LinuxMusicians

Disclaimer: I am not a musician, though I very much appreciate that art form.

My interest in Carla as a plugin host stems from a non-production application. It most closely might resemble live performance, as it is geared toward sound reproduction, but in a purely playback scenario: I want to host Windows-based VST plugins for bass management and Dirac Live processing for 7.1 and stereo audio for use in a home theatre / stereo listening environment.

I currently have an odd mish-mash of equipment to do this, forgoing the traditional "kitchen sink" A/V preamp with features I don't want or need at a price I'd rather not pay, and lacking the flexibility I want. I am taking an HDMI signal from an "audio only" HDMI 1.4 port on a 4k bluray player (basically, black video and 7.1 LPCM audio, decoded in the player), running it through a miniDSP nanoAVR for bass management, then a nanoAVR DL for Dirac Live room correction, through an HDTV supply HDMI to SDI converter (that strips HDCP, shhhh!) and deembedding 48 kHz LPCM audio using a Blackmagic SDI to audio deembedder to give me four sets of two channel audio via AES/EBU. This drives the DAC portion of an old Lucid ADA 8824 AD/DA 8 channel converter, and four amps (Crown XLS 1502 for front left and right, Crown XLS 1002 for side surrounds, Crown XLS 1002 for read surrounds, and an Outlaw Audio M-2200 for center), and two Klipsch 12" subs for LFE, and redirected LF. Main speakers are Bohlender-Graebner Radia 520i fronts, 220i center, and PD6-LCRi surrounds.

Volume control is handled digitally in one of the nanoAVRs, thought the Lucid 8824 sports VCAs on all 8 channels, that I could control with a small single board computer and a USB to MIDI interface. As long as I don't go too low, it works well enough: I can reach THX reference levels in my 14'x12'6"x8'6" room.

I could certainly upgrade the old Lucid 8824 to an Octo DAC8 Pro, and the left/right amp to something like a Benchmark AHB2 if I wanted to get serious about stereo.

What I would LIKE to do is eventually replace the nanoAVRs with a single board PC running Carla with bass management and Dirac Live plugins (Windows VST hosted in the Windows on Linux plugin manager), and either do volume control there, or in the Octo DAC. A software-defined audio preamp, if you will. The HDMI to SDI to deembedding hack also limits me to a 48 kHz sample rate. That probably does not matter in a playback environment (with good reconstruction filters), but, as Khan might say, the lack of 24 bit 192 kHz support "tasks me". An Octava HDMI switch modified by JVB digital can get me 4 sets of two channel audio via SPDIF, and a miniDSP U-DIO8 can get that into the PC via USB (and there is an AES/EBU version for output, though both are bidirectional for their respective signal levels and subcodes).

First questions:

1) Can Carla handle more than two channels? I'm guessing it can handle 7.1.

2) Can Carla handle 8 channels of 24 bit, 192 kHz audio input and output via USB under Linux?

3) How stable is Carla hosting Winows VST plugins in a Linux environment? I'd really like to avoid Windows.

I've been playing with Carla under Ubuntu 19.04, but not done much more than use the built-in keyboard to play some of the synths over HDMI to my monitor speakers. I am struggling with the details, for lack of being able to find definitive documentation. For example: I thought I could get Rosegarden to sequence a MIDI file through to one of the synths, but to no avail: I see some plugins (in the patchbay view) have midi inputs or outputs but others have "event" inputs. I am not sure what the difference is.

rlhollan wrote:Can Carla handle more than two channels? I'm guessing it can handle 7.1

Yes. There are different modes. However, a rack mode is only available in 2 channel format, so, in your case it will be necessary to use the “Multiple clients” mode and JACK audio server.

rlhollan wrote:Can Carla handle 8 channels of 24 bit, 192 kHz audio input and output via USB under Linux?

