[LAD] [Jack-Devel] Towards a truely realtime capable FOSS audio distribution | A guide to the Jack Source Code

Stéphane Letz letz at grame.fr
Thu Jul 24 20:55:26 UTC 2008

Le 24 juil. 08 à 22:23, micu a écrit :

> Hello everybody,
> my name is micu and I study computer science at the Dresden  
> University of
> Technology. During an internship at the operating systems chair of the
> university, I ported ALSA to the chairs operating system DROPS aka  
> [1,2]. To let ALSA talk to the hardware and provide to it the usual  
> linux
> kernel environment DDEKit / DDELinux [3] were used. As a kernel- 
> userland
> interface I wrote a very small emulation layer, which makes it  
> possible to
> link SALSA-lib [4] against the ALSA "kernel" part.
> So right now, we have a somewhat stable ALSA server running in  
> userland on top
> of DROPS without changing ALSA or the SALSA-lib source code.
> I have been continuing this project within my diploma thesis. The  
> remit of the
> thesis can be found here [5]. It is the goal of the thesis to take  
> some steps
> towards a truly realtime capable (meaning with time constraints to be
> guaranteed) FOSS audio distribution. Here [6] you can see a raw  
> version of my
> requirements definition.
> The architecture we are going to use is --- how could it be  
> different :) ---
> Jack or Jackdmp (with a strong bias towards Jackdmp). To get the  
> mess out of
> my head, I wrote a short guide [7] to the Jack source code. It is a  
> pretty
> raw version and it isn't finished in any way yet; but I won't work  
> on it any
> longer. Nevertheless, it might be helpful to other developers new  
> to Jack.
> Therefore, if you will, you may get it under any license you wish
> (attribution of the author is appreciated :) to publish and improve  
> it.
> Of course, the long term goal of the project won't be met to any  
> extent during
> my thesis and I have no idea, if this project will be continued  
> here at the
> university. Neither do I know, whether I will have time to work on it
> afterwards.
> To make a long story short: I would like to ask my first three  
> questions....
> so far :)
> 	1.) Do you agree on having a truly real-time capable architecture  
> in the FOSS
> audio world would be a really great thing --- and would you say,  
> getting such
> a thing maybe could get a (major) goal of the pro audio FOSS  
> community?

It is certainly an interesting idea to better caracterize and  
understand how a complex system works regarding real-time  
capabilities. Some new tools are to be developed to understand what  
happens when a complex graph of jack clients works for example. My  
feeling it that it would be a desirable goal.

> 	2.) Concerning our Jack vs. Jackdmp decision: http:// 
> jackaudio.org/ says,
> Jackdmp is going to be Jack 2.0. How likely and how soon do you  
> think is this
> going to happen?

Difficult to say, but I stongly suggest to have a look at jack2 SVN  
code ( jackdmp 1.90 version). New code and ideas are now developed on  
this code base.

> 	3.) I guess, there is a very minor bug in the lines 236, 237 of
> libjack/driver.c, svn revision 2734: The type castings should be  
> switched.

A patch is always better.
> Thanks a lot in advance and please excuse my bad english :(.


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