Re: [Jack-Devel] Using Jack

On 18/03/2014 07:41, Stéphane Letz wrote:
> Lack of time to test and answer, possible more time in april.
>

Hi Yves,

Since Stephane is unavailable at present I can give you a very rough 
idea of how we start Jack from within Mixbus.  However, we don't support 
midi (within Windows) so it might not be relevant to your situation.  
Please bear in mind what Stephane said previously... setting your app up 
as a Jack server is NOT a good idea - because if other apps use Jack 
(like Mixbus, for example) they would use the version provided by your 
app.  So, when your app eventually shuts down, anything else that was 
using Jack would break!  The correct way to use Jack is to launch it as 
an external server and let Jack decide whether & when to shut itself down.

In Mixbus, we seem to create a file called ".jackdrc" (notice that it 
begins with a ".", rather than a "j").  Basically, that file contains a 
list of commands for starting Jack.  Typical file contents might look 
like this:-

"C:\Program Files\Jack\jackd.exe" -S -p 512 -T -d portaudio -r 48000 -p 
512 -P  "ASIO::ASIO4ALL v2"  -C  "ASIO::ASIO4ALL v2"

The first parameter is a path to the Jack server.  "-S" means to start 
Jack in synchronous mode (I believe this is mandatory on Windows).  Not 
sure what the (two) "-p" parameters are but at least one of them must be 
the buffer size (512 in this example). "-T" means "temporary" (Jack will 
shut itself down automatically when it detects that nothing is connected 
to it any more).  "-d portaudio" is the audio driver (portaudio is 
almost always the driver for Windows - so you'll need to install that 
too.  For testing purposes you can use "-d dummy").  "-r 48000" is the 
audio sample rate.  "-P" then gives us the Playback device and "-C" 
gives us the Capture device (input device).

If you typed that complete line into a command prompt (assuming you'd 
already installed ASIO4ALL) Jack would launch and would use it.

Having described all that....  I've no idea what Jack actually does with 
that .jackdrc file.  Stephane or Paul will undoubtedly know. It looks 
like the file needs to be in the user's personal folder (e.g. 
C:\Documents and Settings\<user_name>) but I'm not sure how we tell Jack 
to look for it there.  Simply starting Jack with no parameters doesn't 
seem to make it search for .jackdrc - so I'm not sure how that happens.  
If I manage to get some spare time this week, I'll try to find out.

John

1395131598.28110_0.ltw:2, <532804A7.7020805 at tiscali dot co dot uk>