[LAD] jack for windows compared to linux

Benno Senoner benno.senoner at googlemail.com
Mon Jun 1 12:16:41 UTC 2009

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. 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.

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)

I did not compare the performance of LinuxSampler win32 using jack
directly as opposed piping it through the ASIO JackRouter.
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. 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
so is it regarded as stable (built from the same codebase as the linux
version?) ? did you get any positive/negative feedback from windows
users ?


2009/6/1 Stéphane Letz <letz at grame.fr>:
> Le 1 juin 09 à 07:20, Jens M Andreasen a écrit :
>> What is the performance of the jackd like in its windows incarnation.
>> Similar to Linux, better or perhaps significantly worse? Is it
>> recommendable for general purpose usage?
> In general Windows does not have so good real-time capabilities
> (compared to a RT pached Linux kernel for instance) and thus JACK
> usually cannot run at very low latencies. Otherwise the system runs
> in an equivalent manner.
> Note that on Windows an ASIO/Jack driver called "JackRouter" allows
> to use any ASIO compatible application as a JACK client. This greatly
> raise the number of applications that can be used...
>> Since this would be for cross-platform applications, I am also
>> interrested in any experience with the various graphics API's
>> available.
>> I have here a small audio application written for Win32 and
>> compiled for
>> Linux using winelib. This kind of works - at least for small projects
>> like this one - but latency is way up. The same application ported
>> to Qt
>> with jack as a KDE application runs as smooth as one could ever
>> request.
>> Would this then be a simple matter of running ./configure and make on
>> the output from KDevelop to get it to compile and run on Windows as
>> well?
> This should work, but could require a bit of work to adapt the .pro
> fle or something.
> Stéphane
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