Yes, because it's totally hardware agnostic. Everything regarding that is controlled by JACK, including routing. Routing can be changed in Carla's patchbay interface, but it's still plain JACK routing, not an internal feature.

rlhollan wrote:How stable is Carla hosting Winows VST plugins in a Linux environment? I'd really like to avoid Windows

This depends solely on the plugin itself and wine. Carla is only a host, it doesn't have its own Windows API subsystem. In my experience, it's rock solid handling a multitude of Windows plugs, including some commercial stuff I own. Some plugs just don't start because wine is a reverse engineering product, thus doesn't cover all of Windows API functions, can handle certain apps wrong, etc. A better approach, though, would be searching for Linux equivalents for the plugins you use on Windows. Wine, especially in case with realtime audio, can be quite a resource hog.

rlhollan wrote:I see some plugins (in the patchbay view) have midi inputs or outputs but others have "event" inputs. I am not sure what the difference is

If you were a musician, you'd know that MIDI is designed for realtime applications mainly, so MIDI events are the… MIDI events (Captain Obvious to the rescue), which includes just every MIDI message possible: notes, CCs, patch changes, SysEx etc.

Thanks much.

I am aware that the Carla patchbay is strictly a UI around plugins (or plugin bridges, say Windows VSTs under Wine), that are JACK aware. I probably don't need Carla once I work out my processing sequence (though the Windows VST bridge under Wine might be required).

Unfortunately, one of the VSTs I want to use is a Dirac Live VST that is only available for Windows. I like to avoid Windows like the plague, especially Windows 10: it spys on just about everything you do, even if you configure it not to. I've been led to believe that Carla's bridge to Windows VSTs running under Wine is pretty solid. The other one is a bass management VST, of which there appear to be several. I'm almost tempted to code my own.

I know what MIDI is. In fact, I've used MIDI Sysex commands from a Linux command like to set the VCA levels on my Lucid 8824. (It's the only way to set them: the DACs only have about a 105 dB SNR and 86 dB THD, so the 8824 sports VCAs, similarly "good" VCAs are better than digital volume control, and were common 15 years ago when the unit was still relatively "new".) Had to get a 1x1 MIDI USB interface for that. While playing with Carla, I managed to get the built-in keyboard to play when I highlighted a synth patched to system output, but have not figured how to have it play a track in a MIDI file. The Carla patchbay UI shows MIDI in and out connections as well as event in and out connections. Not sure what the difference is: to me, MIDI commands ARE events, from a software perspective.

I don't think carla has a built in sequencer for playing midi files.

rhollan wrote:Not sure what the difference is: to me, MIDI commands ARE events, from a software perspective.

There is none. Just connect whatever you want and play around. This is most probably related to the fact that some developers like to separate any control inputs from the music related input.

rghvdberg wrote:I don't think carla has a built in sequencer for playing midi files.

But it has MIDI player plugin since 2014, if not even earlier, and this is mentioned on this exact forum. You're misleading.

I wasn't expecting a MIDI player to be built in. I tried installing Rosegarden, but was not able to get it to work despite seeing the JACK connection points in Carla. Probable ignorance on my part, not being a musician as to what is "obvious".

AlexTheBassist wrote:

rghvdberg wrote:I don't think carla has a built in sequencer for playing midi files.

But it has MIDI player plugin since 2014, if not even earlier, and this is mentioned on this exact forum. You're misleading.

TIL that carla has a midi sequencer plugin

rhollan wrote:I wasn't expecting a MIDI player to be built in. I tried installing Rosegarden, but was not able to get it to work despite seeing the JACK connection points in Carla. Probable ignorance on my part, not being a musician as to what is "obvious".

Me neither!
but do you actually need the midi capabilities? I thought we were looking for some complicated audio routing with windows plugins.
Btw, to quickly test if a windows plugin works. Open a command line. Type It will show help message how to run a vst plugin. Very handy.
note, you need to have jack running.

I don't need MIDI capabilities for my final application (audio reproduction through Dirac Live VST in a Windows emulator under Linux running Carla). I was just using it to play with Carla.