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#1 2016-08-06 17:32:55

frankb
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Registered: 2016-07-02
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[SOLVED] does bunsen use real time kernel?

Im using audio software and was told i need to use a real time kernel. Thanks

Last edited by Head_on_a_Stick (2016-08-21 00:03:55)

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#2 2016-08-06 18:18:31

Head_on_a_Stick
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Re: [SOLVED] does bunsen use real time kernel?

You can try the rt-patched kernel image from the jessie-backports repository:
https://packages.debian.org/jessie-back … e-rt-amd64

Add the jessie-backports repositories, as per this guide:
https://backports.debian.org/Instructions/

Then update your package database and install the new kernel:

sudo apt update
sudo apt install linux-image-rt-amd64/jessie-backports

“Et ignotas animum dimittit in artes.” — Ovid, Metamorphoses, VIII., 18.

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#3 2016-08-20 19:43:33

frankb
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Re: [SOLVED] does bunsen use real time kernel?

thanks!

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#4 2016-08-20 19:51:05

ohnonot
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Re: [SOLVED] does bunsen use real time kernel?

there's a longstanding discussion whether a rt-kernel is even required for media production with more recent kernels (whatever "more recent" means; i think this statement has been around since 3.x).
some say it isn't. but i'm not sure what the arguments either way are.

expert opinions welcome?

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#5 2016-08-21 00:01:35

Head_on_a_Stick
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Re: [SOLVED] does bunsen use real time kernel?

^

wiki.linuxaudio.org wrote:

Kernels >= 2.6.31 seem to work pretty good without RT patch, also for real-time pro audio usage. It's not strictly necessary anymore to install a real-time ('rt') kernel to get good results. Although the best results are still expected when using a real-time kernel. Try it, test it and decide for yourself.

http://wiki.linuxaudio.org/wiki/system_configuration

There are other provisos listed though.


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#6 2016-08-21 05:41:01

ohnonot
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Re: [SOLVED] does bunsen use real time kernel?

thanks for quoting that back at me, HoaS.

does somebody actually do A/V production and can tell us what that is all about.

i mean, WHY do kernels ">= 2.6.31 seem to work pretty good without RT patch", and why "best results are still expected when using a real-time kernel"???

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#7 2016-08-21 08:06:38

Snap
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Registered: 2015-10-02
Posts: 465

Re: [SOLVED] does bunsen use real time kernel?

I think this clarifies a lot.

https://askubuntu.com/questions/126664/ … 948#205948

Basically it says that if you use a powerful multi-core machine (CPU) you probably won't see any real benefit. In fact it can be detrimental performance wise. But if you computer is not that great or hi-end, low latency kernels might be exactly what you need to use for media production.

Most audio hobbists out there don't use Xeon processors. The best ones for the purpose (all-at-once server architechture). Not even i7. So most should choose to go with low latency kernels to get a high throughput at low latency. Plainly said Low latency, preempt or RT kernels are workarounds for the penny pinching audio "workstations" that most of us are using.

Last edited by Snap (2016-08-21 08:31:25)

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#8 2016-08-21 09:36:17

ohnonot
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Re: [SOLVED] does bunsen use real time kernel?

thanks for the link!
reading it, and the blog article, reminded me again of the old confusion.
now we already have 3 terms: lowlatency, preempt, realtime... and can somebody say with certainty what the difference between those is, where linux kernels are concerned?

anyhow, after reading, it becomes clear that the kernel is not the only thing that wants some tweaking to make a weak machine into a usable A/V production machine.


Snap wrote:

Plainly said Low latency, preempt or RT kernels are workarounds for the penny pinching audio "workstations" that most of us are using.

erm, sorry i don't understand that.
what are these "penny pinching audio workstations"?

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#9 2016-08-21 14:28:45

frankb
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Registered: 2016-07-02
Posts: 25

Re: [SOLVED] does bunsen use real time kernel?

im probably going to move to avlinux. it is incredibly fast. i do audio programing (supercollider)
just the live usb is insane

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#10 2016-08-22 08:44:19

Snap
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Posts: 465

Re: [SOLVED] does bunsen use real time kernel?

reading it, and the blog article, reminded me again of the old confusion.
now we already have 3 terms: lowlatency, preempt, realtime... and can somebody say with certainty what the difference between those is, where linux kernels are concerned?

IIRC, Real time is what we want to achieve the lowest possible latency. It's real time, so there's no latency. But a real time kernel tends to be unstable. That's why kernels are typically delayed. Otherwise we all would be using RT kernels for every purpose. Obviously we don't do that for a good reason. We want stable kernels. For media production if we feel we need to reduce the latency, it's often a better choice to use a less radical solution. A low latency (or simply preempt) kernel. They're capable of an acceptable low latency and good stability compared with RT ones. They are usually fast enough for us to be able to discern any latency in most cases.

erm, sorry i don't understand that.
what are these "penny pinching audio workstations"?

