LinuxMusicians

danboid wrote:iodelay is working now - thanks for your advice male. The latency varies wildly if Direct Monitor isn't fully set to playback so I obviously didn't check that dial on my first attempt.

I had already done all the tweaks you suggested except my JACK priority is at the 85 default - I'll try upping that soon to see if I can get some more out of it.

Excellent

danboid wrote: I'm presuming the ALSA issue will get fixed eventually. A good first step might be for one of us chickens to report it as broke.

[/quote]

Actually, I'm not sure that it is broke. I borrowed a windows laptop and tried it there: There was also no software mixer in Windows. I think that this device simply lacks software mixer controls since it has a physical volume knob.

I've tried upping JACKs RT priority but still can't run JACK at any lower than 64 without steady xruns, like I get at 32 here. What distro and kernel do you run male? Have you got a sizeable beast of a machine (unlike me)?

I tried my 2i4 out under Windows for the first time at a friends house recently but didn't think to check the mixer options - thanks for pointing that out!

danboid wrote:I've tried upping JACKs RT priority but still can't run JACK at any lower than 64 without steady xruns, like I get at 32 here. What distro and kernel do you run male? Have you got a sizeable beast of a machine (unlike me)?

But did you set the IRQ priority of the USB controller also (I use the rtirq script for this)? It's the critical step--as is running an -rt kernel. Also note that I'm using the free-software radeon driver--with all the low-priority and low-performance settings I could find enabled. Using a proprietary driver is probably hopeless. The graphics card is always your worst enemy for low latency audio.

Yes, I do have a faster machine (just upgraded to FX-8350 (8-core @ 4.4Ghz)). But I was getting similar latencies my previous system, which was close to your specs (an Athlon II X4 @ 2.6Ghz).

CPU speed has less to do with latency and more to do with total DSP load capability.

I only upgraded for photo editing... with (my at least) audio software I never even came close to maxing out the Athlon--even doing full mixing/mastering at 1-3ms latency.

danboid wrote: I tried my 2i4 out under Windows for the first time at a friends house recently but didn't think to check the mixer options - thanks for pointing that out!

I actually prefer the physical controls... It's just a damn shame that the volume control doesn't affect channels 3 & 4...

Yes, USB has the highest priority in my rtirq config but still, 64 is a low as I can go before xruns attack!

I am running the prop. NV driver though so I should try with nouveau, see if things improve

I also just unpacked a brand new 2i4

But I haven't managed to get jack running with it

Using Linux Mint Nadia 14
4GB RAM
Jack config:
Input / Output Device:
hw:PCH,0 [ALC269VB Analog]
hw:PCH,3 [HDMI 0]
hw:USB,0 [USB Audio] <-- SELECTED

Input / Output Channels : 2
Sample Rate 480000 (tried 44.1 and 96 kHz too)
Periods/Buffer: 2

Logs:
Tue May 7 19:34:02 2013: Starting jack server...
Tue May 7 19:34:02 2013: JACK server starting in realtime mode with priority 85
Tue May 7 19:34:03 2013: ERROR: cannot register object path "/org/freedesktop/ReserveDevice1/Audio2": A handler is already registered for /org/freedesktop/ReserveDevice1/Audio2
Tue May 7 19:34:03 2013: ERROR: Failed to acquire device name : Audio2 error : A handler is already registered for /org/freedesktop/ReserveDevice1/Audio2
Tue May 7 19:34:03 2013: ERROR: Audio device hw:USB,0 cannot be acquired...
Tue May 7 19:34:03 2013: ERROR: Cannot initialize driver
Tue May 7 19:34:03 2013: ERROR: JackServer::Open failed with -1
Tue May 7 19:34:03 2013: ERROR: Failed to open server


Any idea wha'ts wrong?

I think it's fixed.

Instead of selecting the USB device in
Input/Output device,
I there selected "None",
and then I could select USB device in
Interface.

Seems to be working

Does the Scarlett 2i4 function completely now at 24/96 for stereo recording and playback and everything in Linux? I'm using AVLinux and I want to either get a Scarlett 2i4 or 2i2, depending on their capabilities. I just need to record and playback audio at 24/96, be able to use qjackctl and all the music software, including software that needs to be used with a2jmidid like Qsampler as well. Would it be a better choice for me to get the 2i4 or the 2i2?

Smeefer wrote:software that needs to be used with a2jmidid like Qsampler

Yep, I suspected you were asking the wrong question in the other thread. Qsampler is a softsynth. It may be internally "played" by routing midi data into it, but its output is audio. Think of it like a black box that converts midi into audio on-the-fly.

You can route midi data all over inside your computer. You need MIDI jacks on the audio interface only if you're going to connect external MIDI gear, such as a piano keyboard to manually play qsampler, or use a real hardware sampler to play your midi tracks (instead of qsampler).

Awesome, I felt that should be the case but I haven't yet used an interface that didn't have MIDI ports, so I just had to ask to make sure. Thanks!

All this talk about latency led me to another source of varying latency.

I could not see the connection between JACK settings (at least not a 1-1 connection)
and actual latency.

So I found (in Reaper) the "Performance Meter" and it reports Plug-in Delay Compensation
on each track.

This is a major source of confusion for me for a long time.

TL;DR; If you're familiar with this concept, you probably need not read further.

TL;DR; If you own a lot of plug-ins, make sure you absolutely know which ones
activate PDC, or need look-ahead.

The main problem is that not every plug-in introduces PDC

As I understand it, certain plug-ins operate in "look-ahead" mode, or, in other words,
they are buffering their sound stream in a way that requires "seeing into the future".

So, the only thing that the DAW can do is *delay everything*.

However, what is the rule here? There are plug-ins (or let's just call them effects)
such as Limiters, which usually have a look-ahead parameter. For example,
in Ableton Live, the minimum value for this is 1ms.

I was surprised to see a 1024 smp latency for a K-standard *meter* though.
(1024/48000 is roughly what, 20ms?)
So, now I always keep the "Performance" panel in Reaper docked, and periodically
check it.

But the "integer" milisecond formula is also a great revelation. (Although I've heard about
it before, I always got inconsistent results (always inconsistent, lol) depending on which
plug-ins were active.

Thanks for the info!

male wrote: ↑Mon Apr 22, 2013 6:28 pm The graphics card is always your worst enemy for low latency audio.

There are lots of variables to consider. Over the years, I've often used nVidia's 3D driver
with Reaper, a pci maudio soundcard, and the latest wine I could install, in Ubuntu Studio, Fedora, pclinuxos, and probably Mint.
Latency has never been a problem. I pretty much stumbled into an excellent existing setup for linux audio.
I found the official nvidia driver helped when dealing with complex commercial quality gui's, which sometimes failed using nouveau
or intel/amd free versions. Installing by hand, was my first serious exposure to the linux terminal, a secondary gift in my case

Those were and are pretty lean audio-centric setups, no office, no gimp, no video editors,
no games, and rather basic productions, usually less then 8 total audio tools, and without
huge track counts.

I'll guess that the system gui is also an important aspect. I've not had a kde setup since V3x rolled out,
nor the usual stock distro options, and prefer to install Enlightenment or xfce. Not always perfect,
but neither are my playing skills. (Happily, there are AVLinux versions with xfce and enlightenment.)
Cheers