[LAD] jack for windows compared to linux

[Stéphane Letz]

Le 1 juin 09 à 14:16, Benno Senoner a écrit :

> Hi Stephane,
> what kind of latencies did you achieve with jack on windows ?
> some time ago I tried to pipe LinuxSampler Win32 and Kontakt2 through
> jack using the ASIO router and ASIO backend for jack (or does it go
> thorugh portaudio which in turn uses ASIO ?  I don' remember exactly,
> it was 8-12 months ago)
> and compared to LinuxSampler or Kontakt using ASIO directly jack was
> much worse, each few secs I got a dropout under load.
> And the latency of the asio router for jack was always 512 frames.

JackRouter reflect the currently chosen JACK server buffer-size for  
ASIO clients.


> I
> don't remember what number of frames I used for jack out but
> I tried several combinations and in no way I could match the latency
> and reliability of using ASIO directly.
> As hardware I was using a Dell laptop with ASIO4ALL (I think it's
> intel hidef audio chip)
>
> Now the question is: was the weak link the ASIO router for jack, was
> it portaudio or is it the WIN32 IPC which is unreliable ?
> AFAIK multithreaded VST hosts do use IPC calls to to support multicore
> CPUs and it seems capable of achieving low latencies.

Difficult to say without more precise "profiling" and tests...

>
> There is some discussion going on on the LinuxSampler forum about the
> upcoming LinuxSampler version (the beta is already available)
> and an user asked it the next windows version will come with jack
> support compiled in.  (it works with jack win32 too)
> http://bb.linuxsampler.org/viewtopic.php? 
> f=2&t=339&sid=ed3163f7f87cfe0e45030e4bbf802fab&start=20
>
> I did not compare the performance of LinuxSampler win32 using jack
> directly as opposed piping it through the ASIO JackRouter.

This would be interesting to test, to see if the JackRouter component  
is the "weak" part or not...


> What do you think Stephane, can native jack clients on windows achieve
> performance which is almost at par as native ASIO apps ?
> If we release LinuxSampler with jack support we have probably to ship
> libjack (otherwise the app does not start)  with the sampler and it
> could be that it conflicts with an
> already installed jack.

Well I also recently had this kind of "weak" link requirement for  
libjack on Linux. I think OSX supports some kind of weak linking with  
any compiled framework, but the situation is less clear on Windows on  
Linux. A possible solution would be to provide a special  
"libweakjack" library with the appropriate bahaviour for that.


> So probably at this point the official LS will
> be released without jack compiled in but it would be nice if jack will
> soon become an established method audio/MIDI routing
> on windows too.
> Stephane, what are your plans regarding the windows platform ? I see
> that jack1.9 for windows can be downloaded from jackaudio.org download
> page
> so is it regarded as stable (built from the same codebase as the linux
> version?) ?

Same codebase yes.


> did you get any positive/negative feedback from windows
> users ?

No "stablility problems" feeback AFAICS, but people are maybe not  
using the system in real low-latencies situations.

Stephane