Probably me neither... LOL. What I've tried to say is that an ideal dedicated audio workstation is an expensive machine. Fisrt, it should be dedicated. Or at least having a dedicated OS plus a set of hard drives. It should be a server type machine (a Xeon CPU with an appropriate mobo, or the poorman's solution; an AMD FX set). Having the fastest possible clock speed and at the same time the highest CPU count in a single chip. Who uses such a machine? Not many. They're really expensive and out of reach for most of us. Most audio hobbists use just a decent (pretty limited) laptop and that's it. That's why I said penny pinching DAWs.

I don't remember noticing any hint of latency when I used dual Xeon servers for audio production. I don't have them any more. I currently have an AMD FX and cannot tell a difference using either regular or preempt kernels. I use preempt anyway. but, honestly. That's pure inertia. Not a real reason I've found so far. In my experience it all depends on your rig.

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#11 2016-08-23 05:13:34

ohnonot
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Re: [SOLVED] does bunsen use real time kernel?

thanks again, snap.

so afaiu, preempt is the technique used, low latency is what it achieves, and realtime is the ideal?
so all 3 terms are about reducing latency.

it seems to me reducing latency is very important when you use your computer in live situations, or when you e.g. want to record a human-produced track on top of some existing tracks.

in all other cases (composition, downmixing) latency matters to a much lesser extent, e.g. when your volume meter does not wiggle in sync with the sound you're hearing.
the only thing that really matters is that you don't have overflows or dropouts.
which is mostly achieved by
a) having a sufficiently fast cpu and enough RAM
b) not using too many extra processes
c) (mystery ingredient): some setting in the kernel (?) that prioritizes audio processing

now in my opinion, c) is not exactly the same as "low latency" but maybe it is what preempt actually does?

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#12 2016-08-23 07:28:06

Snap
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Registered: 2015-10-02
Posts: 465

Re: [SOLVED] does bunsen use real time kernel?

so afaiu, preempt is the technique used, low latency is what it achieves, and realtime is the ideal?
so all 3 terms are about reducing latency.

That's it. preempt has to be enabled first into the kernel. Then tweaked more or less conservative to reduce latency.

it seems to me reducing latency is very important when you use your computer in live situations, or when you e.g. want to record a human-produced track on top of some existing tracks.
[...]
c) (mystery ingredient): some setting in the kernel (?) that prioritizes audio processing

You are right again. Processing priority is the other key to audio (erm... multimedia) setups. latency and priority are the battle horses. And there's a ton of drawbacks and things to consider, which uses to make it a nightmare to get a well configured DAW rig. Things like using PS/2 mice and keyboards when using RT or LL kernels (USB is too slow for the purpose and induces errors and jitter). Never using CPU governors or Power saving/management or at least put the under very low priority so they don't interfere. Better disable network for DAW usage, at least when not actually needed. Proprietary drivers use to play bad with low latency kernels, etc, etc, etc...

Regarding tracking and playback. What you said. This quote must be a tattoo for audio guys, or at least a poster on their walls.

Live audio does not benefit from multicore processing, in fact it degrades performance. What you want is the fastest single core clock speed you can get, so a 3.6GHz processor with 2 cores will perform better than a 4 core 2.2GHz processor for live audio.

I realize that this will seem totally off the wall for computer gamers and benchmarkers, but live audio needs to come in, get processed and go out with as little latency as possible. Audio is a continuous stream of data, which does not thread out easily.

In a studio environment with recorded tracks, this is not nearly as big of an issue as audio does not have to be processed in real time, it just all needs to be synched and if everything is delayed at the same rate, you have nothing to reference it to.

-Andy Hamm.

The best settings for live audio/tracking/capturing are not very good for playback/editing/mixing/mastering and viceversa. That's why high-end studios usually have different and independent machines for tracking and mixing/whatever. The rest of us mortals have to make compromises with our machines to get decent performance in every situation. Back in the day I used a dual Xeon HP workstation for the delayed stuff and an Alesis HD24XR for tracking. That was great stuff! I still have the HD24 around but hardly ever used. Currently I only use a decent rig with an AMD FX8350. An eight core CPU @ 4.2 GHz clock speed. Which makes it quite good for both purposes. But I don't make a living of this any more, so more than enough for some occasional fun.

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#13 2016-08-25 05:02:12

ohnonot
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Registered: 2015-09-29
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Re: [SOLVED] does bunsen use real time kernel?

thanks again!

all in all, i think it's possible to do some decent audio production on a consumer product these days, provided you dual-boot into a setup specifically for that purpose.

good tip about not using usb peripherals, btw.

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#14 2016-08-26 02:52:03

Snap
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Registered: 2015-10-02
Posts: 465

Re: [SOLVED] does bunsen use real time kernel?

^ True. Current mid-range computers can make quite powerful home studio DAWs if setup well. Typically at home, you don't need to print 24 tracks at once with five or six different foldbacks (including your own (control) monitoring), realtime reverb for the musicians plus some other effects, etc... Most of the times it's just one or two mics or line inputs and not much else going. Then going back to delayed stuff, hyperthreading and tons of RAM if possible.

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