 Wed Jan 2 20:13:52 2019: creating alsa driver ... hw:NVidia|hw:NVidia|1024|2|44100|0|0|nomon|swmeter|-|32bit Wed Jan 2 20:13:52 2019: ERROR: ALSA: Cannot open PCM device alsa_pcm for playback. Falling back to capture-only mode Wed Jan 2 20:13:52 2019: Jack: JackDriver::Close Wed Jan 2 20:13:52 2019: Jack: JackConnectionManager::DirectDisconnect last: ref1 = 0 ref2 = 0 Wed Jan 2 20:13:52 2019: Jack: JackGraphManager::DisconnectRefNum cur_index = 0 ref1 = 0 ref2 = 0 Wed Jan 2 20:13:52 2019: Jack: JackEngine::ClientInternalClose ref = 0 Wed Jan 2 20:13:52 2019: Jack: JackEngine::ClientCloseAux ref = 0 Wed Jan 2 20:13:52 2019: Jack: JackGraphManager::RemoveAllPorts ref = 0 Wed Jan 2 20:13:52 2019: Jack: JackPosixSemaphore::Destroy name = jack_sem.1000_default_system Wed Jan 2 20:13:52 2019: Jack: ~JackDriver Wed Jan 2 20:13:52 2019: ERROR: Cannot initialize driver Wed Jan 2 20:13:52 2019: Jack: no message buffer overruns Wed Jan 2 20:13:52 2019: Jack: JackPosixThread::Stop Wed Jan 2 20:13:52 2019: Jack: JackPosixThread::ThreadHandler : exit Wed Jan 2 20:13:52 2019: ERROR: JackServer::Open failed with -1 Wed Jan 2 20:13:52 2019: Jack: Succeeded in unlocking 82274202 byte memory area Wed Jan 2 20:13:52 2019: Jack: JackShmMem::delete size = 0 index = 0 Wed Jan 2 20:13:52 2019: Jack: ~JackDriver Wed Jan 2 20:13:52 2019: Jack: Succeeded in unlocking 1186 byte memory area Wed Jan 2 20:13:52 2019: Jack: JackShmMem::delete size = 0 index = 1 Wed Jan 2 20:13:52 2019: Jack: Cleaning up shared memory Wed Jan 2 20:13:52 2019: Jack: Cleaning up files Wed Jan 2 20:13:52 2019: Jack: Unregistering server `default' Wed Jan 2 20:13:52 2019: ERROR: Failed to open server Wed Jan 2 20:13:54 2019: Saving settings to "/home/qwertystop/.config/jack/conf.xml" ... 20:13:54.478 Could not connect to JACK server as client. - Overall operation failed. - Unable to connect to server. Please check the messages window for more info. Cannot connect to server socket err = No such file or directory Cannot connect to server request channel jack server is not running or cannot be started JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock JACK starts if the interface is set to hw:PCH or hw:PCH,0, but I don't have any speakers except on my screen, which is on my graphics card's HDMI, so I'm not sure there'd be any point. Did some more experimentation. Setting the interface to (default) and setting the input and output devices separately was useful. If I set input and output both to NVidia, I get the same ERROR: ALSA: Cannot open PCM device alsa_pcm for playback. Falling back to capture-only mode error as before. If I set one of the two to NVidia and the other to PCH, I don't get an error. However, neither configuration produces audio output from the speakers in my monitor. If output is NVidia and input is PCH, Jack can see readable system ports presumably matching the mic ports, but no writable system ports. If output is PCH and input is NVidia, Jack can see writable system ports for my headphone jack but no readable ports. This is consistent with the idea that JACK cannot interface with the NVidia device for... some reason?