# FreeBSD as an RTos? and low latency audio (xwax, mixxx)



## flyweight (May 20, 2010)

Hallo,

I have a question regardings freebsd realtime extensions,
Is freebsd capable as  an realtime os and where does it stand compared to linux?
after the ### is my message that is sent to the xwax mailing list.

I'm trying to figure out that i can use freebsd for dj-ing with timecode vinyl.
This is possible anyhow with xwax (xwax.co.uk) but the big question is. 
some people achiev a latency <3ms on (debian)linux with an realtime kernel. but i dont want to abandon my beloved FBSD.... 

On the same hardware can FreeBSD perform the same or better than linux in 
terms of latency?

Or simply is FreeBSD not capable as as realtime OS?

Thank for your time.

Gr T

###
I heard hardware specs are not so inportent as one would think. 
But anyway the machine in question is a DAW to produce music with an is an I64 
2 Quad core P45 mainboard 4GB DDR3 and 64GB SSD for the OS and 2x 2TB Sata 
300.
I really prefere freebsd over linux because of several reasons, well 
documented, lightning fast, rock solid and the most imported fact that i use 
it every day so things are ease to achieve. Linux is very nice indeed but for 
me it are several years ago that i used it. (sorry for my bad english
I know a lot of hardware is not supported on fbsd as well so most people wil 
run linux anyhow. lucky me my Maudio pci card is supported.

So my question will be:

On the same hardware can FreeBSD perform the same or better than linux in 
terms of latency?

Or simply is FreeBSD capable as as realtime OS

Is there anybody who tried a linux distro and a fbsd install on the same 
hardware?


I also will post this message on de freebsd forum as well and maybe the more 
technical people (instead of me) will have a clue.



Greets Tim

On Thursday 20 May 2010 07:49:17 you wrote:
> You can accomplish your aim by making a custom runlevel specifically for
> the use of xwax. By doing that you cut out the daemons that are running
> in your normal session. Although, the better question is what are your
> hardware specs? If you try to run on low hardware then you're obviously
> going to lag no matter which distro you use.
>
> Psyber Netik
> psyber.netik@gmail.com
>
> On 05/19/2010 04:51 AM, T. B. Astora wrote:
> > Hi There,
> >
> > Is there anybody how can give me some advise?
> > I want to install an OS only for xwax I'm familiar with freebsd my
> > soundcard with 10 ins and outs (Maudio Delta1010lt) is supported but midi
> > is not. The other option is Debian with an realtime kernel.
> >
> > My aim is to have the lowest possible latensie. I heard stories that FBSD
> > is not so good as an realtime OS. And then i heard a story of 0,3 ms on a
> > Debian box.
> >
> > So to make it short can Fbsd achieve a super low latencie?
> >
> > Thanks in advance
> >
> > Tim
> >
> > -------------------------------------------------------------------------
> >-----


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## richardpl (May 20, 2010)

Latency of what?

Speaking about MIDI there is something going very slowly but mailing list have more info.


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## roddierod (May 21, 2010)

I believe he means latency of the sound  in a real time situation.

For example, when I connect my guitar up to FreeBSD and use one of the guitar processing apps, there is a delay from the time I hit a string until the sound comes out of the speaker. Probably less than a 1 second but noticable. I believe when playing just using Audacity to record there is no delay...but I could be recalling incorrect.


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## flyweight (May 21, 2010)

The latency is about the sound comming in and out again.
For Dj-ing with control vinyl to play wav, flac and pcm tune on a cpu.
It works like this, every turtable is converted to line level (RIAA conversion) and than send out to the cpu. so 2 turtables need 4 inputs.
A program xwax for example interprets the timecode and simulate pitch and song possitions from the songs loaded in the memmory. this is than send back via the soundcards output. This way you can play digital audio files and have the control of real analog vinyl. As i like to scratch its important to have a very low latency <5ms. at high sample rates my sound card can do this the question is can Fbsd? or do i have to run a dedicated Debian with a realtime kernel?


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## flyweight (May 21, 2010)

Note, This has nothing to do with MIDI. although there are similarities.
Only a working multi i/o soundcard is needed.

Rgrds  T


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## Mage (Sep 24, 2012)

RTos is needed for best sound quality with high-end systems: vacuum tube DAC fed by S/PDIF sound output. When the output is not perfect real-time then so called "jitter" occurs which causes degradation of the sound quality. You can't hear this with average soundcards and consumer headphones but it becomes very annoying with a better system. It can make your ears hurt. I am talking about pain.

My testing results are that Windows has the best sound quality with ASIO drivers and S/PDIF output cards (sorry).
The second bests are Mac OS and FreeBSD with OSS4. They can have the same sound or they are very close to each other.
OSS3 is worse.
You can produce the worst sound with Linux. It has so much jitter that is pain to listen. I was trying for a year with so called RT kernels, oss4, alsa, highest priorities, many settings.

They are a bit hard to compare because even the hardware makes difference. I mean the not the soundcard but the computer. The testing sound cards were the same. (I have many different cards: internals, several usb cards, usb s/dif converter, external firewire card, optical output and direct s/pdif output).

FreeBSD has acceptable-good sound quality when using OSS4. However, I would be happy to read any information that might improve it more. Excellent jitter-removing hardware components are pretty expensive.


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